BACKGROUND OF THE INVENTION Lubricating coatings are thin film coatings that increase the lifetime of the substrate by reducing damage caused by wear. Such solid coatings are required in applications where components are subjected to harsh environmental conditions such as high temperatures and intense radiation. Lubricating coatings find utility in precision applications which include but are not limited to machine tools (e. g. drill bits, end mills, etc.), close tolerance gimbals, bearings, shafts, and gears.

Additionally, lubricating coatings are applied to wood surfaces which are subjected to friction. The use of lubricating coatings reduce the amount of friction between moving parts resulting in decreased heat production, stress, surface deformation and fatigue forces.

Many methods exist for depositing the solid coating onto the substrate. For example, the coatings have been rubbed, bonded, thermally sprayed, and laser deposited onto the substrate. Additionally, sputter deposition has been commonly used to coat substrates.

By utilizing any of these methods, film quality is limited and environmental concerns exist. For example, sputter deposition leads to contamination by background gases. Contamination can compromise film integrity any limit control of the film properties. Additionally, these methods typically require the use of organic solvents that contain a significant amount of volatile organic compounds (VOCs). These VOCs escape into the atmosphere while the composition dries. Such solvent based systems are undesirable because of the

hazards and expenses associated with VOCs. The hazards include water and air pollution and the expenses include the cost of complying with strict government regulation on solvent emission levels.

In contrast, UV curable compositions contain reactive monomers instead of solvents; thus eliminating the detrimental effects of VOCs. UV compositions are cured through rapid photo-induced polymerizations without the use of solvents which emit VOCs. Since the UV curing process is essentially solvent free, the necessity for time consuming and expensive pollution abatement procedures is greatly reduced.

Additionally, UV curable lubricating coatings offer several other benefits. First, faster cure times offer substantial economic benefits. Furthermore, heat sensitive materials can be safely coated and cured with UV light without thermal degradation of heat sensitive substrates. Additionally, UV light is a relatively low cost source of energy due to its widespread availability.

Although UV curable lubricant coatings are superior to their counterparts, there are still disadvantages inherent in UV curable coatings. Since UV curable coatings require compositions which have high molecular weight and viscosity, it is difficult to apply the composition through spraying and brushing.

Additionally, many UV curable lubricant coatings require compositions that are prone to dispersion and instability. By using these compositions, the curing results in an uneven and blemished coating.

Accordingly, there exists a need to provide environmentally safe UV curable lubricant coatings with enhance physical properties for use on substrates subjected to harsh environmental conditions. Additionally, there is a need to provide a method of applying the coatings which furthers the goal of improved performance.

SUMMARY OF INVENTION It is an object of the present invention to provide an improved composition that upon curing by ultraviolet light produces a coating that is lubricating.

It is another object of the present invention to provide an improved composition that upon curing by ultraviolet light produce a textured coating that is lubricating.

It is another object of the present invention to provide an improved composition that can be applied by spraying, screen printing, dipping, and brushing.

The present invention discloses an ultraviolet light curable lubricating composition and method for making such a composition that may be used to produce a lubricating layer. The disclosed composition does not contain any significant amount of volatile organic solvents that do not become incorporated in the lubricating layer after curing. Specifically, the lubricating composition contains 5 % or less volatile organic solvents by weight.

In accordance with one aspect of the invention, an ultraviolet light curable lubricating composition is provided. The lubricating composition comprises a mixture of one or more aliphatic acrylated oligomers, wherein the aliphatic acrylated oligomer mixture is present in an amount of about 10% to 45% of the lubricating composition. All percentages of the lubricating composition as expressed in this document refer to the weight percentage of the stated component to the total weight of the lubricating composition in its fluid state at standard temperature and pressure.

The lubricating composition preferably further comprises an acrylated epoxy oligomer in an amount of about 2% to 8%, an isobornyl acrylate monomer in an amount of about 15% to 60% of the lubricating composition, a photoinitiator in an amount of about 2 % to 8 % of the lubricating composition, a flowing promoting

agent in an amount of 0.0% to 8%, and a teflon composition in an amount of about 15% to 40% of the lubricating composition.

In accordance with yet another aspect of the invention, a method is provided for depositing a lubricating coating on a substrate. The method comprises a first step of applying to the substrate a lubricating fluid-phase composition ("lubricating composition"). The lubricating composition comprises the composition described above.

The method also includes a second step of illuminating the lubricating composition on the substrate with an ultraviolet light to cause the lubricating composition to cure into the lubricating coating.

In accordance with this method, the lubricating composition can be selectively deposited on the substrate at specific locations where lubricating plating is desired. It need not be applied to the entire substrate.

BEST MODE FOR CARRYING OUT THE INVENTION Lubricating Compositions Reference will now be made in detail to presently preferred compositions or embodiments and methods of the invention, which constitute the best modes of practicing the invention presently known to the inventor.

In accordance with one aspect of the invention, a presently preferred ultraviolet light curable lubricating composition ("lubricating composition") is provided. In this preferred embodiment, the lubricating composition includes a mixture of aliphatic acrylated oligomers. The aliphatic acrylated oligomer mixture is present in an amount of about 10 % to 45 % of the lubricating composition. If the lubricating composition is applied by screen printing, the aliphatic acrylated oligomer mixture is more preferably present in an amount of about 25 % to 40 %, and most preferably about 34 %. If the lubricating composition is applied by spray

techniques, the aliphatic acrylated oligomer mixture is more preferably present in an amount of about 11% to 21%, and most preferably about 16%. The aliphatic acrylated oligomer preferably comprises one or more urethane oligomers. Suitable aliphatic acrylated oligomers include Radcure Ebecryl 244 (aliphatic urethane diacrylate diluted 10% with 1,6-hexanediol diacrylate), Ebecryl 264 (aliphatic urethane triacrylate diluted 15 % with 1,6-hexanediol diacrylate) and Ebecryl 284 (aliphatic urethane diacrylate diluted 12 % by weight with 1,6-hexanediol diacrylate) urethanes, commercially available from Radcure UCB Corp. of Smyrna, Georgia; Sartomer CN-961E75 (aliphatic urethane diacrylate blended with 25% ethoxylated trimethylol propane triacylate), CN-961H81 (aliphatic urethane diacrylate blended with 19 % 2 (2-ethoxyethoxy) ethyl acrylate), CN-963A80 (aliphatic urethane diacrylate blended with 20% tripropylene glycol diacrylate), CN-964 (aliphatic urethane diacrylate), CN-966A80 (aliphatic urethane diacrylate blended with 20% tripropylene glycol diacrylate), CN-982A75 (aliphatic urethane diacrylate blended with 25 % tripropylene glycol diacrylate) and CN-983 (aliphatic urethane diacrylate), commercially available from Sartomer Corp. of Exton, Pennsylvania; TAB FAIRAD 8010,8179,8205,8210,8216,8264, M-E-15, UVU-316, commercially available from TAB Chemicals of Chicago, Illinois; and Echo Resin ALU-303, commercially available from Echo Resins of Versaille, Missouri; and Genomer 4652, commercially available from Rahn Radiation Curing of Aurora, IL. The preferred aliphatic acrylated oligomers include Ebecryl 264 and Ebecryl 284. Ebecryl 264 is an aliphatic urethane triacrylate supplied as an 85 % solution in hexandiol diacrylate.

Ebecryl 284 is aliphatic urethane diacrylate of 1200 molecular weight diluted 10 % with 1,6-hexanediol diacrylate. Combinations of these materials may also be employed herein.

This preferred lubricating composition further includes an acrylated epoxy oligomer. The acrylated epoxy oligomer is present in an amount of about 2 % to 8%. If the lubricating composition is applied by screen printing, the acrylated epoxy oligomer is more preferably present in an amount of about 3 % to 6 %, and most preferably about 5 %. If the lubricating composition is applied by spraying, the acrylated epoxy oligomer is more preferably present in an amount of about 3 % to 6%, and most preferably about 4%. Suitable acrylated epoxy oligomers include

Radcure Ebecryl 3603 (novolac epoxy acrylate diluted 20 % with tripropylene glycol diacrylate), commercially available from Radcure UCB Corp.; Sartomer CN-120 (difunctional bisphenol based epoxy acrylate) and CN-124 (difunctional bisphenol based epoxy acrylate), commercially available from Sartomer Corp.; and Echo Resin TME 9310 and 9345, commercially available from Echo Resins. The preferred acrylated epoxy oligomer is Ebecryl 3603, which tri-functional acrylated epoxy novolac. Combinations of these materials may also be employed herein.

The preferred lubricating composition also includes an isobornyl acrylate monomer in an amount of about 15 % to 60 %. If the lubricating composition is applied by screen printing, the isobornyl acrylate monomer is more preferably present in an amount of about 15% to 30%, and most preferably about 23 %. If the lubricating composition is applied by spraying, the isobornyl acrylate monomer is more preferably present in an amount of about 40% to 60%, and most preferably about 50%. Suitable isobornyl acrylate monomers include Sartomer SR- 423 (isobornyl methacrylate): and SR-506 (isobornyl acrylate) : available from Sartomer Corp.; Radcure IBOA (isobornyl acrylate), commercially available from Radcure Corp.; IBOA and IBOMA, commercially available from CPS

Chemical; and Genomer 1121, commercially available from Rahn Radiation Curing.

The preferred isobornyl acrylate monomers is Radcure IBOA, commercially available from Radcure Corp. Combinations of these materials may also be employed herein.

This preferred lubricating composition also includes a photoinitiator in an amount of about 2 % to 8 % of the lubricating composition. If the lubricating composition is applied by screen printing, the photoinitiator is more preferably present in an amount of about 3 % to 7 %, and most preferably about 5 %. If the lubricating composition is applied by spraying, the photoinitiator is more preferably present in an amount of about 3 % to 7 %, and most preferably about 5 %. Suitable photoinitiators include Irgacure 184 (1-hydroxycyclohexyl phenyl ketone); Irgacure 907 (2-methyl-l- [4- (methylthio) phenyl]-2-morpholino propan-1-one) ; Irgacure 369 (2-benzyl-2-N, N-dimethylamino-1- (4-morpholinophenyl)-1-butanone) ; Irgacure 500 (the combination of 50% 1-hydroxy cyclohexyl phenyl ketone and 50% benzophenone); Irgacure 651 (2,2-dimethoxy-2-phenyl acetophenone); Irgacure 1700 (the combination of 25 % bis (2,6-dimethoxybenzoyl-2,4-, 4-trimethyl pentyl phosphine oxide and 75% 2-hydroxy-2-methyl-1-phenyl-propan-1-one) ; DAROCUR 1173 (2-hydroxy-2-methyl-lphenyl-1-propane) and DAROCUR 4265 (the combination of 50% 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide and 50% 2- hydroxy 2-methyl-1-phenyl-propan-1-one), available commercially from Ciba-Geigy Corp., Tarrytown, N. Y.; CYRACURE UVI-6974 (mixed triaryl sulfonium hexafluoroantimonate salts) and CYRACURE UVI-6990 (mixed triaryl sulfonium hexafluorophosphate salts) available commercially from Union Carbide Chemicals and Plastics Co. Inc., Danbury, Conn.; and Genocure CQ, Genocure BOK, and Genocure M. F., commercially available from Rahn Radiation Curing. The preferred photoinitiator is Irgacure 1700 commercially available from Ciba-Geigy of Tarrytown, New York. Combinations of these materials may also be employed herein.

The composition still further includes a flow promoting agent in an amount of about 0.0% to 8%. If the lubricating composition is applied by screen printing, the flow promoting is more preferably present in an amount of about 1 %

to 7 %, and most preferably about 3 %. If the lubricating composition is applied by spraying, the flow promoting agent is more preferably present in an amount of about 3 % to 7 %, and most preferably about 4 %. Suitable flow promoting agents include Genorad 17, commercially available from Rahn Radiation Curing ; and Modaflow, commercially available from Monsanto Chemical Co., St. Louis, Missouri. The preferred flow promoting agent is Modaflow which is an ethyl acrylate and 2- ethylhexyl acrylate copolymer that improves the flow of the composition.

Combinations of these materials may also be employed herein.

The preferred composition still further includes a teflon composition in an amount of about 15% to 40%. If the lubricating composition is applied by screen printing, the teflon composition is more preferably present in an amount of about 25 % to 35 %, and most preferably about 31 %. If the lubricating composition is applied by spraying, the teflon composition is more preferably present in an amount of about 15% to 25%, and most preferably about 21%. Suitable Teflons include Zonyl MP 1000 Fluoroadditive, Zonyl MP 1100 Fluoroadditive, and Zonyl MP 1300 Fluoroadditive, commercially available from Du Pont Company, Wilmington, Delaware.

To illustrate, the following example sets forth a presently preferred lubricating composition according to this aspect of the invention.

Example 1 This example provides a preferred lubricating composition according to the invention that can be applied to a substrate by screen printing techniques. The lubricating composition was made from the following components: Component Approximate Weight% Ebecryl26416. 9 Ebecryl 284 16. 9

Component Approximate Weight % IBOA 22. 1 Irgacure 1700 5. 0 Ebecryl 3603 4. 5 Modaflow 3. 3 MP 1300 31. 3 Total 100.

In this example the IBOA and Irgacure 1700 are mixed in a pan with a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the next step, the Ebecryl 264, the Ebecryl 284, the Ebecryl 3603, and Modaflow are introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm. In the final step, the MP1300 is introduced into the pan and mixed for 1 to 2 minutes at a speed of 5000 rpm. The temperature during mixing is monitored. The mixing is temporarily suspended if the temperature exceed 100°F.

Example 2 This example provides a preferred lubricating composition according to the invention that can be applied to a substrate by spraying. The lubricating composition was made from the following components: Component Approximate Weight % Ebecryl 264 8. 0 Ebecryl 284 8. 0 IBOA 50. 0 Irgacure 1700 5. 0 Ebecryl 3603 4. 0 Modaflow 4. 0 MP 1300 21.1 Component Approximate Weight % Total 100. 00

In this example the IBOA and Irgacure 1700 are mixed in a pan with a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the next step, the Ebecryl 264, the Ebecryl 284, the Ebecryl 3603, and Modaflow are introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm. In the final step, the MP1300 is introduced into the pan and mixed for 1 to 2 minutes at a speed of 5000 rpm. The temperature during mixing is monitored. The mixing is temporarily suspended if the temperature exceed 100°F.

Example 3 This example provides a preferred lubricating composition according to the invention that can be applied to a substrate in piston applications. The lubricating composition was made from the following components: Component Approximate Weight % Ebecryl 264 7. 3 Ebecryl 284 7. 3 IBOA 45. 5 Irgacure 1700 4. 5 Ebecryl 3603 3. 6 Modaflow 3. 6 MP 1300 19. 1 Pthalo Blue Total 100. 00 In this example the IBOA and Irgacure 1700 are mixed in a pan with a propeller blade mixer for 30 seconds at a speed of 500 to 1000 rpm. In the next step, the Ebecryl 264, the Ebecryl 284, the Ebecryl 3603, and Modaflow are

introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm. In the next step, the MP1300 is introduced into the pan and mixed for 1 to 2 minutes at a speed of 2000 rpm. In the final step, the Pthalo Blue is added and mixed for 1 to 2 minutes at a speed of 2000 rpm. In this example, the Pthalo Blue is merely an additive that provides a blue color to the composition. The temperature during mixing is monitored. The mixing is temporarily suspended if the temperature exceed 100°F.

Method for Depositing a Coating on a Substrate In accordance with still another aspect of the invention, a method is provided for depositing a lubricating coating on a suitable substrate. The method comprises a first step of applying a lubricating fluid-phase composition ("lubricating composition") to the substrate.

The lubricating composition comprises the compositions described above. The preferred lubricating compositions according to this method are those described herein, for example, including the compositions described in examples 1- 3.

The lubricating composition may be applied to the substrate using a number of different techniques. The lubricating composition may be applied, for example, by direct brush application, dipping, or it may be sprayed onto the substrate surface. It also may be applied using a screen printing technique. In such screen printing technique, a"screen"as the term is used in the screen printing industry is used to regulate the flow of liquid composition onto the substrate surface.

The lubricating composition typically would be applied to the screen as the latter contacts the substrate. The lubricating composition flows through the silk screen to the substrate, whereupon it adheres to the substrate at the desired film thickness.

Screen printing techniques suitable for this purpose include known techniques, but wherein the process is adjusted in ways known to persons of ordinary skill in the art to accommodate the viscosity, flowability, and other properties of the liquid-phase composition, the substrate and its surface properties, etc. Flexographic techniques,

for example, using pinch rollers to contact the lubricating composition with a rolling substrate, also may be used.

The method includes a second step of illuminating the lubricating fluid-phase composition on the substrate with an ultraviolet light to cause the lubricating fluid-phase composition to cure into the lubricating coating. This illumination may be carried out in any number of ways, provided the ultraviolet light or radiation impinges upon the lubricating composition so that the lubricating composition is caused to polymerize to form the coating, layer, film, etc., and thereby cures.

Curing preferably takes place by free radical polymerization, which is initiated by an ultraviolet radiation source. The photoinitiator preferably comprises a photoinitiator, as described above.

Various ultraviolet light sources may be used, depending on the application. Preferred ultraviolet radiation sources for a number of applications include known ultraviolet lighting equipment with energy intensity settings of, for example, 125 watts, 200 watts, and 300 watts per square inch.

While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.