Lubricating and low friction coefficient coating composition for rigid substrates

Abstract

The present invention provides a coating composition for coating a rigid substrate, the coating composition comprising: a binder resin; a lubricating component, the lubricating component comprising a wax; and a solvent. The coating composition can further include a silicone resin. The binder resin is at least one of a polyamideimide, an epoxy resin, a silicone polyester, and a polyurethane resin. The wax is at least one of carnauba wax, polyethylene wax, polypropylene wax, polyamide wax and Fischer-Tropsch wax. The coating composition is wear resistant and is substantially free of perfluoroalkyl species (PFAS) and N-methylpyrrolidone (NMP).

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 63 / 512,505, filed July 7, 2023, entitled “LUBRICATING AND LOW COEFFICIENT OF FRICTION COATING COMPOSITION FOR RIGID SUBSTRATES,” and U.S. Provisional Application No. 63 / 591,146, filed October 18, 2023, entitled “LUBRICATING AND LOW COEFFICIENT OF FRICTION COATING COMPOSITION FOR RIGID SUBSTRATES,” both of which are incorporated by reference in their entireties.

[0003] Government License Rights

[0004] This invention was made with government support under Government Contract No. W911NF-17-2-0227 awarded by the U.S. Army Contracting Command on behalf of the U.S. Army Research Laboratory (ARL). The government can have certain rights in the invention. TECHNICAL FIELD

[0005] The present disclosure relates to a lubricating coating composition having a low coefficient of friction that can be applied to rigid substrates. BACKGROUND

[0006] Rigid metal parts of mechanical equipment can experience a variety of contact forces and frictional forces that can lead to wear and deterioration over time of use. Coatings can be applied to these metal parts to enhance wear resistance, prevent premature failure, and / or dampen noise. Known coatings often contain perfluoroalkyl substances (PFAS) and / or solvents such as N-methyl pyrrolidone (NMP) that are increasingly subject to stricter regulations.

[0007] Accordingly, improvements to such coatings are desired. SUMMARY

[0008] The present disclosure provides a coating composition for rigid substrates, the coating composition comprising: a binder resin; a lubricating component comprising a wax; and a solvent. The binder resin is selected from the group consisting of polyamideimide, epoxy, silicone polyester, and polyurethane resins. The wax can be at least one of carnauba wax, polyethylene wax, and Fischer-Tropsch wax. The lubricating component further comprises a silicone resin. The coating composition is wear resistant and substantially free of perfluoroalkyl substances and N-methyl pyrrolidone.

[0009] In one form thereof, the present disclosure provides a method of coating a rigid substrate, the method comprising: applying a coating composition to the rigid substrate, and curing the coating composition at a temperature of 170°C to 240°C. The coating composition comprises: a binder resin; a lubricious component comprising a wax; and a solvent.

[0010] In another form thereof, the present disclosure also provides a coated rigid substrate comprising a rigid substrate and a coating on the rigid substrate. The coating on the rigid substrate comprises a binder resin and a lubricious component comprising a wax. BRIEF DESCRIPTION OF DRAWINGS

[0011] The above and other features and advantages of the present disclosure and the manner of attaining them will become more apparent, and the disclosure itself will be better understood by reference to the following description taken in conjunction with the accompanying drawings. The above and other features of the present disclosure can be used in any combination or arrangement.

[0012] Figure 1 is a graph of the results of a friction test illustrating the coefficient of friction versus time comparing coating 1 and inventive coatings 1-3;

[0013] Figure 2 is a graph of the results of a friction test illustrating the coefficient of friction versus time comparing coating 1 and inventive coatings 3-4;

[0014] Figure 3 is a graph of the results of a friction test illustrating the coefficient of friction versus time comparing coating 2 and inventive coatings 3 and 5;

[0015] Figure 4 is a graph of the results of a friction test conducted at room temperature illustrating the coefficient of friction versus time comparing coating 3 and inventive coatings 6-11;

[0016] Figure 5 is a graph of the results of a friction test conducted at room temperature illustrating the coefficient of friction versus time comparing coating 4 and inventive coatings 12-15; and

[0017] Figure 6 is a graph of the results of a friction test conducted at an elevated temperature of 150°C illustrating the coefficient of friction versus time comparing coating 5 and inventive coatings 16-20.

[0018] In several views, corresponding reference numerals indicate corresponding parts throughout the several views. The examples set forth herein demonstrate the present disclosure and such examples should not be interpreted as limiting the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0019] The present disclosure provides a coating composition having a low coefficient of friction that can be applied to a rigid substrate.

[0020] I. Definitions

[0021] For purposes of the following detailed description, it is to be understood that the disclosure can assume various alternative arrangements and step sequences, except where expressly indicated otherwise. Also, other than in any operating examples, or where otherwise indicated, all numbers

[0022] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0023] Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges of the same numerical precision subsumed

[0024] The use of a singular herein includes a plural, and the use of a plural herein includes the singular, unless explicitly otherwise stated. Also, unless explicitly stated otherwise, the use of "or" means "and / or", even though "and / or" can be explicitly used in some instances.

[0025] "Wax" is used herein to describe a synthetic or naturally occurring material formed from a mixture of alkanes of various chain lengths and / or modified alkanes that also include other functional groups in the chain, such as esters and / or amines, and can exhibit phase change properties, where the wax tends to be solid at room temperature (20°C), has a melting point above about 40°C, and is able to absorb heat while showing little volume change during melting.

[0026] “Brazilian Carnauba Wax” is a naturally occurring wax that includes fatty esters (40 wt%), 4-hydroxy cinnamic acid diesters (21.0 wt%), omega-hydroxy carboxylic acids (13.0 wt%), and fatty alcohols (12 wt%) as an exemplary blend.

[0027] “Fischer-Tropsch (FT) wax” is a pure synthetic polymer of carbon monoxide and hydrogen that can be considered a mineral wax. FT wax is a long-chain aliphatic hydrocarbon with relatively short side chains.

[0028] “Polyethylene wax” is a low molecular weight synthetic polymer containing ethylene monomer chains. Polyethylene wax has a typical melting point in the range of 90 to 150 °C.

[0029] “PFAS” is used herein to describe per- and polyfluorinated substances, including synthetic organic fluorine compounds with multiple fluorine atoms attached to an alkyl chain, such as perfluorinated monomers and oligomers, such as perfluorooctanoic acid.

[0030] “Wet” coating composition is used herein to describe a liquid coating composition prior to curing.

[0031] “Dry” coating composition is used herein to describe a coating composition after curing.

[0032] II. Coating Composition

[0033] The present disclosure provides a PFAS-free coating composition that provides increased abrasion resistance and lubricity compared to traditional PFAS coating compositions. The coating composition can include a binder resin, a lubricating component, and a solvent.

[0034] A. Binder Resin

[0035] The binder resin provides adhesion to the substrate and improves mechanical properties such as elongation, and can cure either on its own or with the help of a curing agent. The binder resin can allow the coating to follow the elongation of the coated belt during operation without cracking or peeling or suffering from thermal mechanical fatigue. The binder resin can be interchangeably referred to herein as a ‘binder’, ‘resin binder’, or ‘binder resin’, ‘base’, or ‘binder system’, and depending on the amount of lubricating component required, the binder resin can provide the bulk of the coating of the present invention when applied to the substrate.

[0036] The binder resin of the present disclosure can be selected from polyamide imides, epoxy resins, silicone polyesters, polyurethanes, and combinations thereof.

[0037] The coating composition provided by the present disclosure can include a binder resin in a weight percent of 20 wt%, 25 wt%, 30 wt%, 35 wt% to 40 wt%, 50 wt%, 60 wt%, 80 wt%, or any range including any two of these values as endpoints, such as 20 wt% to 80 wt%, 25 wt% to 60 wt%, 30 wt% to 50 wt%, or 35 wt% to 40 wt%, where the weight percent is based on the total weight of the “wet” coating composition.

[0038] The binder resin can be present in the cured coating composition in an amount of 35 wt%, 55 wt%, 70 wt%, 75 wt% to 80 wt%, 85 wt%, 90 wt%, 98 wt%, or any range including any two of these values as endpoints, such as 35 wt% to 98 wt%, 55 wt% to 90 wt%, 70 wt% to 85 wt%, or 75 wt% to 80 wt%, where the weight percent is based on the total weight of the “dry” coating composition.

[0039] The binder resin can be present in the cured coating composition in a volume of 40%, 60%, 70% to 80%, 90%, 98%, or any range including any two of these values as endpoints, such as 40% to 98%, 60% to 90%, or 70% to 80%, where the volume percent is based on the total volume of the “dry” coating composition.

[0040] i. Polyamide-imide

[0041] The binder resin of the present disclosure can be a polymeric binder resin including a polyamide-imide (PAI). Polyamide-imides (PAI) can be thermoset or thermoplastic amorphous polymers and generally have excellent mechanical, heat, and chemical resistance properties. Suitable polyamide-imides can include polyamide-imides produced by Solvay Specialty Polymers under the trademark Torlon. The polyamide-imide polymers can be formed from isocyanate and TMA (trimellitic anhydride) in N-methyl-2-pyrrolidone (NMP). Polyamide-imides can have the desirable properties of both polyamides and polyimides, such as high strength, melt processability, excellent high heat capability, and a wide range of chemical resistance. The polyamide-imide polymers can be processed into a variety of forms, from injection or compression molded parts and castings to coatings, films, fibers, and adhesives. Typically, these articles reach their maximum properties through a subsequent thermal curing process.

[0042] ii. Epoxy resin

[0043] The adhesive resin can be an epoxy resin. Epoxy resins can include polymers containing epoxy groups and exhibit mechanical properties as adhesives, plastics, and coating materials. The adhesive resin can be an epoxy novolac resin. Epoxy novolac resins are phenol-formaldehyde resins modified at the phenolic hydroxyl groups to contain epoxy functional groups, which increases the cross-linking ability of the resin. Suitable epoxy resins can include: the EPON product line from Resolution Products (e.g., Epon 828, bisphenol A-epichlorohydrin epoxy resin and / or a blend of this resin with a difunctional epoxide reactive diluent such as neopentyl glycol diglycidyl ether, resorcinol diglycidyl ether, and cyclohexane dimethanol diglycidyl ether; Epon DPL862, bisphenol F-epichlorohydrin epoxy resin); the EPALLOY product line from CVC Thermoset Specialties (e.g., EPALLOY 8250, epoxy novolac resin); Ciba Geigy’s Araldite EPN 1139; and Olin’s DEN 432, DEN 438, DEN 439, and DEN 440. Suitable non-aromatic epoxy resins include diglycidyl ethers of hydrogenated cyclohexane dimethanol and hydrogenated bisphenol A-type epoxy resins, such as: the EPON product line from Resolution Products (e.g., EPON 1510, EPON 4080E, Heloxy 107, and EPON 1513, hydrogenated bisphenol A-epichlorohydrin epoxy resin); Monsanto’s santolink LSE-120; Pacific Anchor’s epodii 757 (cyclohexane dimethanol diglycidyl ether); Ciba Geigy’s Araldite XUGY 358 and PY 327; Rhone-Poulene’s epirez 505; Reichold’s aroflint 393 and 607; Momentive’s EPI-REZ; Kukdo’s epoxy resins; Aditya Birla’s epoxy resins; and Union Carbide’s ERL 4221. TM

[0044] iii. Silicone polyesters

[0045] ​The silicone polyester resin can be a copolymer prepared by polycondensation of a diol with a diacid, which is grafted with an alkoxyl or hydroxyl functional siloxane oligomer or monomer. The silicone polyester resin can be supplied in dry form or dissolved in a solvent such as, but not limited to, methoxypropyl acetate, toluene, xylene, butyl acetate, ethyl acetate, and methyl isobutyl ketone. Suitable silicone polyesters can include Chempol 806-1332, Silicoftal HTF, Silicoftal HTL, Silicoftal HTT, Silicoftal HTW3, Silicoftal Non-stick 60, SW weather XL, and Akzo Cream-A-star.

[0046] iv. Polyurethanes

[0047] Polyurethane resins can be prepared by reacting a polyester polyol, polycarbonate polyol, polyether polyol, or acrylic polyol with a polyisocyanate and an acidic functional polyol such as dimethylol propionic acid such that the NCO / OH ratio is greater than 1 : 1, resulting in an NCO functional prepolymer. The terminal isocyanate can then be reacted to produce a terminal COOH group using one of a variety of methods described below. Acid groups introduced in the first stage of polyurethane preparation are considered internal COOH groups, while acid groups introduced via reaction of the prepolymer NCO end groups are considered terminal COOH groups. The acid functional polyurethane polymer can be neutralized with an amine and dispersed into water. Suitable polyurethane resins can include Desmolac from Covestro, GN-410 from Polyval, Sancure 2310 from Lubriol, Sancure 20072 from Lubriol, Aptalon 8300 from Lubriol, Aptalon M8120 from Lubriol, Hydran Wi from DIC, Hydran Ap from DIC, Hydran Cp from DIC, Vondic from DIC, RIMLINE from Huntsman, VITROX from Huntsman, and PU Binder 1128.

[0048] B. Lubricious Component

[0049] Another component of the coating composition is a lubricious component. The role of the lubricious component is to reduce friction at the surface of the coating when the coated substrate is in contact with another component.

[0050] The lubricious component can comprise a wax and optionally a silicone resin.

[0051] The coating compositions of the present disclosure can have a weight ratio of the total amount of lubricating components to dry binder resin and dry lubricant that is 0.001, 0.005, 0.01 to 0.10, 0.25, 0.5, or any range including any two of these values as endpoints, such as 0.001 to 0.50, 0.005 to 0.25, or 0.01 to 0.10.

[0052] i. Waxes

[0053] The coating compositions provided by the present disclosure can include waxes in a weight percentage of, for example, 0.05 wt.%, 0.5 wt.%, 1 wt.% to 2 wt.%, 5 wt.%, 10 wt.%, or any range including any two of these values as endpoints, such as 0.05 wt.% to 10 wt.%, 0.5 wt.% to 5 wt.%, or 1 wt.% to 2 wt.%, where the weight percentage is based on the total weight of the “wet” coating composition.

[0054] The waxes can be present in the cured coating composition in an amount of 0.1 wt.%, 1 wt.%, 10 wt.% to 20 wt.%, 30 wt.%, 35 wt.%, or any range including any two of these values as endpoints, such as 0.1 wt.% to 35 wt.%, 1 wt.% to 30 wt.%, or 10 wt.% to 20 wt.%, where the weight percentage is based on the total weight of the “dry” coating composition.

[0055] The waxes can be present in the cured coating composition in a volume percentage of 0.5%, 5%, 10% to 20%, 30%, 45%, or any range including any two of these values as endpoints, such as 0.5% to 45%, 5% to 30%, or 10% to 20%, where the volume percentage is based on the total volume of the “dry” coating composition.

[0056] a. Carnauba Wax

[0057] Carnauba wax is a natural wax that comes from the leaves of the carnauba palm tree (i.e., Copernicia cerifera), which is native to the northeast of Brazil. Carnauba wax comprises aliphatic esters, diesters, 4-hydroxy cinnamic acid, w-hydroxy carboxylic acids, and fatty alcohols.

[0058] The carnauba wax can comprise particles having a median diameter or D50 of less than 15 µm, less than 12 µm, less than 8 µm, less than 6 µm, less than 4 µm, less than 2 µm, less than 1 µm, less than 0.5 µm, or less than 0.1 µm, as determined by dynamic light scattering measured by Mie scattering and Fraunhofer diffraction techniques as practiced in ISO 13320-1.

[0059] b. Polyethylene wax

[0060] Polyethylene wax is a low-molecular-weight synthetic wax composed of ethylene monomer chains. Polyethylene wax can be synthesized in various ways, such as through direct polymerization of ethylene. As measured by GPC (gel permeation chromatography), the molecular weight of polyethylene wax can range from 1,000 to 50,000 g / mol.

[0061] The lubricating component may comprise polyethylene wax in powder form. As measured by dynamic light scattering techniques of Mie scattering and Fraunhofer diffraction according to ISO 13320-1, the powdered polyethylene wax may comprise particles having a median diameter or D50 of 4 µm, 5 µm, 6 µm to 8 µm, 10 µm, 12 µm, or any range using any of the aforementioned values ​​as endpoints (such as 4 µm to 12 µm, 5 µm to 10 µm, or 6 µm to 8 µm).

[0062] c. Fischer-Tropsch wax

[0063] Fischer-Tropsch wax is a synthetic wax produced by the polymerization of carbon monoxide and hydrogen. The side chains of Fischer-Tropsch wax contain straight-chain alkanes and do not contain double bonds.

[0064] The lubricating component may comprise Fischer-Tropsch wax in powder form. As measured by dynamic light scattering techniques of Mie scattering and Fraunhofer diffraction according to ISO 13320-1, powdered Fischer-Tropsch wax may comprise particles having a median diameter or D50 of 1 µm, 2 µm, 4 µm to 6 µm, 8 µm, 10 µm, or any range using any of the foregoing values ​​as endpoints (such as 1 µm to 10 µm, 2 µm to 8 µm, or 4 µm to 6 µm).

[0065] d. Polypropylene wax

[0066] Polypropylene wax (PP wax) is a synthetic wax derived from the thermoplastic polymer polypropylene. Polypropylene wax is typically produced by polymerizing propylene monomers to create a material with waxy properties.

[0067] e. Polyamide wax

[0068] Lubricating components may include polyamide waxes. Polyamide waxes (PA waxes) are synthetic waxes derived from polyamide resins. Polyamides are polymers with repeating amide bonds in their molecular structure. Due to their excellent mechanical properties, chemical resistance, and thermal stability, they are frequently used in various industries. Polyamide waxes are typically produced by the polymerization of amide monomers, resulting in solid or semi-solid materials with a waxy texture.

[0069] iv. Organosilicon resin

[0070] The coating composition may contain at least one silicone resin. The silicone resin may contain a silsesquioxane polymer of the general formula: (C6H5SiO)1.5 ) x

[0071] Where x is an integer greater than approximately 4.

[0072] The coating composition may contain a total amount of silicone resin of 1 wt%, 2 wt%, 4 wt% to 6 wt%, 8 wt%, 10 wt%, or any range including any two of the foregoing values ​​as endpoints (such as 1 wt% to 10 wt%, 2 wt% to 8 wt%, or 4 wt% to 6 wt%), wherein the weight percentage is based on the total weight of the “wet” coating composition.

[0073] After the coating is applied and cured, the silicone resin may be present in the coating composition in a total amount ranging from 15 wt%, 20 wt%, 25 wt% to 30 wt%, 35 wt%, 40 wt%, or any range including any two of the foregoing values ​​as endpoints (such as 15 wt% to 40 wt%, 20 wt% to 35 wt%, or 25 wt% to 30 wt%), wherein the weight percentage is based on the total weight of the “dry” coating composition.

[0074] The silicone resin may be present in the cured coating in a total amount ranging from 10 vol%, 20 vol%, 25 vol% to 30 vol%, 35 vol%, 45 vol%, or any range including any two of the foregoing values ​​as endpoints (such as 10 vol% to 45 vol%, 20 vol% to 35 vol%, or 25 vol% to 30 vol%), wherein the volume percentage is based on the total volume of the “dry” coating composition.

[0075] Suitable silsesquioxane polymers may include poly(alkyl silsesquioxane) and poly(aryl-alkyl silsesquioxane).

[0076] a. Poly(alkylsilsesquioxane)

[0077] A representative structure of poly(alkylsilsesquioxane) is shown in Formula I:

[0078]

[0079] Formula I

[0080] R can be an alkyl substituent, such as methyl, ethyl, propyl, butyl, octyl, etc.

[0081] Suitable poly(alkylsilsesquioxane) silicone resins may include poly(methylsilsesquioxane) as shown in Formula II.

[0082]

[0083] Formula II

[0084] The poly(alkylsilsesquioxane) used herein can be obtained in the form of solid spherical beads. The beads can be dispersed together with other components of the coating composition. The size of the beads can be 1 µm, 2 µm, 4 µm to 6 µm, 8 µm to 10 µm, or any range using any of the foregoing values ​​as endpoints (such as 1 µm to 10 µm, 2 µm to 8 µm, or 4 µm to 6 µm), as measured using an inductively coupled approach or a similar particle size analyzer on a CoulterCounter Multisize.

[0085] Poly(alkylsilsesquioxane) beads can be formed from the hydrolysis and precipitation of the corresponding silane monomers. The molecular weight of the poly(alkylsilsesquioxane) beads can be 2000 g / mol, 3000 g / mol, 4000 g / mol to 6000 g / mol, 8000 g / mol, 10,000 g / mol, or any range using the foregoing values ​​as endpoints (such as 2000 g / mol to 10000 g / mol, 3000 g / mol to 8000 g / mol, or 4000 g / mol to 6000 g / mol). The molecular weight of the poly(alkylsilsesquioxane) can be measured using GPC or other analytical techniques.

[0086] b. Poly(aryl-alkylsilsesquioxane)

[0087] A representative structure of poly(aryl-alkylsilsesquioxane) is shown in Formula III:

[0088]

[0089] Formula III

[0090] R can be an aryl substituent, such as phenyl; R' can be an alkyl substituent, such as methyl, ethyl, propyl, butyl, octyl, etc.

[0091] Suitable poly(aryl-alkylsilsesquioxane) silicone resins may include POSS-phenylpropyl.

[0092] The structure of poly(aryl-alkyl silsesquioxane) can be composed of about 70% phenyl groups containing silicon atoms and about 30% propyl groups containing silicon atoms. As used herein, poly(aryl-alkyl silsesquioxane) can be in solid, powder, or flake form.

[0093] This powder can be formed from the hydrolysis and precipitation of a mixture of silane monomers. The molecular weight of the poly(aryl-alkyl silsesquioxane) can be 1000 g / mol, 1500 g / mol, 2000 g / mol to 3000 g / mol, 3500 g / mol, 4000 g / mol, or any range using any of the foregoing values ​​as endpoints (such as 1000 g / mol to 4000 g / mol, 1500 g / mol to 3500 g / mol, or 2000 g / mol to 3000 g / mol).

[0094] C. Solvent

[0095] The coating composition may contain one or more solvents. Suitable solvents include water, alcohols (such as C1-C8 alcohols, including methanol, ethanol, isopropanol and tert-butanol), C2-C8 ketones (including acetone), C2-C20 ethers (including dipropylene glycol methyl ether), and other protic or aprotic solvents, such as dimethyl sulfoxide or N-methylpyrrolidone.

[0096] The solvent may be present in the composition in an amount of 15 wt%, 20 wt%, 25 wt%, 30 wt% to 35 wt%, 40 wt%, 45 wt%, 50 wt%, or any value covered by these endpoints (such as 15 wt% to 50 wt%, 20 wt% to 45 wt%, 25 wt% to 40 wt%, or 30 wt% to 35 wt%), wherein the weight percentage is based on the total weight of the “wet” coating composition.

[0097] D. Additives

[0098] In addition to the components described above, additives may also be present in the coating compositions disclosed herein. These additives may include components for improving stability, suitability, and aesthetics. Additives that may be included in the coating compositions of the present invention may include dispersants, defoamers, thickeners, surface agents, colorants, and pigments.

[0099] The total amount of such additives in the coating composition may include 0% by weight, 5% by weight, 10% to 20% by weight, 30% by weight, 40% by weight, or any other combination of these endpoints (such as 0% to 40% by weight, 5% to 30% by weight, or 10% to 20% by weight), wherein the weight percentage is based on the total weight of the “wet” coating composition.

[0100] After the coating is applied and cured, the additive may be present in the coating composition in a total amount ranging from 0 wt%, 2 wt%, 4 wt% to 6 wt%, 8 wt%, 10 wt%, 15 wt%, or any range including any two of these values ​​as endpoints (such as 0 wt% to 10 wt%, 2 wt% to 8 wt%, or 4 wt% to 6 wt%), wherein the weight percentage is based on the total weight of the “dry” coating composition.

[0101] III. Methods for coating rigid substrates

[0102] The coating compositions disclosed herein can be applied to rigid substrates, such as aluminum alloys or other metal substrates, such as components of solenoids, scroll components of scroll compressors, fasteners, nuts, and bolts.

[0103] A. Applying coating

[0104] To apply the disclosed coating composition, the coating composition can be deposited onto a metal substrate by a variety of methods. Application methods may include spraying, dipping, air knife, knife roller, pad printing, screen printing, dip spinning, rack spinning, roller spraying, and electrostatic spraying.

[0105] i. Spraying

[0106] Spraying is another method of applying the coating composition of this application. Spraying involves depositing the coating composition onto a substrate using a spray of coating composition particles or droplets. The substrate may be exposed to the spray of the coating composition from below or otherwise for a predetermined amount of time to deposit the desired amount of coating composition.

[0107] ii. Dipping

[0108] To coat a metal substrate using a dip-coating process, the metal substrate is immersed in a reservoir of the coating composition. The coated substrate is then removed from the reservoir and left to cure.

[0109] iii. Air knife

[0110] Air knife coating is a process of applying a predetermined amount of coating composition to a substrate. The process involves placing the substrate on a series of rollers that move the substrate beneath a mechanism for depositing the coating composition, such as a reservoir that drips the coating composition onto the substrate. Excess coating composition may deposit onto the substrate. To remove excess coating, the coated substrate is passed under an air jet that blows away the excess coating. The positioning angle of the air jet relative to the substrate and the air velocity are calculated such that a predetermined amount of coating composition remains on the substrate. The coating compositions disclosed herein can be applied to metallic substrates using air knife coating.

[0111] iv. Knife roller

[0112] Another process for applying the coating composition of this disclosure to a metal substrate is blade-roll or gap coating. This process involves placing the substrate on a series of rollers that pass beneath the mechanism for depositing the coating composition, similar to the air-knife process described above. The amount of coating composition deposited may exceed the amount required to coat the substrate. To remove excess coating, the coated substrate is passed through a gap created between the substrate and a blade positioned above it. The blade is pre-positioned to scrape away excess coating and leave only the desired amount of coating on the substrate as it passes through the gap.

[0113] B. Curing

[0114] Once the coating composition has been applied to the metal substrate, the coating is cured or dried at a temperature of 170°C, 200°C, 210°C to 220°C, 230°C, 240°C, or any other combination of these endpoints (such as 170°C to 240°C, 200°C to 230°C, or 210°C to 220°C). The coating composition may be cured at the aforementioned temperature for 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, or any other combination of these endpoints (such as 20 minutes to 45 minutes, 25 minutes to 40 minutes, or 30 minutes to 35 minutes).

[0115] IV. Coating Characteristics

[0116] The coating compositions disclosed herein exhibit a variety of properties, including increased abrasion resistance, a low coefficient of friction, and freedom from fluoropolymers.

[0117] A. Wear resistance and coefficient of friction

[0118] During use of a substrate (such as the scroll component of a scroll compressor), the coating composition cured onto the substrate may experience wear due to friction experienced by the coated substrate.

[0119] The coating compositions described in this disclosure improve the durability and abrasion resistance of coated metal substrates. This increased durability extends the lifespan and service life of the substrate and reduces the risk of failure.

[0120] B. Coefficient of friction

[0121] The coefficient of friction (CoF) is a measure of the amount of frictional force between two surfaces. A low CoF indicates that less force is required for sliding to occur than is required when the CoF is high. An increase in CoF means an increase in the rate of wear.

[0122] The abrasion resistance of a substrate can be estimated by measuring the CoF of the coated substrate. A coating with a lower CoF will be more abrasion resistant than a coating with a higher CoF.

[0123] C. Free of perfluoroalkyl substances and N-methylpyrrolidone

[0124] Per- and polyfluoroalkyl substances (PFAS) are fluorinated compounds, including perfluoroalkyl acids (PFAA), such as perfluorooctanoic acid (PFOA) and / or perfluorooctane sulfonate (PFOS).

[0125] With increasingly stringent regulations on PFAS (including fluoropolymers), there has been interest in PFAS-free coating compositions. The coating compositions of the present invention may be PFAS-free, wherein the coating composition is substantially, substantially, or completely free of PFAS. "Substantially PFAS-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 1% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the total PFAS content in the coating composition of this disclosure is less than 1 ppm. "Substantially PFAS-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 0.1% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the total PFAS content in the coating composition of this disclosure is less than 0.1 ppm. "Completely PFAS-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 0.01% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the total PFAS content in the coating composition of this disclosure is less than or less than 0.01 ppm.

[0126] N-methylpyrrolidone (NMP) is an organic substance commonly used as a solvent.

[0127] With increasingly stringent regulations on NMP, there has been interest in NMP-free coating compositions. The coating compositions of the present invention may be NMP-free, wherein the coating composition is substantially, substantially, or completely free of NMP. "Substantially NMP-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 1% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the coating composition of this disclosure has a total NMP content of less than 1 ppm. "Substantially NMP-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 0.1% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the coating composition of this disclosure has a total NMP content of less than 0.1 ppm. "Completely NMP-free" means that, based on the total weight of the coating composition, the coating composition of this disclosure contains a total of 0.01% by weight or less of perfluorinated and polyfluorinated alkyl compounds, and / or, based on the total weight of the coating, the coating composition of this disclosure has a total NMP content of less than 0.01 ppm.

[0128] V. Application

[0129] The coating composition can be applied to any rigid substrate. Suitable substrates may include metallic substrates made of aluminum, aluminum alloys, steel, stainless steel, or other metals and alloys. Suitable substrates may further include scroll components of scroll compressors, contact parts of solenoids, fasteners, nuts, bolts, or other metallic substrates. The coating composition can impart increased wear resistance and lubricity during use of the coated substrate.

[0130] A scroll compressor may include two staggered metal scrolls for pumping / compressing liquids and gases. These two staggered scrolls include a stationary scroll and a rotating scroll. The rotating scroll rotates eccentrically within the stationary scroll without rotating, trapping, or pumping / compressing the fluid pocket between the scrolls. Therefore, the mating surfaces of the scrolls, or scroll wraps, engage with each other, ultimately leading to wear during use. A coating composition may be applied and cured onto the surfaces of the scroll wraps of the scroll compressor to increase the wear resistance of the scrolls, thereby increasing the lifespan of the scroll compressor.

[0131] Furthermore, the coating composition can be applied and cured onto the solenoid actuator / plunger. The solenoid is used to convert electrical energy into mechanical work. The solenoid may include a coil, a housing, and a plunger. When current is applied to the solenoid, a magnetic field is formed around the coil, drawing the plunger into the coil. The current can then be turned off to move the plunger back to its starting position. The movement of the plunger during solenoid use can lead to wear and tear. However, solenoid plungers coated with the coating composition experience increased wear resistance, thereby increasing the solenoid's lifespan.

[0132] Examples

[0133] The aspects of this disclosure will be further illustrated with reference to the following examples. It will be apparent to those skilled in the art that many modifications can be made to the materials and methods without departing from the scope of this disclosure.

[0134] The coating composition according to this disclosure was formulated as follows. The coating composition was applied to a rigid substrate and the properties of the coating were tested to obtain the following results.

[0135] Friction Test Method

[0136] The coating composition was tested using the two friction test methods described below.

[0137] Method 1

[0138] The aluminum pins and discs were each pretreated by sandblasting (AIO, 120 mesh). The coating composition was then applied to the pins and discs by manual spraying using an HVLP gravity supply. After coating, the coated pins and discs were first flash-dried at 150°C for 15 minutes, and then cured at 240°C for 40 minutes. The dry film thickness was 15 to 30 micrometers, as determined using electronic measuring instruments.

[0139] Using a Bruker UMT-3 tribometer, wear tests were performed on coated aluminum pins and discs according to ASTM G99 pin and disc wear test at a linear RPM of 4.98 m / s. The number of cycles (or time) reported up to a coefficient of friction greater than 0.5 was recorded. Each test was repeated 2 to 3 times, and the average number of cycles was reported as the mean average.

[0140] Method 2

[0141] The following method is used to test the abrasion resistance of the coating using steel discs and steel balls.

[0142] The steel discs were pretreated by sandblasting (AIO, 120 mesh). The coating composition was then applied to the discs by manual spraying using an HVLP gravity supply. After coating, the coated discs were first flash-dried at 150°C for 15 minutes, and then cured at 240°C for 40 minutes. The dry film thickness was 15 to 30 micrometers, as determined using electronic measuring instruments.

[0143] Then, the ball and the coated disc were tested using a Bruker UMT-3 tribometer according to the ASTM G99 procedure for ball-on-disc wear testing.

[0144] The steel ball has a diameter of 12.7 mm. The arc length is 2 mm, and the frequency is 5 Hz. Tests were conducted until the coefficient of friction was greater than 0.75. Each test was repeated 3 to 4 times, and the average value was reported. The trend of the coefficient of friction and visible track wear were evaluated.

[0145] Method 3

[0146] Clean the steel tray, 2-inch x 2-inch steel panel, and steel pins with isopropanol or acetone. Pre-treat the tray, panel, and pins with sandblasting (120 mesh alumina). Before applying each coating composition, mix the coating compositions on a pneumatic motor and add Solvent 99B (NMP / xylene: 2 / 1) to adjust the viscosity as measured using a Zahn #2 cup. Add Solvent 99B in 2% increments until the coating composition reaches a viscosity of 30 to 45 seconds in the Zahn #2 cup. Then, remix the material for 10 minutes and fill it into the siphon spray container.

[0147] The coating composition is applied to the pins, panels, and trays by manual spraying. After application, the coated pins, panels, and trays are cured at 176°C for 30 minutes. The dry film thickness of each coating is 15 to 20 μm, as determined using an electronic measuring instrument.

[0148] The coated disc, panel, and pin were tested using a Bruker UMT-3 tribometer. The pin indenter had a diameter of 6.35 mm. The wear track radius was 17 mm, and the test load was 34.5 N at a rotational speed of 2800 rpm.

[0149] Tests were conducted between the pin-disc and pin-panel until the coefficient of friction exceeded 0.5 or sparks were generated. Tests were performed at room temperature (20°C) and 150°C. Trends in the coefficient of friction and visible track wear were evaluated.

[0150] Example 1A: Preparation of Coating Compositions

[0151] Comparative PTFE coating composition 1 was prepared according to Table 1 below.

[0152] Use high-shear mixing to combine all components.

[0153] Table 1: Comparative Coating Composition 1 Formulations

[0154]

[0155] The coatings 1 to 4 of the present invention (Inv.) are prepared according to Tables 2 to 5 below.

[0156] All components were combined using high-shear mixing. The lubricant was mixed at 1200 RPM for 45 minutes using a high-speed mixer. The temperature was kept below 40°C during the mixing process to ensure the stability of the PAI resin.

[0157] Table 2: Invention Coating 1 Formulations (1% dry volume carnauba wax)

[0158]

[0159] Table 3: Invention Coating 2 Formulations (5% dry volume carnauba wax)

[0160]

[0161] Table 4: Invention Coating 3 Formulations (8 to 12% dry volume carnauba wax)

[0162]

[0163] Table 5: Invention Coating 4 Formulations (20% dry volume carnauba wax)

[0164]

[0165] Example 1B: Testing Coating Compositions Using Method 1

[0166] Each of the coatings 1 to 4 of the present invention and the comparative coating 1 was applied to a substrate using method 1 as described above. The results are as follows: Figure 1 and Figure 2 As shown. Figure 1 and Figure 2 As shown, coatings 2, 3, and 4 of the present invention exhibit improved properties compared to comparative coating 1. Coating 2 of the present invention shows a lower CoF compared to the comparative coating. Meanwhile, as... Figure 2 As shown, coatings 3 and 4 of the present invention exhibit significantly lower CoF compared to the comparative coatings.

[0167] Example 2A: Preparation of Coating Compositions

[0168] Comparative PTFE coating composition 2 was prepared according to Table 6 below.

[0169] Use high-shear mixing to combine all components. Mix the lubricant at 1200 RPM for 45 minutes using a high-speed mixer.

[0170] Table 6: Comparative Coating Composition 2 Formulations

[0171]

[0172] The coating 5 of this invention (Inv.) is prepared according to Table 7 below.

[0173] All components were combined using a high-speed mixer at 1200 RPM for 45 minutes. Mechanical grinding was not performed. The temperature was kept below 40°C during the combination process to ensure the stability of the PAI resin.

[0174] Table 7: Invention Coating 5 Formulations (8 to 12 dry volume carnauba wax with NEP)

[0175]

[0176] Example 2B: Testing Coating Compositions Using Method 2

[0177] The comparative coating 2 and the coatings 3 and 5 of the present invention were applied to the substrate using method 1 as described above. The results are as follows: Figure 3 As shown. Figure 3 As shown, coatings 3 and 5 of the present invention exhibit improved properties superior to comparative coating 2. Both coatings 3 and 5 of the present invention have lower CoF compared to comparative coating 2.

[0178] Specific examples of the invention have been described above for illustrative purposes, but it will be apparent to those skilled in the art that many detailed changes may be made to the invention without departing from the invention as defined in the appended claims. Therefore, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Furthermore, this application is intended to cover any such departures from this disclosure within the known or conventional practice in the field to which this disclosure pertains, and which fall within the limitations of the appended claims.

[0179] Example 3A: Preparation of Coating Compositions

[0180] Comparative PTFE coating composition 1 was prepared according to Tables 8 to 10 below.

[0181] Use high-shear mixing to combine all components.

[0182] Table 8: Comparative Coating Composition 3 Formulations

[0183]

[0184] The coating compositions 6 to 20 of the present invention (Inv.) are prepared according to Tables 11 to 25 below.

[0185] All components were combined and mixed using high-shear mixing in air. The temperature during the mixing process was kept below 40°C to ensure the stability of the PAI resin.

[0186] Table 11: Invention Coating 6 Formulations

[0187]

[0188] Table 12: Invention Coating 7 Formulations

[0189]

[0190] Table 13: Invention Coating 8 Formulations

[0191]

[0192] Table 14: Invention Coating 9 Formulations

[0193]

[0194] Table 15: Invention Coating 10 Formulations

[0195]

[0196] Table 16: Invention Coating 11 Formulations

[0197]

[0198] Table 17: Invention Coating 12 Formulations

[0199]

[0200] Table 18: Invention Coating 13 Formulations

[0201]

[0202] Table 19: Invention Coating 14 Formulations

[0203]

[0204] Table 20: Invention Coating 15 Formulations

[0205]

[0206] Table 21: Invention Coating 16 Formulations

[0207]

[0208] Table 22: Invention Coating 17 Formulations

[0209]

[0210] Table 23: Invention Coating 18 Formulations

[0211]

[0212] Table 24: Invention Coating 19 Formulations

[0213]

[0214] Table 25: Invention Coating 20 Formulations

[0215]

[0216] Table 26: Invention Coating 21 Formulations

[0217]

[0218] Table 27: Invention Coating 22 Formulations

[0219]

[0220] Example 3B: Testing Coating Compositions Using Method 3

[0221] Comparative coatings 3 to 5 and coatings 6 to 20 of the present invention were applied to a substrate using method 3 as described above. The results are shown in Tables 26, 27, and 28. Figures 4 to 6 As shown.

[0222] Table 28: Test Results for Comparative Example 3 and Inventive Examples 6 to 11

[0223]

[0224] Table 29: Test Results for Comparative Example 3 and Inventive Examples 12 to 15

[0225]

[0226] Table 30: Test Results for Comparative Example 3 and Inventive Examples 16 to 20

[0227]

[0228] Table 31: Test Results for Inventive Examples 21 to 22

[0229]

[0230] The results are as follows Figure 4 As shown, coatings 7, 10, and 11 of the present invention exhibit improved properties superior to comparative coating 3. Coating 11 of the present invention exhibits a significantly lower CoF compared to comparative coating 3.

[0231] exist Figure 5 In comparison with the comparative coating 3, the coatings 13, 12 and 15 of the present invention all exhibit significantly lower CoF.

[0232] And ultimately, in Figure 6 In comparison with comparative coating 5, coatings 17, 19, and 20 of the present invention all exhibit lower CoF. Coating 19 of the present invention shows a significant improvement in properties compared to comparative coating 3.

[0233] Prophetic Example 4: Coating Composition with Epoxy Adhesive Resin

[0234] The coatings 6 to 20 of the present invention were prepared using the same formulations listed in Example 3A, except that epoxy resin was used as the adhesive resin instead of PAI.

[0235] Method 3 was used to test the coating of the present invention using epoxy adhesive resin, and a comparative coating 3 was also tested. The results showed that the coating of the present invention with epoxy adhesive resin exhibited improved properties superior to the comparative coating 3.

[0236] Prophetic Example 5: Coating Composition with Silicone-Polyester Adhesive Resin

[0237] The coatings 6 to 20 of the present invention were prepared using the same formulations listed in Example 3A, except that an organosilicon polyester resin was used as the adhesive resin instead of PAI.

[0238] Method 3 was used to test the coating of the present invention using the silicone polyester adhesive resin, and a comparative coating 3 was also tested. The results showed that the coating of the present invention having the silicone polyester adhesive resin had improved properties superior to those of the comparative coating 3.

[0239] Prophetic Example 6: Coating Composition with Polyurethane Adhesive Resin

[0240] The coatings 6 to 20 of the present invention were prepared using the same formulations listed in Example 3A, except that polyurethane was used as the adhesive resin instead of PAI.

[0241] Method 3 was used to test the coating of the present invention using a polyurethane adhesive resin, and a comparative coating 3 was also tested. The results showed that the coating of the present invention using a polyurethane adhesive resin exhibited improved properties superior to those of the comparative coating 3.

Claims

1. A coating composition for rigid substrates, the coating composition comprising: a binder resin; a lubricating component comprising a wax; and a solvent.

2. The coating composition of claim 1, wherein the binder resin is selected from the group consisting of polyamideimides, epoxy resins, silicone polyesters, and polyurethane resins.

3. The coating composition of claim 1 or claim 2, wherein the lubricating component further comprises a silicone resin.

4. The coating composition of claim 3, wherein the silicone resin is selected from the group consisting of poly(aryl-alkylsilsesquioxane) and poly(alkylsilsesquioxane).

5. The coating composition of any one of claims 1 to 4, wherein the wax has a melting point of 70 °C to 140 °C as determined by differential scanning calorimetry (DSC) according to ASTM E794-06 (2018).

6. The coating composition of any one of claims 1 to 5, wherein the wax is at least one of carnauba wax, polyethylene wax, polypropylene wax, polyamide wax, and Fischer-Tropsch wax.

7. The coating composition of any one of claims 1 to 6, wherein the binder resin comprises 20 to 80 weight percent of the coating composition based on the total wet weight of the coating composition.

8. The coating composition of any one of claims 1 to 7, wherein the binder resin comprises 35 to 78 weight percent of the coating composition based on the total wet weight of the coating composition.

9. The coating composition of any one of claims 1 to 8, wherein the wax comprises 0.05 to 10 weight percent of the coating composition based on the total wet weight of the coating composition.

10. The coating composition of any one of claims 1 to 9, wherein the silicone resin comprises 1 to 10 weight percent of the coating composition based on the total wet weight of the coating composition.

11. The coating composition of any one of claims 1 to 10, wherein the wax comprises wax particles having an average particle size (D50) of less than 12 microns as determined by dynamic light scattering ISO 13320-1.

12. The coating composition of any one of claims 1 to 11, comprising a total amount of 1 ppm or less of perfluoroalkyl substances (PFAS) based on the total weight of the coating composition.

13. The coating composition of any one of claims 1 to 12, comprising a total amount of 1 ppm or less of N-methylpyrrolidone (NMP) based on the total weight of the coating composition.

14. A method of coating a rigid substrate, the method comprising: applying the coating composition of any one of claims 1 to 13 to the rigid substrate; and curing the coating composition at a temperature of 170 to 240 °C.

15. A coated rigid substrate, the coated rigid substrate comprising: a rigid substrate; and a coating on the rigid substrate, the coating comprising: a binder resin; and a lubricating component comprising a wax.

16. The coated rigid substrate of claim 15, wherein the adhesive resin is selected from the group consisting of polyamideimides, epoxy resins, silicone polyesters, and polyurethane resins.

17. The coated rigid substrate of claim 15 or claim 16, wherein the lubricious component further comprises a silicone resin.

18. The coated rigid substrate of claim 17, wherein the silicone resin is selected from the group consisting of poly(aryl-alkylsilsesquioxane) and poly(alkylsilsesquioxane).

19. The coated rigid substrate of any one of claims 15 to 18, wherein the wax has a melting point of 70 °C to 140 °C as determined by ASTM D87.

20. The coated rigid substrate of any one of claims 15 to 19, wherein the wax is at least one of carnauba wax, polyethylene wax, polypropylene wax, polyamide wax, and Fischer-Tropsch wax.

21. The coated rigid substrate of any one of claims 15 to 20, wherein the adhesive resin comprises 35 to 98 weight percent of the coating composition based on the total dry weight of the coating composition.

22. The coated rigid substrate of any one of claims 15 to 21, wherein the adhesive resin comprises 40 to 98 volume percent of the coating composition based on the total dry volume of the coating composition.

23. The coated rigid substrate of any one of claims 15 to 22, wherein the wax comprises 0.1 to 35 weight percent of the coating composition based on the total dry weight of the coating composition.

24. The coated rigid substrate of any one of claims 15 to 23, wherein the wax comprises 0.5 to 45 volume percent of the coating composition based on the total dry volume of the coating composition.

25. The coated rigid substrate of claim 17 or claim 18, wherein the silicone resin comprises 15 to 40 weight percent of the coating composition based on the total dry weight of the coating composition.

26. The coated rigid substrate of claim 17 or claim 18, wherein the silicone resin comprises 10 to 45 volume percent of the coating composition based on the total dry volume of the coating composition.

27. The coated rigid substrate of any one of claims 15 to 26, wherein the substrate is a metallic material including aluminum, steel, other metal alloys, or combinations of the foregoing.

28. The coated rigid substrate of any one of claims 15 to 27, wherein the substrate is a fixed or orbiting scroll component of a scroll compressor.

29. The coated rigid substrate of any one of claims 15 to 28, wherein the substrate is a screw tube plunger.

30. The coated rigid substrate of any one of claims 15 to 29, wherein the substrate is one of a fastener, a nut, and a bolt.

31. The coated rigid substrate according to any one of claims 15 to 30, wherein the wax comprises wax particles having an average particle size (D50) of less than 12 microns as determined by dynamic light scattering ISO 13320-1.

32. The coated rigid substrate according to any one of claims 15 to 31, comprising a total amount of 1 ppm or less of perfluoroalkyl substances (PFAS), based on the total weight of the coating composition.

33. The coated rigid substrate according to any one of claims 15 to 32, comprising a total amount of 1 ppm or less of N-methylpyrrolidone (NMP), based on the total weight of the coating composition.

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