Claims:We Claim:

1. Hybrid polysiloxane clear and pigmented coating formulation/composition comprising
(i) 40-90 wt. % of resin blend including 2-9% epoxy resin/s, and, siloxane oligomer grafted glycidyl functional acrylic resin, said acrylic resin comprising a reaction product of hydroxyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g and silanol and alkoxy functional organosiloxane resin;
(ii) 5-20 wt. % hardener including aminosilane hardener.
2. Hybrid polysiloxane clear and pigmented coating formulation/composition as claimed in claim 1 as a two component system involving stable flowable resin blend (i) wherein said epoxy resin/s of said resin blend is preferably at least one cycloaliphatic epoxy resin or combinations thereof, said resin blend including siloxane oligomer grafted glycidyl functional acrylic resin comprising silanol and alkoxy functional organosiloxane resin grafted onto base hydroxyl and glycidyl functional acrylic resin enabling said siloxane oligomer grafted glycidyl functional acrylic resin overall having 2-9 % epoxy percent on resin solids, 10-40% silicone % on resin solids, and epoxy equivalent wt. in the range of 300-900 g/ eq. suiting pigmented formulation preferably 500-700 g/ eq., suiting clear formulation; and
wherein said silicone oligomer grafted glycidyl functional acrylic resin comprises hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g stabilized by incorporation of mono-functional alcohol including methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol preferably isobutanol; and
wherein the balance ingredients of said formulation being conventional paint ingredients including solvents.

3. Hybrid polysiloxane clear and pigmented coating formulation/composition as claimed in claims 1 or 2 wherein said siloxane oligomer grafted hydroxyl and glycidyl functional acrylic resin of component (i) is a reaction product of
(a) 60-90 wt.% hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g, and,
(b) 10-40 wt.% of organosiloxane oligomer with methoxy functionality enabling epoxy equivalent wt. in the range of 300-900 g/eq. more preferably 500-700 g/ eq. of said siloxane oligomer grafted base hydroxyl and glycidyl functional acrylic resin.

4. Hybrid polysiloxane clear and pigmented coating formulation/composition as claimed in claims 1-3 wherein said hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g is a polymer of monomers including esters of acrylic/methacrylic acid, hydroxy functional and glycidyl functional acrylate monomers including monomers of 0-10 % Methyl methacrylate, 3-14 % Butyl Acrylate, 0-5 % Butyl Methacrylate, 5-35 % Glycidyl acrylate/Glycidyl Methacrylate (GMA), 0-15 % Hydroxyethyl methacrylate (HEMA), hydroxyl ethyl acrylate 0-15 % (HEA).

5. A process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition comprising the steps of providing
(i) 40-90 wt. % of resin blend including 2-9 % epoxy resin & siloxane oligomer grafted glycidyl functional acrylic resin, said acrylic resin obtained by reacting hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g with silanol and alkoxy functional organosiloxane resin;
(ii) 5-20 wt. % hardener including aminosilane hardener;
(iii) curing the resin blend of (i) with (ii) in the presence of catalyst preferably Dibutyltin dilaurate (DBTDL) and obtaining therefrom clear/pigmented and glossy films with flexibility and adhesion characteristics and retention of gloss.

6. A process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition as claimed in claim 5 wherein said resin blend of step (i) including epoxy resin/s & siloxane oligomer grafted glycidyl functional acrylic resin is obtained based on the following steps of

(a) Radical polymerizing mixture of monomers including esters of acrylic/methacrylic acid, hydroxy functional and glycidyl functional acrylate monomers including monomers of 0-10 % Methyl methacrylate, 3-14 % Butyl Acrylate, 0-5 % Butyl Methacrylate, 5-35 % Glycidyl acrylate/ Glycidyl Methacrylate (GMA), 0-15 % Hydroxyethyl methacrylate (HEMA), hydroxyl ethyl acrylate 0-15 % (HEA) in organic solvents including butyl acetate, cellosolve acetate, xylene as solvents with initiator including TBPB (Tertiary butyl perbenzoate) as initiator in the presence of nitrogen and heating in temperature range of 140-150 deg C wherein said mixture of monomers and initiator are added dropwise over 4 hours by maintaining temperature range of 140-150 deg C followed by carrying out digestion for 3 hours at 140-150 deg C with addition of extra initiator during last hour of digestion and obtaining therefrom both –OH and glycidyl functional acrylic resin having -OH value in the range of 50 to 150 mg KOH/g;
(b) condensation polymerizing –OH and glycidyl functional acrylic resin of step (a) above with silanol and alkoxy/methoxy/ethoxy functional organosiloxane resin involving tetra isopropyl titanate catalyst by starting heating at 60?C followed by adding the mixture of organosiloxane resin in the presence of mono-functional alcohol dropwise to the resin and said catalyst over a period of 30 to 40 minutes while continuing to stir and maintaining temperature at 60-70?C and thereafter gradually heating the contents to 120?C over a period of 1-3 hours at 120 ?C and maintaining temperature while stirring to attain single phase clear droplet indicating reaction termination to obtain methanol/ethanol as by-product and siloxane oligomer grafted glycidyl functional acrylic resin;

(c) blending of 2-9 % epoxy resin with the above siloxane oligomer grafted glycidyl functional acrylic resin obtained in step (b) above including blending said epoxy resin at any stage of the said process during –OH and glycidyl functional acrylic resin preparation step (a) or after step (a) and during preparation of siloxane oligomer grafted glycidyl functional acrylic resin to obtain said resin blend.

7. A process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition as claimed in claims 5 or 6 as cured clear and pigmented coating formulation wherein

(i) 40-90 wt. % of resin blend in said formulation including 2-9 % epoxy resin in said resin blend, and, rest siloxane oligomer grafted glycidyl functional acrylic resin in the resin blend, is cured with, (ii) 5-20 wt. % hardener/ curing agent including aminosilane hardener preferably 3-aminopropyltriethoxysilane (AMEO) in presence of preferably Dibutyltin dilaurate (DBTDL) as curing catalyst to enable clear and glossy films with flexibility and adhesion characteristics with due retention of gloss.

Dated this the 31st day of March, 2022 Anjan Sen
Of Anjan Sen and Associates
(Applicants Agent)
, Description:FIELD OF INVENTION
The present invention relates to protective hybrid polysiloxane clear and pigmented coating formulation/composition for Nickel-chromium plated and physical vapor deposited (PVD) metal alloys, and more particularly, the present invention relates to design of a protective clear hybrid polysiloxane based coating formulation suitable for nickel chromium (Ni-Cr) plated and physical vapor deposited (PVD) metal alloys used in faucets to enhance the service life. Also said pigmented formulation of the present invention is suitable for coating on mild steel substrate preferably as a topcoat over zinc silicate primer or epoxy primer.

BACKGROUND ART
Electrodeposited nickel is widely used in conjunction with chromium plating in different metal alloy as faucets for corrosion protection. Generally, faucets items are electroplated with Nickel plus chromium or copper plus Nickel plus chromium at defined individual thicknesses to impart both appealing surface decor and corrosion protection performance confirming to ASTM B458. PVD (physical vapour deposited) coated faucets bring rich aesthetic appeal and better performance. However, such Ni-Cr plating or PVD coating have limited corrosion protection performance. Other alternates reported to address this problem are based on pigmented organic coatings like powder coating or PTFE. However, such coatings spoil the original décor of the Ni-Cr or PVD coating.
These faucets are exposed to varying environmental conditions such as high humidity, saline atmosphere, chemicals and aggressive mechanical stresses in their service life. Such exposure to varying environmental conditions lead to rapid corrosion and consequent deterioration. As a result, many manufacturers and engineers of different industrial fields strive to improve the protective properties of Ni-Cr plated or PVD coated faucets. Most of the prior work is focused towards improving the quality of Ni-Cr plating or PVD coating thereby enhancing the durability of the faucet. There are attempts to enhance the durability through an additional layer of organic coatings like powder polyester, PTFE or PFE, however, all these approaches spoil the original décor and characteristic finish of Ni-Cr plating or PVD coating.
On the prior works, references are drawn to the following:
JP5180644B2 teaches nickel elution prevention method for copper alloy wetted parts wherein copper alloy wetted device is plated with nickel a protective film forming component containing benzotriazole and low-polymerized polyethylene.
JP2013083007A discloses a method for managing a treatment liquid for forming a protective film, with which the elution of nickel is prevented even when contact with a liquid such as tap water occurs, in a valve for an aqueduct, a valve for feeding water/hot water, a fitting etc. In a protective film forming process with an alkaline treatment liquid into which water of a washing process for cleaning a treatment liquid, used in a process for removing lead or/and nickel, mixes, the concentration of a component forming the protective film.
DE10257133A1 is directed to a chromium plated water faucet fitting that has inner fluoropolymer coating, to prevent chromium entering the drinking water with the water faucet fitting, especially hot/cold water mixers and shut-off assemblies, is metal with chromium plated visible surface. The inner surfaces, defining water flow paths, are coated with fluoropolymer to prevent chromium being deposited on them during plating; or the coating covers chromium deposits from the plating, to prevent chromium entering the drinking water.
CN106189561 discloses an environment friendly ceramic material for water faucet that is prepared according to a formula comprising raw materials at varying concentrations such as fluorocarbon resin, organosilicone oil, naphtha, polydimethylsiloxane, absolute ethyl alcohol, alkylphenol polyoxyethylene and other additives. The environment-friendly ceramic coating material for the water faucet has the advantages of corrosion resistance, wear resistance, high adhesive force, bright and clean appearance, and compact coating structure.
CN111518427 teaches a thermochromic coating composed of a faucet body, a primer coating and a thermochromic coating wherein the surface of the faucet body is uniformly coated with the thermochromic coating, the thermochromic coating being formed by uniformly spraying primer on the surface of the faucet body through a paint spraying machine, then baking the faucet body and then spraying a thermochromic material, and the thermochromic coating is an organic chromophoric coating with a chemical structure.
CN105778707 is directed to inner-wall protective coating for manufacturing faucet and relates to the technical field of hardware device processing and production. The inner-wall protective coating is characterized by being prepared from, by weight, modified epoxy resin, chitosan, wollastonite powder, carboxymethylcellulose, ethylene glycol dimethacrylate, triethylene glycol, anti-aging agent and other additives.
SU234093A1 teaches method for forming polymer coating on metal substrate and provides for an article comprising a substrate; a polymer coating; and an intermediate layer disposed between the substrate and the polymer coating, the intermediate layer comprising a carbon composite, wherein the carbon composite comprises carbon and a binder.
US20090048394A1 involves fast-curing modified siloxane compositions comprising an alkoxy- or silanol-functional silicone intermediate, at least one amine reactive ingredient selected from the group consisting of acetoacetate-functional ingredients, acrylate-functional ingredients, and mixtures thereof, an epoxy-functional ingredient, a curing agent selected from the group consisting of amines, aminosilanes, ketimines, aldimines and mixtures thereof, and water.
WO1996016109A is directed to epoxy polysiloxane made up of: (a) a resin component which includes a non-aromatic epoxy resin having at least two 1,2-epoxy groups per molecule; a polysiloxane and an organooxysilane; (b) an amine hardener component substituted in part or in whole by an aminosilane; (c) an organotin catalyst; and (d) an aggregate or pigment component. The hardener and epoxide resin react to form a cured linear epoxy polymer. The polysiloxane and/or organooxysilane undergo a hydrolysis reaction which produces silanol. The silanol undergoes polycondensation forming a linear epoxy-modified polysiloxane polymer. Thus, teaches epoxy polysiloxane together with a hardener component without the involvement of any acrylic polyol component in the epoxy polysiloxane resin.
WO2019107124 teaches providing a coating material composition which can form a coating film which can maintain appearance and gloss over a long period of time, and has high coating film hardness and flexibility, and excellent adhesiveness to an epoxy resin anticorrosive coating film. The acrylic polysiloxane resin coating material composition of this prior art contains: a silicone resin (A); a compound (B) having one or more functional groups capable of the Michel addition reaction with an unsaturated double bond in an acryloyloxy group, and one or more alkoxy groups bonded to silicon; an aliphatic urethane acrylate oligomer (C) having a cyclic structure and having three or more functional groups; and a di-functional acrylate monomer (D) not having an ether structure (provided that the ether structure in the acryloyloxy group is excluded) or an aromatic ring, wherein the mass ratio of the total amount of the compounds (A) and (B) to the total amount of the acrylate oligomer and the acrylate monomer is 40:60-70:30. This prior art is based on the involvement of urethane oligomer.
Polyurethane and/or Polysiloxane modified Epoxy Based on Acrylic Polyol and Tolonate, by Evi Triwulandari Indonesian Institute of Sciences January 2013, Conference: The International Conference on the Innovation in Polymer Science and Technology 2013 (IPST2013) Yogyakarta, Indonesia, October 7–10, 2013 At: Yogyakarta, Indonesia, discloses hybrid coating products that were synthesized from polyurethane and/or polysiloxane modified epoxy based on acrylic polyol and tolonate. Hybrid coating which synthesized were epoxy-polyurethane, epoxy-polysiloxane and epoxy-polyurethane-polysiloxane. Hybrid coating from epoxy-polyurethane was synthesized by reacting epoxy, acrylic polyol and tolonate.
IN201821049328/WO2020139642 is directed to a curable silicone-based composition comprising a hybrid silicone polymer, a catalyst, and a filler. In embodiments, this prior technology provides a curable silicone composition comprising a polymer A comprising an organic molecule or a siloxane molecule comprising an alkoxy radical, a hydroxyl radical, an isocyanate radical, a primary amine, or a carboxylic radical even epoxy radical; optionally a polymer B comprising an organic molecule, a siloxane molecule, or a hybrid-siloxane molecule; a catalyst; and a filler.
CN102304323 teaches a room temperature curable Ph silicone resin conformal coating material containing: (A) Ph silicone resin-linear polysiloxane block copolymer or Me Ph silicone-linear polysiloxane block copolymer 40-88, (B) alkoxysilane (R2 4-x547Si(OR1)x) 1-10, (C) amino- or epoxy-containing silane coupling agent 0.2-5, (D) organic Ti compound 0.05-3, (E) organic phosphate flame retardant synergist 0.02-0.2, and (F) organic hydrocarbon solvent or low mol. wt. siloxane 10-58 wt.%. Does not include any epoxy polysiloxane nor any acrylic polyol component in the epoxy polysiloxane.
CN112300680 teaches thermal insulation coating comprising sealing layer, reflective thermal insulating layer and weather-resistant surface layer, wherein the sealing layer is formed by an epoxy sealing primer or an anticorrosive primer, the reflective heat insulation layer is formed by polyurethane intermediate paint containing A1 component and B1 component, wherein the A1 component includes polyether polyol, silicone epoxy hybrid resin, hydroxy acrylic resin, filler, and film forming aid Agent M, solvent E, and the B1 component includes hexamethylene diisocyanate trimer, triethoxyaminosilane, and solvent F, the weather-resistant surface layer is formed by a fluorocarbon topcoat containing A2 component and B2 component, wherein, the A2 component includes flexible fluorocarbon resin, nano-titanium dioxide, flaky aluminum powder, aluminum silver paste, film-forming assistant N, and solvent G, the B2 component contains crosslinking agent and solvent H. The reflective thermal barrier layer, as per its A1 component is stated to comprise in parts by mass: 45-65 parts of polyether polyol, 4-14 parts of organic silicon epoxy hybrid resin, 4-14 parts of hydroxyl acrylic resin, 15-36 parts of filler, 0.5-5 parts of film-forming assistant M and 0.5-4 parts of solvent E. The silicone epoxy hybrid resin of this prior art does not have the acrylic polyol component in the same backbone with select epoxy equivalent levels.
US5472999 describes resin where there is a direct chemical bonding between the acrylic and the epoxy resin that is thus directed to aqueous resin dispersion which comprises as the chief component acrylic-modified epoxy-polyamine resin composed of a bisphenolic epoxy resin containing at least two epoxy groups per molecule; and, as bound to at least a part of said epoxy groups, is an acrylic resin having on the average at least one functional group which is capable of reacting with said epoxy group, per molecule, the molecular weight distribution of said acrylic resin as expressed by its weight average molecular weight (Mw)/number average molecular weight (Mn) being within a range of 1 to 1.2, and an active hydrogen-containing amino compound. Said aqueous resin dispersion may further optionally contain non-ionic, film-forming resin. Such dispersions are useful for cationic electrodeposition paint which can form a coating excelling in weatherability and corrosion resistance. Does not incorporate any aminosilane, the primary hydroxyl equivalent is 400-700 and the epoxy resin content is 10 to 20% and in this prior art there is reaction between epoxy and acrylic resin.
CN 113105571 A describes water borne acrylic containing DAAM-ADH or GMA-ADH crosslinking and presence of epoxy resin where the incorporation of siloxane is via vinyl silane monomer. This is a self-crosslinking one component system with the preferred cross linker being adipic dihydrazide relating to a water based system and also does not relate to any two-component system.
US6987144B2 teaches a polyol of the composition that has a -OH value in the range of 100 to 200 mg KOH/g wherein the polyol content is 0.1-30% and involves the hardeners of aminoplast resin, a polyisocyanate, a blocked polyisocyanate compound, a polyepoxide, a polyacid, and a polyol.
US4615947A teaches containing a thermoplastic or thermoset acrylic homogeneously admixed with an organopolysiloxane constituent that increases the adhesion of abrasion and solvent resistant organopolysiloxane hardcoats to thermoplastic substrates, and hence teaches an admixture of organosiloxane constituents.
WO2001009259A1 teaches compositions are provided which are formed from components comprising (a) at least one polysiloxane comprising at least one reactive functional group; (b) at least one reactant comprising at least one functional group that is reactive with at least one functional group selected from the at least one reactive functional group of the at least one polysiloxane and at least one functional group of at least one reactant; and (c) a plurality of particles, wherein each component is different, and wherein the at least one reactive functional group of the at least one polysiloxane and the at least one reactive functional group of the at least one reactant are substantially nonreactive with the particles. The hardeners involved are mentioned in this prior patent are aminoplast resin, a polyisocyanate, a blocked polyisocyanate compound, a polyepoxide, a polyacid, and a polyol but not aminosilane.
Reference is drawn to US4681811 wherein glycidyl functional acrylic is cured with an acid functional curing agent and does not involve aminosilane as curing agent. Further the acrylic of this prior art can contain an acrylic silane or a mercaptosilane to impart hydrolysable silane groups.
While there have been attempts in the state of the art towards improving the quality of Ni-Cr plating or PVD coating thereby enhancing the durability of the faucet, there is a further need to explore for formulations that would not only retain the original décor and characteristic finish of Ni-Cr plating or PVD coating but would further enhance the corrosion protection performance of the faucet, so that such formulations, would curtail the need to enhance the durability through an additional layer of organic coatings like powder polyester, PTFE or PFE that spoil the original décor and characteristic finish of Ni-Cr plating or PVD coating.
Hence there is a need in the art to provide for polymeric clear coating formulations/ composition that would retain the original décor and characteristic finish of Ni-Cr plating or PVD coated substrates and yet would further enhance the corrosion protection performance of the faucet. Also, there is a need in the art to provide for said polymeric formulations as pigmented coating formulations as an isocyanate free high durable pigmented coating for mild steel substrate preferably as a topcoat over zinc silicate primer or epoxy primer.
OBJECTS OF THE INVENTION
It is thus the basic object of the Applicants present invention to provide for a hybrid polymeric clear and pigmented coating formulation/composition based on an epoxy polysiloxane resin blend having acrylic polyol component and select epoxy equivalents, an amino silane curing agent and an accelerator which clear coating would enable excellent adhesion to Ni-Cr plated or PVD coated surface, to not only preserve original appearance of the faucet but would also enhance the corrosion resistance performance of the faucet.
It is another object of the present invention to provide for said pigmented highly durable coating formulations with high scratch hardness and flexibility which is ambient drying and free of isocyanates which can be applied over mild steel substrate preferably as a topcoat over zinc silicate primer or epoxy primer.
It is yet another object of the present invention to provide for said hybrid polymeric clear and pigmented coating formulation/composition as 2K (two component coating formulation) wherein said resin blend involves epoxy resin blended with the base acrylic resin as the first component of said formulation with the hardener preferably being aminosilane component as second component of said formulation.
It is another object of the present invention to provide for a high durable low thickness clear and pigmented coating which would provide corrosion resistance in copper accelerated acetic acid salt spray (CASS); ASTM B368 and salt spray (ASTM B117).
It is still another object of the present invention to provide for low surface energy and high contact angle based said clear coating formulation/composition that would cause the water droplets to easily spread over the surface, would provide good adhesion over Ni-Cr plated and PVD faucet, and would also provide high abrasion resistance, impact strength and flexibility.

SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a hybrid polysiloxane clear and pigmented coating formulation/composition comprising
(i) 40-90 wt. % of resin blend including 2-9% epoxy resin/s, and, siloxane oligomer grafted glycidyl functional acrylic resin, said acrylic resin comprising a reaction product of hydroxyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g and silanol and alkoxy functional organosiloxane resin;
(ii) 5-20 wt. % hardener including aminosilane hardener.
Preferably said hybrid polysiloxane clear and pigmented coating formulation/composition is provided as a two component system involving stable flowable resin blend (i) wherein said epoxy resin/s of said resin blend is preferably at least one cycloaliphatic epoxy resin or combinations thereof, said resin blend including siloxane oligomer grafted glycidyl functional acrylic resin comprising silanol and alkoxy functional organosiloxane resin grafted onto base hydroxyl and glycidyl functional acrylic resin enabling said siloxane oligomer grafted glycidyl functional acrylic resin overall having 2-9 % epoxy percent on resin solids, 10-40% silicone % on resin solids, and epoxy equivalent wt. in the range of 300-900 g/ eq. suiting pigmented formulation preferably 500-700 g/ eq., suiting clear formulation; and
wherein said silicone oligomer grafted glycidyl functional acrylic resin comprises hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g stabilized by incorporation of mono-functional alcohol including monofunctional alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol preferably isobutanol; and
wherein the balance ingredients of said formulation being conventional paint ingredients including solvents.
Preferably in said hybrid polysiloxane clear and pigmented coating formulation/composition said siloxane oligomer grafted hydroxyl and glycidyl functional acrylic resin of component (i) is a reaction product of
(a) 60-90 wt.% hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g, and,
(b) 10-40 wt.% of organosiloxane oligomer with methoxy functionality enabling epoxy equivalent wt. in the range of 300-900 g/eq. more preferably 500-700 g/ eq. of said siloxane oligomer grafted base hydroxyl and glycidyl functional acrylic resin.
According to another preferred aspect of the present invention there is provided said hybrid polysiloxane clear and pigmented coating formulation/composition wherein said hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g is a polymer of monomers including esters of acrylic/methacrylic acid, hydroxy functional and glycidyl functional acrylate monomers including monomers of 0-10 % Methyl methacrylate, 3-14 % Butyl Acrylate, 0-5 % Butyl Methacrylate, 5-35 % Glycidyl Methacrylate (GMA), 0-15 % Hydroxyethyl methacrylate (HEMA), hydroxyl ethyl acrylate 0-15 % (HEA).
According to another aspect of the present invention there is provided a process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition comprising the steps of providing
(i) 40-90 wt. % of resin blend including 2-9 % epoxy resin & siloxane oligomer grafted glycidyl functional acrylic resin, said acrylic resin obtained by reacting hydroxyl and glycidyl functional base acrylic resin having -OH value in the range of 50 to 150 mg KOH/g with silanol and alkoxy functional organosiloxane resin;
(ii) 5-20 wt. % hardener including aminosilane hardener;
(iii) curing the resin blend of (i) with (ii) in the presence of catalyst preferably Dibutyltin dilaurate (DBTDL) and obtaining therefrom clear/pigmented and glossy films with flexibility and adhesion characteristics and retention of gloss.

Preferably is said process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition said resin blend of step (i) including epoxy resin/s & siloxane oligomer grafted glycidyl functional acrylic resin is obtained based on the following steps of

(a) Radical polymerizing mixture of monomers including esters of acrylic/methacrylic acid, hydroxy functional and glycidyl functional acrylate monomers including monomers of 0-10 % Methyl methacrylate, 3-14 % Butyl Acrylate, 0-5 % Butyl Methacrylate, 5-35 % Glycidyl Methacrylate (GMA), 0-15 % Hydroxyethyl methacrylate (HEMA), hydroxyl ethyl acrylate 0-15 % (HEA) in organic solvents including butyl acetate, cellosolve acetate, xylene as solvents with initiator including TBPB (Tertiary butyl perbenzoate) as initiator in the presence of nitrogen and heating in temperature range of 140-150 deg C wherein said mixture of monomers and initiator are added dropwise over 4 hours by maintaining temperature range of 140-150 deg C followed by carrying out digestion for 3 hours at 140-150 deg C with addition of extra initiator during last hour of digestion and obtaining therefrom both –OH and glycidyl functional acrylic resin having -OH value in the range of 50 to 150 mg KOH/g;
(b) condensation polymerizing –OH and glycidyl functional acrylic resin of step (a) above with silanol and alkoxy/methoxy/ethoxy functional organosiloxane resin involving tetra isopropyl titanate catalyst by starting heating at 60?C followed by adding the mixture of organosiloxane resin in the presence of mono-functional alcohol dropwise to the resin and said catalyst over a period of 30 to 40 minutes while continuing to stir and maintaining temperature at 60-70?C and thereafter gradually heating the contents to 120?C over a period of 1-3 hours at 120 ?C and maintaining temperature while stirring to attain single phase clear droplet indicating reaction termination to obtain methanol/ethanol as by-product and siloxane oligomer grafted glycidyl functional acrylic resin;
(c) blending of 2-9 % epoxy resin with the above siloxane oligomer grafted glycidyl functional acrylic resin obtained in step (b) above including blending said epoxy resin at any stage of the said process during –OH and glycidyl functional acrylic resin preparation step (a) or after step (a) and during preparation of siloxane oligomer grafted glycidyl functional acrylic resin to obtain said resin blend.
More preferably in said process for preparing hybrid polysiloxane clear and pigmented coating formulation/composition as cured clear and pigmented coating formulation wherein
(i) 40-90 wt. % of resin blend in said formulation including 2-9 % epoxy resin in said resin blend, and, rest siloxane oligomer grafted glycidyl functional acrylic resin in the resin blend, is cured with, (ii) 5-20 wt. % hardener/ curing agent including aminosilane hardener preferably 3-aminopropyltriethoxysilane (AMEO) in presence of preferably Dibutyltin dilaurate (DBTDL) as curing catalyst to enable clear and glossy films with flexibility and adhesion characteristics with due retention of gloss.

DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention provides for hybrid polysiloxane clear and pigmented coating formulation/composition suitable for nickel chromium (Ni-Cr) plated and physical vapor deposited (PVD) metal alloys used in faucets to enhance the service life by imparting excellent adhesion to Ni-Cr plated or PVD coated surface, with said pigmented coating formulations being highly durable with improved scratch hardness and flexibility which is ambient drying and free of isocyanates suitable for application over mild steel substrate preferably as a topcoat over zinc silicate primer or epoxy primer; said coating formulation/ comprising:
(i) 40-90 wt. % of acrylic resin blend including 2-9 % epoxy resin, and, siloxane oligomer grafted glycidyl functional acrylic resin, said acrylic resin comprising a reaction product of hydroxyl and glycidyl functional acrylic resin having -OH value in the range of 50 to 150 mg KOH/g and silanol or alkoxy functional organosiloxane resin;

(ii) 5-20 wt. % hardener including aminosilane hardener, curable at ambient or at elevated temperatures.
In the present invention there is no reaction between acrylic resin that is formed by polymerization, and epoxy resin (preferably cycloaliphatic epoxy resin) of the resin blend, which epoxy resin could be blended with the glycidyl functional acrylic monomers during polymerization of the acrylic monomers leading to –OH and glycidyl functional acrylic resin contained in the blend having therein the epoxy resin, which acrylic resin of the blend is further grafted with siloxane oligomers enabling siloxane oligomer grafted glycidyl functional acrylic resin contained in said blend.
Thus said –OH and glycidyl functional acrylic resin of the blend is reacted with the silanol and alkoxy/methoxy/ethoxy functional organosiloxane resin that is contained in the blend, which blend is further cured with an aminosilane hardener. The amine group of the aminosilane hardener preferably reacts with both the oxirane group of the epoxy resin and the oxirane group of the glycidyl functional acrylic resin, to provide for the desired attributes of gloss retention together with desired mechanical properties and flexibility at about half the levels of siloxane content (˜35%) comparable to the attributes of conventional epoxy polysiloxane resin with high content of siloxane (70%).
While most of the prior work is focused towards improving the quality of Ni-Cr plating or PVD (physical vapor deposited) coating thereby enhancing the durability of the faucet, and since to enhance the durability attempts were made through an additional layer of organic coatings like powder polyester, PTFE or PFE, however, all these approaches spoil the original décor and characteristic finish of Ni-Cr plating or PVD coating. However, the hybrid polysiloxane clear and pigmented coating formulation/composition of the present invention could not only achieve the desired gloss retention but also the desired flexibility and mechanical properties at much low levels of siloxane content that is not only thus technically advanced in light of the prior art problems by eliminating additional layers of organic coatings that compromises on the gloss, flexibility and adhesion characteristics of the resinous coating but also brings economy to the resin based coating formulation/composition.
The glycidyl functional acrylic resin of the resin blend of hybrid polysiloxane clear and pigmented coating formulation/composition of the present invention includes a low -OH value of 50 to 150 mg KOH/g hydroxyl and glycidyl functional acrylic resin that results in siloxane oligomer grafted glycidyl functional acrylic resin of said resin blend and it is preferred that the epoxy resin included in said resin blend is added in the formulation prior to reaction with silanol or alkoxy functional organosiloxane resin and curing, preferably in the levels of 2-9% to obtain desired properties of durability, flexibility and mechanical properties.
Preferably, in said clear and pigmented hybrid polysiloxane based coating formulation said organosiloxane based glycidyl functional acrylic resin of the resin blend is the key film forming material together with select levels of epoxy resin in the said resin blend which when cured with hardeners/curing agents/ cross-linkers such as amino silanes, blocked amino silanes, amino functional polysiloxanes gave the desired coating attributes;
and wherein accelerators/catalysts are selected from Dibutyltin dilaurate (DBTDL) and Organic titanates in the proposed coating composition to improve crosslinking as well as improve efficacy of reaction, scratch resistance, hardness and adhesion with various substrates.
Examples:
Comparative Example 1 (Not according to the present invention): A epoxy polysiloxane resin with only cycloaliphatic epoxy resin (with EEW of 220 to 240 g/eq.) and organosiloxane resin is synthesized as per the following procedure. 30% epoxy resin and 70% polysiloxane resin (Dow Corning 3074) is taken in the reactor and heated to 120 deg C till desired clarity and viscosity is attained. Ortho xylene and isobutanol are taken as solvents. 2-ethylhexanoic acid is taken as the catalyst. A resin is prepared with 70% solids and EEW of 500-600 g/eq. and a Gardner viscosity of R-S.
Example 2 to 10: The recipes are given in Table 1 for Examples 2-7. Example 3, 9, 10 is in according to the present invention. Other examples (2 and 4 to 7) are not according to the present invention. Acrylic resin (both -OH functional and Epoxide functional) was synthesized using HEMA (Hydroxy ethyl methacrylate) or HEA (Hydroxy ethyl acrylate) and GMA (glycidyl methacrylate) as monomers in solvent (butyl acetate/cellosolve acetate/xylene) with TBPB (Tertiary butyl perbenzoate) as initiator. The siloxane oligomer can be blended or grafted onto the acrylic backbone. In the listed examples, blend of acrylic resin and the siloxane oligomer is incompatible and leads to haze and phase separation. Hence the siloxane oligomer is grafted onto acrylic resin via a condensation polymerization reaction using titanate catalyst. The hydroxyl groups of the acrylic resin combine with the methoxy/ethoxy groups of the siloxane oligomer. Methanol/ethanol is the by-product of the condensation reaction. Epoxy resin is then blended into the above recipe. The epoxy resin can be blended in the resin at any stage of the resin preparation process (during acrylic resin synthesis, after preparation of the acrylic, after preparation of the acrylic siloxane reaction intermediate). Addition of a mono-functional alcohol improves the storage stability of the system. Resin was cured with 3-aminopropyltriethoxysilane (AMEO) and DBTDL catalyst (AHEW = 110.5) as per stoichiometry.

Part A procedure: The recipes are given in Table 1. Example 3 is in according to the present invention. Other examples (2 and 4 to 7) are not according to the present invention. Charge solvent to the reactor (4 neck glass flask with stirrer, nitrogen supply inlet, temperature sensor and condenser). Start stirring at 150 rpm. Start water supply to condenser. Start heating to 140-150 deg C. Add mixture of monomers and initiator dropwise over 4 hours maintaining Temp at 140-150 deg C. Carry out digestion for 3 hours at 140-150 deg C. Add extra initiator during last hour of digestion. Stop the heating, continue stirring and discharge and filter the batch at suitable temperature (70-80 deg C).
Part B procedure: The recipes are given in Table 2. Charge the acrylic resin made in Part A in the reaction vessel. Start water supply to condenser and flow of nitrogen gas to the reactor. Start stirring and add TYZOR TPT catalyst (tetra isopropyl titanate) to the reactor. Start heating to 60?C. Add the mixture of organosiloxane oligomer (Dow Corning DC 3074) and mono-functional alcohol dropwise to the resin and catalyst mixture over a period of 30 to 40 minutes while continuing to stir and maintaining temperature at 60-70?C. Gradually heat the contents to 120?C over a period of 1 hour. Maintain at this temperature while continuing to stir. During this time remove a small drop with a glass rod on a clear glass plate to check if a single-phase clear droplet is obtained. As soon as a clear drop is obtained (1 to 3 hours at 120?C), stop the heating, while continuing to stir. Filter/ discharge the batch at a suitable temperature (70-80 deg C).
The final EEW is contributed by the epoxy resin and glycidyl functional acrylic resin of the resin blend, as there is no reaction between silanol and alkoxy/methoxy/ethoxy of the siloxane with the glycidyl group of the acrylic resin. Table 1 indicates the final resin epoxy value.
Table 1
S.NO. RAW MATERIAL % 2 3 4 5 6 7 8 9 10
Part A EXPERIMENTS: (of acrylic resins: –OH and epoxide functional)
1 Methyl methacrylate 4.50 2.50 1.50 3.00 7.00 4.50 0.00 0.00 3.20
2 Butyl Acrylate 9.00 9.50 11.00 6.50 4.00 6.60 6.80 11.00 8.50
3 Butyl Methacrylate 4.50 4.00 1.30 0.00 2.70 2.50 2.30 1.50 2.00
4 Glycidyl Methacrylate 9.00 15.00 21.20 21.20 21.20 21.20 34.00 24.00 11.50
5 Hydroxy ethyl acrylate 0.00 0.00 0.00 12.80 0.00 0.00 9.40 0.00 0.00
6 Hydroxyethyl methacrylate 6.50 7.50 8.50 0.00 8.60 8.70 0.00 9.00 6.30
7 Tertiary butyl perbenzoate 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00 3.00
8 Cellosolve acetate 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
9 o-XYLENE 14.45 14.45 14.45 14.45 14.45 14.45 14.45 14.45 14.45
10 BUTYL ACETATE 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00
11 Cycloaliphatic epoxy resin 10 5 0 0 0 0 5 5 5
Part B EXPERIMENTS: (modification with siloxane oligomer)
12 Dow Corning DC 3074 24.5 24.5 24.5 24.5 24.5 24.5 10.5 17.5 31.5
13 TYZOR TPT 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
14 ISOBUTANOL 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5
15 TOTAL 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00
EEW (g/eq.) of Resin 665 670 670 670 670 670 350 470 800
OH value (mg KOH/g) of intermediate Step A Acrylic Resin 84 84 84 142 96 86 86 86 86
Tg ?C 15 15 15 10 25 30 15 15 15
% Solids 70 70 70 70 70 70 70 70 70
%Siloxane 35 35 35 35 35 35 15 25 45
Film appearance (visual) Clear, glossy Clear, glossy Clear, glossy Clear, glossy Clear, glossy Clear, glossy Clear, glossy Clear, glossy Clear, glossy
Adhesion (using cross-cut adhesion test)
Pass Pass Fails Fails Fails Fails Fails Pass Pass
Flexibility (Using conical mandrel test)
Pass Pass Fails Fails Fails Fails Fails Pass Pass

Hydroxy ethyl acrylate has a lower Tg compared to hydroxy ethyl methacrylate. For a high -OH value resin with a desired Tg as per Resin 5 of the above Table 1, in some cases hydroxy ethyl acrylate is preferred.
All the resins are cured preferably with 3-aminopropyltriethoxysilane (AMEO) as curing agent as per stoichiometry and DBTDL as curing catalyst. As seen from the above Tables, clear and glossy films are obtained. Select contents of cycloaliphatic epoxy resin were surprisingly found to provide good film flexibility and adhesion as seen from examples 2, 3, 9, 10.
Table 2: Resin parameters of the paints based on different resins
Properties 1 Conventional epoxy-polysiloxane resin as comparative of Example 1 2 of Table 1 3 of Table 1 4 of Table 1
Preferred epoxy equivalent weight g/eq. 600-700 600-700 600-700 600-700
Silicone percent (on solids) 70 35 35 35
Epoxy percent (in formula from blended epoxy resin) 30 10 5 0
%NVM 70 70 70 70

The paint formulation is given in Table 3. The paint is prepared in a high-speed disperser. The physical parameters of the paint are given in Table 4 and the mechanical properties and durability data are given in Table 5 and 6 respectively. Paint of example 4 is not prepared as the resin itself is failing flexibility on conical mandrel in clear coat testing.
Table 3: Paint formulation
S.NO. RAW MATERIAL % by wt. Weight (g)
1 RESIN Acrylic Polysiloxane resin 25
2 Disperbyk 163 Dispersing agent 0.3
3 BYK 085 Siloxane based defoamer 0.2
4 Butyl acetate Solvent 4
5 Aerosil R972 Fumed Silica 1.5
6 TiO2 R902 plus Titanium Dioxide pigment 23.8
7 RESIN Acrylic Polysiloxane resin 29.8
8 TINUVIN 292 Hindered Amine light stabilizer 0.4
9 TINUVIN 1130 UV Absorber 0.9
10 Dibutyl tin dilaureate Curing catalyst 0.1
11 Triethylorthoformate Moisture scavenger 2
12 o-xylene Solvent 4
13 AMEO (3-aminopropyl triethoxysilane) Curing agent 8

Epoxy resin
The at least one cycloaliphatic epoxy resin compound comprises 1,4-cyclohexanedimethanol epoxy resin, or a mixture of 1,3-cyclohexanedimethanol epoxy resin and 1,4-cyclohexanedimethanol epoxy resin; a hydrogenated bisphenol A epoxy resin; or combinations thereof. Epoxy equivalent weight is in the range of 200 to 400 g/eq. The resin of the present invention works well with the said variants and their combinations.

Curing agents
Non-limiting examples of aminosilanes that may be used include aminopropyl trimethoxysilane, aminopropyl triethoxysilane, aminoethyl trimethoxysilane, aminoethyl triethoxysilane, methylaminopropyl trimethoxysilane, aminobutylmethyl dimethoxysilane, aminopropyl dimethyl methoxysilane, aminopropylmethyl dimethoxysilane, aminopropyldimethyl ethoxy silane, aminobutylmethyl dimethoxysilane, bis- (gamma-trimethoxysilylpropyl) amine, N- (3-methacryloxy-2-hydroxypropyl) -3-aminopropyl triethoxysilane, N- (3-acryloxy-2-hydroxypropyl) -3-aminopropyl triethoxysilane, (N, N-dimethylaminopropyl) trimethoxysilane, (N, N-diethyl-3-aminopropyl) trimethoxysilane, diethylaminomethyl triethoxysilane, bis (2-hydroxyethyl) -3-aminopropyl triethoxysilane, ?-aminopropyl trimethoxysilane, N- (2'-aminoethyl) -3-aminopropyl trimethoxysilane, N- (2'-aminoethyl) -3-aminopropyl triethoxysilane, N-Butyl-3-Aminopropyl triethoxysilane, N-octyl-3-aminopropyl trimethoxysilane, N-cyclohexyl-3-aminopropyl triethoxysilane, N- (3'-triethoxysilylpropyl) -piperazine, bis- (3-triethoxysilylpropyl) amine, tris- (3-trimethoxysilylpropyl) amine, N, N-dimethyl-3-aminopropyl triethoxysilane, N-methyl-N-butyl-3-aminopropyl triethoxysilane, N- (3'-aminopropyl) -3-aminopropyl triethoxysilane, N- (3'-triethoxysilylpropyl) morpholine, N-phenyl-gamma-aminopropyl trimethoxysilane and N-phenyl-gamma-amino-2-methylpropyl trimethoxysilane. All the curing agents and their combinations are workable for the purposes of the present invention.

Catalyst
In general, the coatings are capable of curing under ambient temperature and humidity conditions to a tack-free coating in 2 to 20 hours even without such a catalyst, but a catalyst may be preferred to give a faster cure. One example of a catalyst for Si—O—Si condensation is an alkoxytitanium compound, for example a titanium chelate compound such as a titanium bis(acetylacetonate) dialkoxide, e.g. titanium bis(acetylacetonate) diisopropoxide, a titanium bis(acetoacetate) dialkoxide, e.g. titanium bis(ethylacetoacetate) diisopropoxide, or an alkanolamine titanate, e.g. titanium bis(triethanolamine) diisopropoxide, or an alkoxy titanium compound which is not a chelate such as tetra(isopropyl) titanate or tetrabutyl titanate. The titanium compound can for example be used at 0.1 to 5% by weight of the binder. Corresponding alkoxide compounds of zirconium or aluminium are also useful as catalysts. An alternative catalyst is a nitrate of a polyvalent metal ion such as calcium nitrate, magnesium nitrate, aluminium nitrate, zinc nitrate or strontium nitrate. The level of calcium nitrate catalyst required is generally not more than 3% by weight of the binder, for example 0.05 to 3% by weight. Another example of a suitable catalyst is an organotin compound, for example a dialkyltin dicarboxylate such as dibutyltin dilaurate or dibutyltin diacetate. Such an organotin catalyst can for example be used at 0.05 to 3% by weight of the binder of the coating composition. Other compounds effective as catalysts in the coating compositions of the invention are organic salts, such as carboxylates, of bismuth, for example bismuth tris(neodecanoate). Organic salts and/or chelates of other metals such as zinc, aluminium, zirconium, tin, calcium, cobalt or strontium, for example zirconium acetylacetonate, zinc acetate, zinc acetylacetonate, zinc octoate, stannous octoate, stannous oxalate, calcium acetylacetonate, calcium acetate, calcium 2-ethylhexanoate, cobalt naphthenate, calcium dodecylbenzenesulphonate or aluminium acetate, may also be effective as catalysts.

Acrylic monomers
According to yet another preferred aspect of the present invention said coating composition is provided wherein said acrylic polyol comprises vinyl monomers, more specifically esters of acrylic or methacrylic acid including acrylates of alkyl, cycloalkyl, or aryl acrylates and methacrylates and aromatic vinyl compounds including styrene or multifunctional acrylic monomers such as diacrylates or triacrylates.
According to another preferred aspect of the present invention there is provided a coating composition wherein said acrylic polyol comprises hydroxyl monomers including hydroxyalkyl acrylates and hydroxyalky methacrylates such as 2-hydroxyethyl acrylate, 2- hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxpropyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, allyl and methally alcohol, butyl hydroxyethyl maleate and fumarate, butyl hydroxypropyl maleate and fumarate, including acetoacetate monomers such as acetoacetate ethyl methacrylate.
According to another preferred aspect of the present invention there is provided a coating composition wherein said acrylic polyol comprises epoxy functional monomers such as glycidyl acrylate and glycidyl methacrylate. One of the preferred epoxy-functional acrylic monomers is glycidyl methacrylate.
According to yet another preferred aspect of the present invention there is provided said coating composition comprising solvent or mixture of solvents upto 30 percent of the ingredients of the composition wherein said solvents include amyl acetate, toluene, ethyl acetate, butyl acetate, methoxy propyl acetate, acetone, methyl isobutyl ketone, methyl ethyl ketone, methyl amyl ketone, mineral spirits, ethylene glycol monoether acetates and other aliphatic, cycloaliphatic and aromatic hydrocarbons, such as xylene, esters, ethers, ketones, and other compatible solvents and reactive diluents of Cardura E10. The monomer variants and the solvent variants are all workable for the purposes of the present invention to give the desired results.

Polymerization Initiators
The free radical polymerization used to form the acrylic backbone is preferably carried out using conventional techniques, such as by heating the monomers in the presence of a free radical polymerization initiator, typically, tertiary butyl perbenzoate, tertiary butyl peroctoate, cumene hydroperoxide, benzoyl peroxide, di-tertiary butylperoxide, di-cumene peroxide, methyl ethyl ketone peroxide or similar peroxy compounds, or an azo compound such as azobisisobutyronitrile is employed. The amount of free radical polymerization initiator can be varied depending upon the desired molecular weight but 0.05-8 percent by weight based on the weight of total polymerizable monomers is typical. A preferred range is from 0.05 to 4 percent by weight. A mixture of two or more initiators may be used.

Table 4: Physical parameters of paint based on various resins

Properties 1 2 3
Finish on Hegman gauge 7+ 7+ 7+
Shade White White White
Drying Characteristics @ 30°C
Surface Dry
Nail Hardness

4 hrs
12 hrs

4 hrs
12 hrs

2.30 hrs
8 hrs
Gloss @60° 94-95 85-86 91-92

Table 5: Mechanical properties of paint based on various resins
Substrate type : 6 x 4 inches Sa 2½ MS burnished panel
Surface preparation : Cleaned with Solvent
System Applied : 1st coat- 2K Acrylic Polysiloxane -1 X 75 µ
Properties Test Method 1 2 3


Cross cut adhesion after 24 hrs air drying(Burnished MS Panels) ASTM D 3359 Method B 3B 3B 3B


Cross cut adhesion after 7 days air drying(Burnished MS Panels) ASTM D 3359 Method B 3B 3B 3B


Cross cut adhesion after 24 hrs air drying (Applied on 1 coat of Rust-O-Cap Epoxy primer) ASTM D 3359 Method A 5A 5A 5A


Cross cut adhesion after 24 hrs air drying.( Applied on 1 coat of Apcodur EHB Zinc Phosphate primer) ASTM D 3359 Method A 5A 5A 5A


Erichsen Impact Test ( 0.908 Kg / 83 cm ) after 48 hrs air dry applied ASTM D 2794 Face-Passes Face-Passes Face-Passes
Conical Mandrel after 7 days(applied on tin panel ) ASTM D 522 Passes 1/8th inches Passes 1/8th inches Passes 1/8th inches
Scratch hardness tester after 7 days IS 101 Part 5, Sec 2/88 3000 g 3000 g 3000 g

Table 6: GLOSS RETENTION IN QUV B 313

Substrate type : 6 x 3 x 1.2 mm Sa 2½ MS burnished panel.
System Applied: 1st coat- Rust-O-Cap (PC 1222 Epoxy primer) - 1 X 75 micron
2nd coat- 2 K polysiloxane - 1 X 80 micron

Sr.No. Hours of exposure 1 2 3


1 100 100% 89% 99%
2 200 100% 89% 98%
3 300 100% 89% 96%
4 400 99% 89% 95%
5 500 98% 89% 94%
6 600 97% 88% 94%
7 700 97% 86% 93%
8 800 97% 85% 92%
9 900 95% 81% 91%
10 1000 95% 80% 90%
11 1100 95% 78% 88%
12 1200 95% 76% 87%
13 1300 93% 74% 86%
14 1500 90% 58% 81%
15 1700 86% 57% 78%
16 2000 78% 50% 75%
17 2300 76% 40% 70%
18 2500 75% 32% 67%

As can be seen from Table 6, the gloss retention of the system with 5% cycloaliphatic epoxy resin (Example 3) is superior to the gloss retention of the system with 10% cycloaliphatic epoxy resin (example 2) (both systems containing 35% siloxane) and at par with a 70% siloxane modified system which has 30% cycloaliphatic epoxy resin (Example 1- conventional epoxy-polysiloxane resin). This coating passes all the desired mechanical properties, flexibility as well as durability requirements.
The key attributes of the coating formulation/composition are the following:
a) Polysiloxane clear and pigmented coating composition can be either two component or three components;
b) Coating composition, when applied over metal surface, can be cured at ambient temperature or at set temperature by baking;
c) Key advantage is preserving the original décor and characteristic finish of Ni-Cr or PVD coating that is devoid of any additional layer of coating to attain the desired attributes;
d) Coating possesses very good adhesion over Ni-Cr plated and PVD surface;
e) Resulting coating is flexible and having good abrasion resistance properties that are coated on select faucets to enhance its service life;
f) Pigmented coating formulations are highly durable with improved scratch hardness and flexibility and is ambient drying and free of isocyanates suitable for application over mild steel substrate preferably as a topcoat over zinc silicate primer or epoxy primer
Thus, the two/ three component system based on organosiloxane as key film forming material of the present invention can either be ambient cured or cured at elevated temperatures.
Cross linkers such as amino silanes, blocked amino silanes, amino functional polysiloxanes found suitable to cure the coating. The silane compounds used to catalyze polysiloxane coatings are extremely effective adhesion promoters, resulting in tenacious adhesion over primers, metals, and concrete.
Organic titanate is used as accelerator/ catalyst in the said coating composition to improve crosslinking as well as improve efficacy of reaction, scratch resistance, hardness and adhesion with various substrates.
Importantly, it is possible by way of the present invention to drastically cut down on the siloxane oligomer to yet achieve the desired retention of gloss together with other mechanical characteristics of said resin together with adding economy to the resin wherein
the (i) the epoxy polysiloxane based hybrid resin blend - employed for the coating formulation of the present invention is based on the acrylic polysiloxane hybrids modified with only 35% organosiloxane intermediates/oligomers and yet retaining gloss similar to conventional epoxy polysiloxane resin having 70% siloxane content.
The intermediates are methyl/phenyl/propyl functional organopolysiloxanes with hydroxyl or alkoxy including ethoxy and methoxy functionality. This enabled to achieve high exterior durability. The epoxy equivalent weight (EEW) of this resin is about ~500-700 g/eq. that is preferred for clear coating formulations while epoxy equivalent wt. (EEW) in the range of 300-900 g/ eq. suits pigmented coating formulation of the present invention, said EEW varies based on the glycidyl monomer content by keeping the levels of epoxy resin/s in the resin blend in the levels of 2-9%.