Claims:WE CLAIM:

1. A modifier for a coating composition, the modifier comprising inorganic nanoparticles having at least one reactive functional group covalently bonded to a crosslinking agent, wherein the crosslinking agent is an organohydrosiloxane having at least one [—HSiR—O—] unit, each R being independently an alkyl group having 1 to 4 carbon atoms.

2. A modifier as claimed in claim 1, wherein the organohydrosiloxane has a general Formula I:

(I)

wherein R1, R2, R3, R4, R5, R6 and R7 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen, and
n =5 to 46,
such that the organohydrosiloxane has a molecular weight in a range of 1000 to 3500 Da.

3. A modifier as claimed in claim 1, wherein the organohydrosiloxane has a general Formula II:

(II)

wherein R1, R2, R3, R4, R6, R7, R8, R9 and R10 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen,
m=2-14, and
n=1-7
such that the organohydrosiloxane has a molecular weight in a range of 700 to 2500 Da.

4. A modifier as claimed in claim 1, wherein the molar ratio of the inorganic nanoparticles to the organohydrosiloxane is in a range of 65 to 155.

5. A modifier as claimed in claim 1, wherein the inorganic nanoparticles are selected from a group consisting of silica, alumina, titania, zirconia, clay and mixtures thereof.

6. A modifier as claimed in claim 1, wherein the reactive functional group is hydroxyl group.

7. A modifier as claimed in 1, further comprising one or more of a dispersing agent and a surface tension reducing additive

8. A coating composition comprising the modifier claimed in any of claims 1 to 7.

Dated this 7th day of April, 2017

Essenese Obhan
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 864
, Description:FIELD OF INVENTION
The present invention relates to a modifier for improving the surface properties of a coating composition. More particularly, the present invention relates to a modifier comprising inorganic nanoparticles bonded to a polymeric surface modifying agent.

BACKGROUND
The use of inorganic particles in coating compositions is widely known to improve the surface properties of the coatings. Such coating compositions however are subjected to drawbacks such as – haziness, gloss loss, brittleness etc. It is further desired that such coatings exhibit mar-resistance and resistance to environmental etching. Several methods of modifying the coating compositions have been devised to achieve one or more of these properties. To be commercially successful, a coating should provide as many favorable characteristics as possible. Accordingly, it is most preferable to produce a coating that has an optimum mix of characteristics with regard to resistance to various forms of damages. One of the techniques of improving the properties of the coating compositions employs modified inorganic particles such as silica. Silica is modified by coating the particle surface with crosslinked polysiloxane coating. Herein, the inorganic particles are, for example, grafted with a polysiloxane coating via a crosslinking agent. However, because the existing techniques represent a compromise, usually one or more properties are partially/ completely sacrificed to increase the other.

For example, EP 0832947 describes formation of a film forming binder system with improved abrasion resistance. The binder system consists of a crosslinkable resin and crosslinking agent. The nanoscale fillers are made surface reactive by the use of dual functional crosslinking agent (carbamate or glycidyloxy silane) having reactive end groups which are reactive to the polymeric phase. Thus the covalent attachment of the nanoscale fillers to the polymer matrix is made possible in this procedure. One of the disadvantage of this process is that high loading of the reactive nanoscale fillers is required for gaining improved scratch resistance which also leads to brittlement of the coating.

US patent 5853809 describes use of silica particle modified with carbide molecules and used in clear coats. The inorganic-organic hybrid mixture thus produced gives automotive coating system abrasion resistance. The nano particles thus produced require substantial amount of nano silica particles to obtain abrasion resistance property while curing the film above 130 ?C. Nano particles were modified with suitable functional agent and resin matrix binds chemically with nanoparticles which often lead to the brittleness in final coating.

US 7641972 describes modification of nano particles by use of trimethyl terminated polydimethylsiloxane hydride coupled with vinyl trimethoxysilane. It also teaches the reaction of silaplane based compound with caprolactone based monomer followed by further functionalization with isocyanatopropyltrimethoxysilane. The nano particles thus prepared is used for polyurethane based resin systems. The particle thus produced shows substantial enrichment of nano particles on the surface of the final film but unable to provide substantial surface hardness to obtain abrasion resistance property at relatively low temperatures. The film thus obtained also fails to exhibit, in particular, 0 hour mar resistance (i.e. immediately after baking).

WO 2006/114420 describes the modification of nano silica particle with the use of low molecular weight polydimethylsiloxane and tetraethylorthosilicate and use the same for acrylic melamine and 2K based polyurethane system. The invention describes use of very low amount of silica in the final resin system to get the required surface hardness. However, incorporation of nano silica particles into the 2K based resin system develops craters and also the gloss of coating at 20° reduces while comparing with blank system.

US 20150203716 A1 relates to a curable film-forming compositions comprising: (a) a polymeric binder comprising: (i) a polysiloxane having reactive functional groups and in which is dispersed protonated silica particles having an average particle size of 2 to 20 microns, wherein the polysiloxane is present in the polymeric binder in an amount of at least 10 percent by weight based on the total weight of solids in the polymeric binder; and (ii) optionally, at least one additional polymeric resin different from the polysiloxane (i), having reactive functional groups; and (b) a curing agent containing functional groups that are reactive with the reactive functional groups of (i), (ii), or both. After application to a substrate as a coating and after curing, the curable film-forming composition demonstrates an initial 85° gloss of less than 30 and an increase in 85° gloss of no more than 10 gloss units, or alternatively, 50 percent when subjected to abrasion test.

US 6803408 relates to a composition 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 the at least one reactant; and (c) a plurality of particles selected from inorganic particles, composite particles, and mixtures thereof, wherein each component is different. The inorganic particles may be surface treated.
US 6593417 relates to coating compositions 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 functional group of the at least one reactant are substantially nonreactive with the particles. Here, the additive prepared requires several steps to be followed and many reactants to be used, which makes the process lengthy, time consuming and difficult to practice.
Thus, there is a need to devise modifiers for coating compositions which exhibit abrasion and mar resistance without embrittlement, haziness, or other film defects. It is also desirable that such coatings have properties such as recoatability while requiring lesser loading of inorganic particles. It is further desirable that such a modifier exhibits the afore-said properties with both the 1K (one-component) and 2K (two-component) coating compositions based on polyurethane/ acrylic melamine or epoxy resin etc. It is also further desirable that such a modifier can be added in the commercial coating formulations at low or high shear mixing. It is also further desirable that such a modifier is stable under prolonged mixing in a paint kitchen.

SUMMARY
The present invention is directed to a modifier for improving the surface properties of a coating composition. The said modifier comprises of inorganic nanoparticles having at least one reactive functional group covalently bonded to a polymeric surface modifying agent, wherein the polymeric surface modifying agent is an organohydrosiloxane having at least one [—HSiR—O—] unit, each R being independently an alkyl group having 1 to 4 carbon atoms.

The present invention also discloses a coating composition comprising aforesaid modifier.

BRIEF DESCRIPTION OF DRAWINGS

Figures 1a and 1b illustrate Proton nuclear magnetic resonance (1H NMR) analysis of the sample 6 prepared in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION
To promote an understanding of the principles of the invention, reference will be made to the embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation of scope of the invention is thereby intended, such alterations and further modifications in the described product and such further applications of the principles of the inventions as disclosed therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

The present disclosure generally relates to a modifier for improving the surface properties of a coating composition. More particularly, the modifier of the present disclosure comprises of inorganic nanoparticles having at least one reactive functional group covalently bonded to a polymeric surface modifying agent, wherein the polymeric surface modifying agent is an organohydrosiloxane having at least one [—HSiR—O—] unit, each R being independently an alkyl group having 1 to 4 carbon atoms.

The hydride groups present on organohydrosiloxane reacts with the reactive functional groups present on the inorganic nanoparticles to obtain covalently bonded polysiloxane network with inorganic nanoparticles, the modifier disclosed herein.
In accordance with an aspect, the use of organohydrosiloxane based polymeric surface modifying agent introduces softness in the resultant coating and thus prevents the brittleness of the final coating. Due to the presence of organohydrosiloxane there is increase in flexibility of the cured coating and reduction in the crater formation on the surface when blended with 1K/2K coating system. Also, there is increase in homogeneity of the coating composition on the surface. Further, the absence of true chemical bond between the inorganic nanoparticles and the coating matrix leads to migration of inorganic nanoparticles towards the surface of the coating and hence renders glass like properties to the coating surface thereby providing improved abrasion resistance, mar resistance and scratch resistance to the coating. The inorganic nanoparticles migrate towards the coating surface also because of low bulk density. Migration of inorganic nanoparticles to surface of coating during curing provides further advantages such as lesser amount of inorganic nanoparticles in the range of 1 to 10 wt% based on total weight in the formulation is required to achieve the desired surface properties. Further, the inorganic nanoparticles present on surface of coating provide anchoring points thereby allowing ability to recoat the surface with the coating composition.

In accordance with an embodiment, said organohydrosiloxane has a general Formula I:

(I)

wherein R1, R2, R3, R4, R5, R6 and R7 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen, and
n =5 to 46.
In accordance with an embodiment, said organohydrosiloxane having Formula I has molecular weight in a range of 1000 to 3500 Da, and preferably 1400 to 3200 Da.
In accordance with an embodiment, the organohydrosiloxane has a general Formula II:

II

wherein R1, R2, R3, R4, R6, R7, R8, R9 and R10 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen,
m=2-14, and
n=1-7.
In accordance with an embodiment, said organohydrosiloxane having Formula II has a molecular weight in a range of 700 to 2500 Da, and preferably 900-2000 Da.
Said organohydrosiloxane may be prepared by any known method or may be obtained from any commercial source.
In accordance with an embodiment, the molar ratio of the inorganic nanoparticles and the organohydrosiloxane is in a range of 35 to 175 and preferably 65 to 135. In accordance with a related embodiment, the amount of inorganic nanoparticles in the modifier of the present invention is in the range of 15-35 wt% based on total weight.
In accordance with an embodiment, the inorganic nanoparticles are selected from a group comprising of silica, alumina, titania, zirconia, clay and mixtures thereof. In accordance with a preferred embodiment, silica nanoparticles are used. Further, the silica nanoparticles may be present either in powder or dispersed form. In accordance with a related embodiment, silica nanoparticles may be obtained from commercial source. Preferably, sols of silica are used. It could be aqueous based silica sol (aquasol) or any polar/ non-polar solvent based silica sol. The polar solvent may be but not restricted to any alcohol and non-polar solvent. The non-polar solvent may be but not restricted to butyl acetate, methoxy propyl acetate, heptanone, methyl ethyl ketone. In accordance with a related embodiment, silica nanoparticles have a particle size in the range of 1- 60 nm and preferably 5-20 nm. The pH of the aqueous silica sol could be acidic or basic or neutral where the silica loading could be from 15 to 50 wt% with a particle size distribution from 4 nm to 4 micron. The pH of aqueous based sol which is used in the present invention may range from 2 to 4 with particle size distribution (PSD) of 5 to 60 nm and silica loading of 15 to 35 wt%. The alcohol based silica sol could have pH 3 to 4, with PSD of 5 to 60 nm and silica loading of 15 to 35 wt%. The non-polar solvent based silica sol may have a PSD of 5 to 60 nm with silica loading 15 to 35 wt%. Alternatively, silica nanoparticles may be obtained by controlled hydrolysis of tetraethylorthosilicate, methyl trimethoxy silane, ethyl trimethoxy silane or any other suitable derivative of siloxane or silicate compounds in presence of any of acid, base and water.
In accordance with an embodiment, the reactive functional group on the inorganic nanoparticles is hydroxyl group. In accordance with an embodiment, sol containing inorganic nanoparticles having free hydroxyl groups is used. In accordance with a preferred embodiment, the hydroxyl groups on the inorganic nanoparticles are made hydrophobic by partial substitution of -OH group with alkoxy group. This can be done with organic solvents such as ethanol, butanol etc. Any known technique may be used to alkylate the inorganic nanoparticles.
In accordance with an embodiment, the modifier further comprises of one or both of a pigment dispersing agent and a surface tension modifier agent. In accordance with an embodiment, said pigment dispersing agent and/ or surface tension modifier agent may be selected from a group consisting of high or low molecular weight copolymer/ homopolymer of polyacrylate, silicone, polyamide and mixture thereof.
In accordance with an embodiment, the pigment dispersing agent may be added in an amount ranging between 0.1-10 wt% with respect to the total weight of the modifier. In accordance with an embodiment, any surface tension modifier agent can be added to adjust the surface tension of the coating formulation. In accordance with an embodiment, said surface tension modifier agent is selected from a group consisting of polysiloxane or polyacrylate or any silicone free material. In accordance with a specific embodiment, the surface tension modifier agent can be a homopolymer, copolymer or block copolymer of polysiloxane and polyacrylate consisting of polyester, polyether or polyacrylate. The surface tension modifier agent may be added in an amount ranging between 0.1 to 10 wt% with respect to the total weight of solid silica. The surface tension modifying agent can be 100 wt% solid or could be in solvent compatible with the coating composition. The surface tension modifying agent can be used alone or in combination with other flow and leveling agents.
The modifier as described in the present disclosure may be used with any thermally cured radiation curable 1K / 2K coating compositions. In accordance with an embodiment, the modifier may be used as a filler for any polypropylene, polyurethane, nylon, PBT, polyimide, polyether ketone, polyethylene terephthalate, PPT, polyesters, polyamide, polyacrylate, polyether, polysulphone based polymer systems. The coating composition may further comprise certain additives such as UV-absorbers, defoamers, plasticizers, adhesion promoters, light stabilizers, anti-oxidants, colouring agent, flow controllers/ enhancers, catalysts, wetting agents, leveling agents, sag control agent, organic solvent etc.
A process of preparing aforesaid modifier is also disclosed. Said process comprises of adding to a dispersion of inorganic nanoparticles, afore-said polymeric surface modifying agent in the desired molar ratio, followed by heating the reaction mixture in the presence of dibutyltin dilaurate (DBTDL) at an elevated temperature in the range of 90-150 oC and preferably in the range of 115 to 125 oC for a predetermined time period in a range of 1-4 hours, and preferably 2 hours. Herein, the afore-mentioned dispersion of inorganic nanoparticles is prepared by butylation of inorganic nanoparticles (in aqueous phase), followed by dispersion in a desired non-polar organic solvent. The butylation is carried out using a process described in Ruiz et. al. J. Phys. Chem. C, 2007, 111 (21), pp 7623–7628.
In accordance with an embodiement, the non-polar organic solvents may include but is not limited to xylene, butyl acetate, methoxy propyl acetate, ethoxypropyl acetate, heptanone, and aliphatic hydrocarbon.
The modifier once prepared may be dispersed in solvents for storage and transportation.
In accordance with an embodiment, a method of preparing the coating composition comprising the modifier described above is also disclosed. The said method comprises of adding to the coating composition, the modifier of the present invention in a predetermined quantity. In accordance with a preferred embodiment, the amount of the modifier added to the coating composition is in the range of 1-10 % by weight based on the total weight.

The coating composition according to the invention may be used for coating automotive parts, various other substrates such as wood, metal, alloys, ceramic and plastic. The coating composition may be any thermally, radiation curable 1K / 2K coating compositions. These coating compositions could be clear coat without any colorant or could be colored.

Any known method of coating the coating composition prepared in accordance with the present invention may be used. These include, for example, spray coating, dip coating, roll coating, curtain coating, and the like. Further, various methods of curing may be used, however, heat curing is preferred. The curing time may vary depending on the substrate, the coating formulation, ambient conditions etc.

The coating could be applied by applying primer, followed by base coat and clear top coat after providing sufficient flash off time between each coat which is usually in the range of 5 to 15 minutes. In accordance with an alternate embodiment, base coat can be prebaked prior to applying top coat which is then baked again.

In accordance with an embodiment, thermoset based coating compositions can be cured by any known method. In accordance with an embodiment, curing is done by baking at temperature ranging between 60 to 200 °C and preferably between 80 to 200 °C. In accordance with yet another embodiment, 2K polyol-isocyanate based coating compositions are cured at temperature ranging between 60 to 120 °C. Similarly, for 1K resin system baking is done at temperature ranging between 120 to 160 °C.

Examples
The following examples are provided to explain and illustrate the preferred embodiments of the process of the present invention and do not in any way limit the scope of the invention as described and claimed:

Example 1: Synthesis of modifier in accordance with the present disclosure

Sample 1: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a round bottom (RB) flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask 300 grams of isopropanol (Molychem) and 200 grams of n-butanol (SD-fine chemical Ltd.) was added. The solution was evaporated using rotavapor at 30 °C under reduced pressure until the amount of the solution in the RB flask became 223 grams. To this 150 grams of methoxy propyl acetate was added and the mixture was heated to 90 oC and maintained for one hour. The solution was concentrated to 273 grams. To this around 4 grams of polymethylhydrosiloxane, trimethylsiloxy terminated (PMHS), molecular weight 1400 to 3200, and 0.086 g of dibutyl tin dilaurate (DBTDL,95%, Aldrich) were added and the reaction mass was heated to 135 °C (reflux temperature inside the flux 115-120 °C) for 2 hours. Finally, the solution was concentrated at 55 °C to 100 grams. The organosol was found to be stable at room temperature over a period of 6 months.
Further, solid silica loading in the modifier was found to be 23wt%. The viscosity was found to be 2.9 cPs at 25 °C using Brookfield viscometer.
Sample 2: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask were added 300 grams of isopropanol (Molychem) and 200 grams of butanol (SD-fine chemical Ltd.). The solution was evaporated using rotavapor at 30 oC under reduced pressure until the amount of the solution in the RB becomes 223 grams. To this 150 grams of methoxypropyl acetate (Sigma Aldrich) was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 4 grams of PMHS and 0.086 g of DBTDL (95%, Aldrich) was added and the reaction was heated to 135 °C for (reflux temperature inside the flux 115-120 °C) 2 hours. Finally the solution was concentrated at 55 oC to 98 grams. To this solution around 2.3 grams of DISPERBYK-168 was added. The dispersion of silica sol was found to be stable for more than 6 months at room temperature.
Solid silica loading in the modifier was found to be 23wt%. The viscosity was found to be 3 cPs at 25 °C using Brookfield viscometer.

Sample 3: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask were added 300 grams of isopropanol (Molychem) and 200 grams of butanol (SD-fine chemical Ltd.). The solution was evaporated using rotavapor at 30oC under reduced pressure until the amount of the solution in the RB becomes 223 grams. To this 150 grams of methoxypropyl acetate (Sigma Aldrich) was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 4 grams of PMHS and 0.086 g of DBTDL (95%, Aldrich) was added and the reaction was heated to 135 °C for (reflux temperature inside the flux 115-120 °C) 2 hours. Finally the solution was concentrated at 55 oC to 96 grams. To this solution around 2.3 grams of DISPERBYK-168 was added and also around 2.3 grams of BYK 307 was added. The dispersion of silica sol was found to be stable for more than 6 months at room temperature.
Solid silica loading in the modifier was found to be 23wt%. The viscosity was found to be 3 cPs at 25 °C using Brookfield viscometer.
Sample 4: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask were added 300 grams of isopropanol (Molychem) and 200 grams of butanol (SD-fine chemical Ltd.). The solution was evaporated using rotavapor at 30oC until the amount of the solution in the RB becomes 223 grams. To this 150 grams of methoxy propyl acetate was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 4 grams of PMHS and 0.086 grams of DBTDL (95%, Aldrich) were added and the reaction was heated to 135 °C (reflux temperature inside the flux 115-120 °C) for 2 hours. Finally, the solution was concentrated at 55 oC to 87 grams. To this solution around 2.3 grams of DISPERBYK-168 was added and also around 10 grams of BYK 307 was added.
Solid silica loading in the modifier was found to be 23 wt%. The viscosity was found to be 3.7 cPs at 25 °C using Brookfield viscometer.
Sample 5: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask 300 grams of isopropanol (Molychem) and 200 grams of n-butanol (SD-fine chemical Ltd.) was added. The solution was evaporated using rotavapor at 30oC under reduced pressure until the amount of the solution in the RB becomes 223 grams. To this 150 grams of methoxy propyl acetate was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 8 grams of PMHS and 0.086 g of DBTDL (95%, Aldrich) was added and the reaction was heated to 135 °C (reflux temperature inside the flux 115-120 °C) for 2 hours. Finally the solution was concentrated at 55 oC to 83 grams. To this solution around 2.3 grams of DISPERBYK-168 was added and also 1.38 grams of BYK-307 was added.
Solid silica loading in the modifier was found to be 28 wt%. The viscosity was found to be 5.52 cPs at 25 °C using Brookfield viscometer.
Sample 6: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask 300 grams of isopropanol (Molychem) and 200 grams of n-butanol (SD-fine chemical Ltd.) was added. The solution was evaporated using rotavapor at 30oC under reduced pressure until the amount of the solution in the RB becomes 223g. To this 150 grams of methoxy propyl acetate was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 8 grams of PMHS and 0.086 grams of DBTDL (95%, Aldrich) was added and the reaction was heated to 135 °C (reflux temperature inside the flux 115-120 °C) for 2 hours. Finally, the solution was concentrated at 55 oC to 83 grams. 1H NMR analysis of the sample in Figures 1a and 1b shows that PMHS reacts with the silica to form Si-O-Si linkages.
To this solution around 2.3 grams of DISPERBYK-168 was added and also around 1.61 grams of BYK-307 was added. The dispersion of silica sol was found to be stable for more than 6 months at room temperature.
Solid silica loading in the modifier was found to be 28 wt%. The viscosity was found to be 5.57 cPs at 25 °C using Brookfield viscometer.
Sample 7: About 100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask were added 300 grams of isopropanol (Molychem) and 200 grams of butanol (SD-fine chemical Ltd.). The solution was evaporated using rotavapor at 30oC under reduced pressure until the amount of the solution in the RB becomes 223 grams. To this 150 grams of methoxy propyl acetate was added to the RB flask and heated at 90 oC for one hour. The solution was concentrated to 273 grams. To this around 8 grams of PMHS and 0.086 grams of DBTDL (95%, Aldrich) was added and the reaction was heated to 135 °C (reflux temperature inside the flux 115-120 °C) for 2 hours. Finally, the solution was concentrated at 55 oC to 83 grams. To this solution around 2.3 grams of DISPERBYK-168 was added and also around 1.3 grams of BYK 307 was added.
Solid silica loading in the modifier was found to be 28 wt%. The viscosity was found to be 5.52 cPs at 25 °C using Brookfield viscometer.
Comparative Sample 1(including silica without polymeric surface modifying agent)
100 grams of aqueous silica sol (snowtex-O, PH-2-4, 23 wt % sillica, Nissan Chemical America corporation) was taken in a RB flask attached with a condenser. The assembly was maintained under N2 atmosphere. To the RB flask 300 grams of isopropanol (Molychem) and 200 grams of n-butanol (SD-fine chemical Ltd.) was added. The solution was distilled using rotavapor at 30 oC until the amount of the solution in the RB flask became 223 grams. To this 150 grams of methoxy propyl acetate was added and heated at 90 oC for one hour. The solution was concentrated to 273 grams.
Solid silica loading in the modifier was found to be 9.8 wt%.
Comparative Sample 2 (including only polymeric surface modifying agent without silica)
To the clear coat thermosetting acrylate (TSA) system only PMHS was added. The mixture was diluted with C9 solvent. Coating was drawn on glass plate using 60 micron applicator bar. The coating turns hazy upon curing.

Test panel preparation:
Plastic panels made of ABS and MS panel surface pretreated obtained from Q-Lab and tin plate with dimension 14.5 cm /7.5 cm and A4 size panel was surface cleaned with appropriate cleaning solvent such as IPA, ethyl acetate or xylene.
All the coatings were applied by spray technique.
The base coat was applied on the test panels at dry film thickness of 15-20 micron, followed by 7 minutes flash off. The clear coat was then applied at dry film thickness of 35- 45 micron followed by 15 minutes flash off. Base coat and clear coat were applied by wet/wet basis or base coat can be prebaked and followed by application of clear coat.
The coating was baked at 140 °C for 30 minutes. For acrylic melamine based resin system scratch test was done after 1 h. Polyurethane based coating was applied on ABS panel as well as on tin plate and baked at 80°C for 30 minutes and 20 minutes respectively. Abrasion resistance test was carried out at interval of 24, 48 and 72 hours.
Performance Analysis method:
Abrasion resistance of the coated test panel was measured by measuring the initial gloss at 20° using Sheen trigloss meter. The baked coated panels were cleaned from dust using soft cloth and then subjected to scratch testing by linearly drawing the panels with a weighted 9 micron polish paper, obtained from 3M Company. 1.5 kg hammer was fitted with 9 micron paper and the panels were subjected to 20 double rubs linearly. The rubbed portion was cleaned and the gloss was measured again at 20°.
Percent of initial gloss retention was measured by the following equation:
100% x scratched gloss/initial gloss
Example 2: Testing on thermosetting acrylate clear coat system- Various samples of the thermosetting acrylate clear coat coating composition were prepared by adding the modifiers as prepared in samples 1 to 7 and blank samples 1 and 2 to study the effect of the modifier on the properties of the cured film. The modifier was stirred in the coating formulation at 1000 rpm for 15 minutes. The thermosetting acrylate clear coat formulation was diluted with C9 solvent in the ratio of 4:1 prior to application. Before application the coating formulation was filtered using nylon 400 mesh filter.
Ingredients used for thermosetting acrylate clear coat system:
Thermosetting acrylate 53.7 g
Melamineformaldehyde resin 22.7g
Setalux resin 5.0 g
Byk 390 0.2 g
Tinuvin 1130 0.7g
50% solution of disperlon 0.2 g
Butanol 3.0 g
Solvent C9 0.3g
Diglycol acetate 1.0 g

Table 1: Results of the abrasion resistance for thermosetting acrylate clear coat system
Serial number Sample initial gloss at 20° Gloss after 20 double rubs at 20° % Gloss retention at 20 °
1 Standard (thermosetting acrylate clear coat formulation without modifier) 89.22 45.32 50.8
2 Standard with 3% modifier of Sample 1 94.8 90.06 95
3 Standard with 3% modifier of Sample 2 92.3 87.5 94.7
4 Standard with 3% modifier of Sample 3 92.75 75.7 81.6
5 Standard with 6% modifier of Sample 3 90.1 81.4 91.3
6 Standard with 3% modifier of Sample 3 (16h stirring) 90.3 73.4 81.3
7 Standard with 3% modifier of Sample 3 (Storage stability for 1 month at 50 °C) 88 70 80.5
8 Standard with 3% modifier of Sample 4 91.3 61.7 67
9 Standard with 3% modifier of Sample 5 90.43 82.2 90.9
10 Standard with 3% modifier of Sample 6 90.2 82 90
11 Standard with 3% modifier of Sample 6 (Storage stability for 1 month at 60 °C) 89 73.4 83
12 Standard with 3% modifier of Sample 6 (stirring for 16 hrs) 89.4 73 82
13 Standard with 3% modifier of Sample 7 89.9 80.66 89.7
14 Standard with 3% modifier of Comparative Sample 1 Hazy film -- --
15 Standard with 3% modifier of Comparative Sample 2 Hazy film -- --
16 Standard with 3% modifier of Sample 6 (stirred by hand) 88.7 69.3 79

Example 3: Testing on polyacrylate polyol and isocynate (2k) resins systems:
Metallic base coat:Base coat (blazing silver colour) contains mixture of two acrylic polyol resins with solid content of 54.5%. The formulation also contains wax dispersion, cellulose acetate butyrate and anti-settling additives. Hexamethylenediisocyanate (HMDI) was used as crosslinking agent and thinner used was a mixture of xylene, solvent C9 and butyl acetate (55:30:15).

Clear top coat formulation:
The top clear coat was prepared using the following materials:
Polyacrylatepolyol : 73.2 g
Defoamer (BYK): 0.09g
HALS (BASF) : 0.37 g UV absorber (BASF) : 0.73g
Glycol ether ester solvent : 11.0 g
Butyl diglycolacetate : 1.83g
Duranate 22A/75PX (NCO content 16.5% and solid content 75%) as catalyst used stoichiometrically
Silicon flow additive (BYK): 0.094 g;
Modaflow Acrylic flow additive (Cytec): 0.013 g
Modifier of Example 6 : 3.0 g;
DBTDL (95%, Aldrich) : 0.009 g

Application of 2K coating system to Acrylonitrile Butadiene Styrene (ABS) and metal sheet (MS) panels

ABS and metallic panels were cleaned with iso-propanol and allowed to dry. The 2K polyurethane metallic base coat was applied on both the panels to get the DFT of 20 to 25 microns. The coating was given flash off time of 10 minutes. Clear top coat was sprayed on the panels to achieve DFT of 35 to 40 microns. After additional flash off time of 10 minutes, the panels were baked at 80 oC for 30 minutes.

Various samples of the above coating composition were prepared to determine and compare the effect of the modifier of the present invention on various properties of the resulting coating composition.

Table 2: Result of abrasion resistance analysis for 2K PU system on metal plate
Sample Name Polyacrylate polyol and isocynate (2k) system without modifier Polyacrylate polyol and isocynate (2k) system with 3% modifier of Example 6
Gloss at 20 0 60 0 20 0 60 0
Initial gloss 86.33 95.7 85.96 95.7
Gloss after 24 hrs 14.66 42.7 38 67.6
% Retention 18 45 45 69
Gloss after 48 hrs 13.6 41.9 39.4 70.9
% Retention 16 44 46 75
Gloss after 72 hrs 15.6 43.6 47.9 77.4
% Retention 15.6 46 58 81

Table 3: Results of abrasion resistance for 2K PU system on ABS panel
Sample Name Polyacrylate polyol and isocynate (2k) system without modifier Polyacrylate polyol and isocynate (2k) system with 3% modifier of Example 6
Gloss at 20° 20°
Initial gloss 82.3 84
Gloss after 24 hrs 16.6 52.9
% Retention 20 63

Example 4: Effect of the modifier on the properties of the pigmented coating composition

Testing with pigmented top coat system:
Sample of the coating composition was prepared to determine and compare the effect of the modifier of the present invention on various properties of the pigmented green thermosetting acrylate polyol and isocyanate 2K system. The system was diluted using thinner mixture of xylene, C9, butyl acetate mixed in a ratio of 50 : 20 : 30 by weight. Result of abrasion resistance of sample is illustrated below:
Table 4: Result of abrasion resistance of sample
Sample Name Pigmented polyacrylate polyol and isocynate (2k) system without modifier Pigmented polyacrylate polyol and isocynate (2k) system with 3% modifier of Example 6
Gloss at 20° 20°
Initial gloss 86 87.4
Gloss after 24 hrs 53 73
% Retention 43 84

SPECIFIC EMBODIMENTS ARE STATED BELOW

A modifier for a coating composition, the modifier comprising inorganic nanoparticles having at least one reactive functional group covalently bonded to a polymeric surface modifying agent, wherein the polymeric surface modifying agent is an organohydrosiloxane having at least one [—HSiR—O—] unit, each R being independently an alkyl group having 1 to 4 carbon atoms.

Such a modifier(s), wherein the organohydrosiloxane has a general formula I:

(I)

wherein R1, R2, R3, R4, R5, R6 and R7 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen, and
n =5 to 46,
such that the organohydrosiloxane has a molecular weight in a range of 1000 to 3500 Da.
Such a modifier(s), wherein the organohydrosiloxane has a general Formula II:

(II)

wherein R1, R2, R3, R4, R6, R7, R8, R9 and R10 are independently an alkyl group having 1- 4 carbon atoms,
X is a reactive hydrogen,
m=2-14, and
n=1-7
such that the organohydrosiloxane has a molecular weight in a range of 700 to 2500 Da.
Such a modifier(s), wherein the molar ratio of the inorganic nanoparticles to the organohydrosiloxane is in a range of 65 to 155.

Such a modifier(s), wherein the inorganic nanoparticles are selected from a group consisting of silica, alumina, titania, zirconia, clay and mixtures thereof.

Such a modifier(s), wherein the reactive functional group is hydroxyl group.

Such a modifier(s), further comprising a dispersing agent, a surface tension modifying agent and a mixture thereof.

A coating composition comprising afore-said modifier.

INDUSTRIAL APPLICABILITY

The above disclosed modifier can be used in 1K and 2K TSA, PU and other coating systems. Using low amount of modifier at = 6 wt% improves abrasion resistance property of the coating composition.
The modifier can be also used in UV or thermally curable resin system to obtain remarkable surface properties. The modifier remains stable in coating composition under high and low speed stirring e.g. mixing at 100 to 1000 rpm or by simple hand mixing. Also, the modifier while stirring at = 600rpm in commercial coating compositions continuously for over a period of more than 16 hours does not alter its performance. Further, the modifier shows good storage stability.
Addition of modifier results in obtaining coating compositions having desired surface properties such as improved abrasion resistance, mar resistance, high gloss retainability without affecting recoatability. The coating obtained by using this modifier also helps in reducing haziness and crater formation in the final coating which is clearly not acceptable in the coating industries.
The process of preparing the modifier of the present disclosure is simple and easy to carry out.