Low Coefficient of Friction Coating for Metallic Surfaces
Disclosed herein is an article or device such as surgical devices, needles such as surgical needles, razors, cutting/slicing devices containing a metallic surface, a primer layer disposed on the metallic surface, and a top coat disposed on the primer layer, wherein the primer layer is formed from a primer composition containing a silanol-containing organopolysiloxane resin and a crosslinking agent selected from the group consisting of alkyl silicates, boric acid, borates, acetoxysilanes, ketoximesilanes, and combinations thereof, and wherein the top coat is formed from a top coat composition containing an alkenyl functional polyorganosiloxane, an organohydrogensiloxane, and a hydrosilylation catalyst.
1 . An article comprising a metallic surface, a primer layer disposed on said metallic surface, and a top coat disposed on said primer layer, wherein said primer layer is formed from a primer composition containing a silanol-containing organopolysiloxane resin and a crosslinking agent selected from the group consisting of alkyl silicates, boric acid, borates, acetoxysilanes, ketoximesilanes, and combinations thereof, and wherein said top coat is formed from a top coat composition containing an alkenyl functional polyorganosiloxane, an organohydrogensiloxane, and a hydrosilylation catalyst.
2 . The article of claim 1 wherein said metallic surface comprises a metal selected from the group consisting of stainless steel, tungsten, nickel, cobalt, molybdenum, tin, vanadium, titanium, aluminum, iron, copper, zinc, silver, lead, and combinations thereof.
3 . The article of claim 2 wherein said metallic surface is made of stainless steel.
4 . The article of claim 2 wherein said metallic surface contains tungsten.
5 . The article of claim 1 wherein said silanol-containing organopolysiloxane resin in the primer composition is represented by the following formula:
M a D b T c Q d , (Formula I)
wherein M=R 1 R 2 R 3 SiO 1/2 ; D=R 4 R 5 SiO 2/2 ; T=R 6 SiO 3/2 ; and Q=SiO 4/2 , wherein the subscripts a, b, c, and d are zero or positive and are chosen so that the resin has a viscosity, based on a 50 wt % solids solution in an aromatic solvent, varying between about 5 centistokes and 10,000 centistokes, and where each R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 is independently selected from the group of hydrogen, hydroxyl, C1 to C60 monovalent alkyl radicals; C1 to C60 monovalent halo-alkyl radicals; C1 to C60 monovalent aryl radicals; C1 to C60 monovalent alkylaryl radicals; and C1 to C60 monovalent halo-alkylaryl radicals, subject to the limitation that at least one of R 1 , R 2 , and R 3 is hydroxyl.
6 . The article of claim 5 wherein said silanol-containing organopolysiloxane is represented by Formula (II):
D e T f (Formula II)
wherein D=R 7 R 8 SiO 2/2 ; T=R 9 SiO 3/2 , wherein each R 7 , R 8 and R 9 is independently aklyl, hydroxyl, alkoxy or acyloxy, provided that at least one of R 7 , R 8 and R 9 per molecule is hydroxyl, e is from about 160 to about 450, and f is from about 15 to about 50.
7 . The article of claim 1 wherein said alkyl silicate in said primer composition is a condensate obtained by partially hydrolyzing at least one tetraalkyl silicate represented by the following formula: Si(OR 10 )(OR 11 )(OR 12 )(OR 13 ), wherein each occurrence of R 10 , R 11 , R 12 and R 13 , represents an alkyl group containing 1 to 4 carbon atoms.
8 . The article of claim 7 wherein said alkyl silicate is a condensate of tetraethyl silicate.
9 . The article of claim 1 wherein said primer composition additionally contains a condensation catalyst.
10 . The article of claim 9 wherein said catalyst is ferric chloride.
11 . The article of claim 1 wherein said alkenyl functional organopolysiloxane is a vinyl chain-stopped polysiloxane having the general formula:
wherein R 14 is a monovalent hydrocarbon radical free of unsaturation, R 15 is a hydrocarbon radical having alkenyl unsaturation, x is from 0 to 6300, y is from 0 to 250, provided that the sum of x+y is at least 80.
12 . The article of claim 11 , wherein R 14 is methyl, and R 15 is vinyl or vinyl ether.
13 . The article of claim 1 wherein the organohydrogensiloxane is a substantially linear hydrogen siloxane having a formula selected from the group consisting of
MD r D H s M
MD H r M
MD r D H s M H
M H D r D H s M H , and
M H D r M H
where M is defined as R 16 3 SiO 1/2
M H is defined as H g R 16 3-g SiO 1/2
D=R16R 16 SiO 2/2
D H =R 16 HSiO 2/2
where each R 16 is independently a monovalent hydrocarbon of from 1 to 40 carbon atoms, the subscripts r and s may be zero or positive wherein the sum of r and s ranges from about 10 to about 100, with the proviso that the sum of r and g is at least 2.
14 . The article of claim 13 wherein the organohydrogensiloxane is MD H k M, where f is greater than 0 and less than about 100, M and D H are as defined in claim 12 .
15 . The article of claim 1 wherein said hydrosilylation catalyst is a platinum based complex.
16 . The article of claim 1 wherein said top coat composition contains a solvent.
17 . The article of claim 1 wherein the article is a surgical needle.
18 . The article of claim 1 wherein the article is a surgical device.
19 . A method for making an article or a device having a coated metallic surface comprising the steps of: (1) providing an article or a device having at least one metallic surface; (2) providing a primer composition and a coating composition according to claim 1 ; (3) contacting said metallic surface with said primer composition to form a primer layer; (4) contacting said primer layer with said top coat composition to form a top coat; (5) curing said primer layer and said top coat thereby making said article or device.
20 . The method of claim 19 wherein the step of contacting the metallic surface with the primer composition is selected from the group consisting of dipping, spraying, brushing or wiping.
21 . The method of claim 19 wherein said method additionally comprises a step of drying the primer composition to form a primer layer.
22 . The method of claim 19 wherein said primer layer and said top coat are cured at a temperature of from 80 to 300° C. for about one second to twenty minutes.
23 . An article or device prepared by the method of claim 19 .