Claims:We Claim:

1. Anti-graffiticoating composition thereofcomprising
A) 55-80 wt.% of polyester resin having hydroxyl value in the range of 30-130 mg KOH/gm, weight average molecular weight Mn in the range of 3000 to 5000 and glass transition temperature between 40-68 °C;
B) 15-35 wt.% of aliphatic/cycloaliphatic/aromatic blocked hardener;
C) 0.5 to 4 wt.% of additive including siloxane based surface modifier that is -OH functionalized and polyester modified; and
D) 10-20 wt.% pigments and extenders.

2. The Anti-graffiti coating composition as claimed in claim 1 wherein said polyester resin is comprised of reactants including neopentyl glycol (20- 45 wt%), ethylene glycol (0-7 wt%), diethylene glycol (0-5 wt.%), MP diol (1-15 wt%), butyl ethyl propanediol (1-3 wt%), hexane diol (1-3 wt.%) trimethylolpropane (1-15 wt.%), adipic acid (1-3 wt%), terephthalic acid (30-65 wt.%), isophthalic acid (1-20 wt.%), hexahydro phthalic anhydride (1-5 wt.%), pentaerythritol (1-3 wt.%), cyclohexanedicarboxylic acid (1-4 wt.%), cyclohexanedimethanol (1-4 wt.%), having equivalent ratio of polyols to polyacids between 1.10-1.28.

3. The Anti-graffiticoating composition as claimed in claims 1 or 2 wherein said aliphatic/cycloaliphatic/aromatic blocked hardeneror mixtures thereof selected from diisocyanates, polyisocyanates and urethdiones, as blocked compounds wherein diisocyanates and polyisocyanates includeshexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate,toluylene diisocyanate, cyclohexane diisocyanate,trimethylhexane diisocyanate, tetramethylenexylylene diisocyanate,cyclohexanedimethylene diisocyanate, dicyclohexylmethane diisocyanateor the trimerization products, for example, aliphatic diisocyanate based isocyanurates or mixtures thereof;aromatic diisocyanate including tolylene diisocyanate (TDI), diphenylalkyl diisocyanates or mixtures thereof, wherein the diisocyanates, polyisocyanates and urethdiones are employed as blocked diisocyanates, polyisocyanates and urethdiones blocked with monoalcohols, glycol ethers, ketoximes, lactams, malonic acid esters, acetoacetic acid esters, for example, ethylene glycol monobutyl ether, butanone oxime, phenol, ethyl acetoacetate, dimethylpyrazole or caprolactam.

4. The Anti-graffiti coating composition as claimed in claims1-3 wherein said additive include siloxane based surface modifier that is -OH functionalized and polyester modified, degassing agent.

5. The Anti-graffiti coating composition as claimed in claims 1-4 wherein saidsiloxane based surface modifier is -OH functionalized and polyester modified, including functional modified polysiloxane, solid supported polysiloxanes including polyester modified-hydroxyl functional polysiloxanes preferably polyester modified-hydroxyl functional polysiloxanes.

6. The Anti-graffiti coating composition as claimed in claims 1-5 wherein said degassing agent includesbenzoin and/or modified wax, pigments selected fromtransparent, color-imparting and/or special effect-imparting pigments and/or fillers (extenders), inorganic or organic color-imparting pigments includes carbon black, iron oxide, titanium dioxide, micronized titanium dioxide, phthalocyanine, and azopigments, pigments whereas special effect-imparting pigments are metal pigments, made from copper, aluminum, or other metals, interference pigments including metal oxide coated metal pigments and coated mica and usable extenders includes aluminum silicate, barium sulfate, silicon dioxide, magnesium carbonate, calcium carbonate, and micronized dolomite.

7. A method of preparinganti-graffiticoating composition as claimed in claims 1-6 comprising the steps of providing the following ingredients
a. providing 55-80 wt.% of polyester resinhaving hydroxyl value 30-130 mg KOH/gm;
b. providing 15-40 wt.% of aliphatic/cycloaliphatic/aromatic blocked hardener;
c. providing 0.5 to 4 wt.% of additive including siloxane based surface modifiers;
d. providing 10-20 wt.% pigments, extenders and blending and selectively extruding to attain said coating composition thereof.

8. The method of preparing anti-graffiti coating composition as claimed in claim 7 wherein the steps of providing polyester resin having hydroxyl value 30-130 mg KOH/gm preferably with select melt viscosity of polyesterbetween 40-70 poise at 200°C is based on synthesis of polyester resin by involving the ingredients ofneopentyl glycol (20- 45 wt%), ethylene glycol (0-7 wt%), diethylene glycol (0-5 wt%), MP diol (1-15 wt%), butyl ethyl propanediol (1-3 wt%), hexane diol (1-3 wt%) trimethylolpropane (1-15 wt%), adipic acid (1-3 wt%), terephthalic acid (30-65 wt%), isophthalic acid (1-20 wt%), hexahydro phthalic anhydride (1-5 wt%), pentaerythritol (1-3 wt%), cyclohexanedicarboxylic acid (1-4 wt%), cyclohexanedimethanol (1-4 wt%) maintaining equivalent ratio of polyols to polyacids between 1.10-1.28.

9. The method of preparing anti-graffiti coating composition as claimed in claims 7 or 8 wherein the steps includes
i. Mixing saidingredients of the composition and extruding in an extruder at 110-120°C and at RPM of 250-300 to achieve proper dispersion.;
ii. Cooling down the melt-mixed formulation followed by grinding;
iii. Classifying the resulted powder material from step (ii)with 150 mesh size screens to provide for classified powder;

iv. Applying said classified powder by electrostatic spray gun to one side of the aluminum or stainless steel panel;
v. Curing at 180-210 deg C for 25-10 min to provide dry film with a thickness of 70-80 um having anti-graffiti attributes.

Dated this the 30th day of March, 2022 Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
IN/PA-199
, Description:Field of the Invention:
The present invention relates to powder polyester andanti-graffiticoating composition thereof. More particularly,said anti-graffiti powder coating compositionis devoid of multiple polymers/polyesters or HDPE.

Background of the Invention
The term "graffiti" means any unwanted painting, drawing, lettering or other marking formed on a surface. Graffiti is typically applied using paints, usually applied by spray cans, or markers. The paints are usually oil-based paints including enamels, epoxies, lacquers and urethanes and markers are typically color markers having pigmented dyes with fast drying solvents.
Such markings/paintings are particularly troublesomebecause they are often very difficult to remove from thesurfaces on which they have been applied. Thus, painted surfaces often must be repainted to cover up the markingsand sometimes must be even stripped and then repainted.For example, graffiti often is applied with paint similar tothat on the surface. Removal of the graffiti paint by abrasionor with a solvent therefore is impractical because it typicallyresults in removal of at least a portion of the underlyingpaint. Unpainted surfaces,sometimes must be sandblasted toremove the markings.Another solution is to protect the wall with high security measures and constant vigil or to make fencing to protect the wall from intruders. However, such solutions are expensive and labor intensive.
Other option may include coating the surface ofthe article that would serve as a barrier to permit easyremoval of such markings. Or coating the surface that maybe resistant to graffiti. The phenomenonhas prompted the coatings industry to individuate new solutionsto limit the high costs related to the removal ofgraffiti [US 2004/0162381 A1]. The development of specific anti-graffiti coatings showeda relevant growth only in recent years.
The anti-graffiti coatings formulations can be broadly classified as solvent based coating and powder coating. Powder coating is a zero VOC (volatile organic components) compared to solvent based system. During the application of powder, some percent of powder does not deposit on the substrate rather it ends up depositing on walls or base of application booth. That powder can be collected and reused. In a way there is minimum loss of material. Solvent based system can be three coat, single bake system where top coat which exhibit anti-graffiti property is a clear coat. Whereas for powder coating similar kind of property can be achieved in a single step environment friendly pigmented system.

Epoxy, polyester and acrylic resin binders are well-known for the use in thermal curable powder coating compositions. For example, hydroxyl functional polyesters are curable with isocyanates to result in polyurethane powder coatings, see D. Bates, The Science of Powder Coatings, Volume 1, London, 1990, page 56, 276-277, 282.Combinations of different resin binders and curing agents are investigated to receive specific desired properties of the coatings on different substrate surfaces.
For anti-graffiti powder coating composition major breakthrough was provided by US20090018263A1 which comprises
(A) 30 to 80 wt % of a mixture of at least one polyester resin A having a hydroxyl number in the range of 30 to 60 mg KOH/g, a weight average molar mass Mn in a range of 3100 to 5000 and a glass transition temperature Tg of 40 to 60° C. and at least one polyester resin B having a hydroxyl number in the range of 250 to 350 mg KOH/g, a weight average molar mass Mn in a range of 2000 to 3000,
(B) 10 to 40 wt % of at least one hardeners diisocyanates, polyisocyanates or urethdiones, and
(C) 0.01 to 40 wt % of at least one coating additive, pigment and/or filler.
The powder coating composition provide very good anti-graffiti performance over long time period and good coating properties.Extensive efforts have been made for an alternative composition/formulation providing similar benefits. Few related prior arts are as follows:

US2004/0162381A1disclosesan anti-graffiti composition comprised of a polymer and mineral oil. Said anti-graffiti composition composed:substantially of polymer; andincluding 0.01% to about 10% by weight of a mineral oil, the mineral oil being present in an amount to impart anti-graffiti properties to the compositionwherein polymer is a polyolefin compound more preferably HDPE.

US8968876B2is directed to coating compositions that may be cured to provide a coating with enhanced resistance to the stains and marks caused by the ink and colorants in pens, markers and the like. Said anti-graffiti coatingcomposition, comprises:
a functionalized epoxy resin wherein the epoxy resin comprises at least one of (meth)acryl or acetoacetyl functionality;
a (meth)acryl functional compound;
a silicone compound with (meth)acryl functionality;
a non-silica organic flatting agent; andmetal particles.

US7501472B2 concerns about an aqueous fluoromodified polyurethane system for one- or two-component anti-graffiti and anti-soiling coatings which follows the steps of (a) preparing a binder component based on an aqueous solution or dispersion of optionally hydroxy- and/or amino-functional oligourethanes and/or polyurethanes having fluorinated side chains, and, optionally, (b) subsequently reacting the binder component with a crosslinker.

US7737195B2 reveals anon-sacrificial, penetrating, anti-graffiti coating consisting essentially of the combination of alkali metal silicate, for example potassium, lithium or sodium silicate, deionized water, ethylene-glycol colloidal silica, aminopropyl oxysilane, fluorinated polyurethane, and alkali metal methyl siliconate, such as potassium, lithium or sodium siliconate.

CN110669420Aprovidesa doodling-resistant polyurethane powder coating which comprises hydroxyl-terminated polyester resin, blocked polyisocyanate, polyvinylidene fluoride, rutile titanium dioxide barium sulfate, leveling agent, wetting accelerator, benzoin, pigment carbon black, phthalocyanine blue and iron oxide yellow. After the powder coating is coated into a film, the surface hardness is high (can reach 4H), the surface is difficult to damage in the repeated wiping process, easy to clean and shows good anti-graffiti effect.

TargetedAnti-graffiti Multifunctional powder coatingof CN110003782A is made of polyurethane resin (HV:36-40), polyurethane resin (HV:280-310) andnano material and nano silica, coarse structure is constructed in coating surface using hydrophobic material nano silica, provides hydrophobic oleophobic, anti-graffiti powdery paints.

Powder coating comprisingPowder lacquer (A), which comprises:two polyols- one amorphous and other crystalline in a selective ratio along with an unblocked micronized polyisocyanate based on cycloaliphatic diisocyanate (B), and (C) further auxiliary material and additive from the powder lacquer technology is disclosed by EP2159238A1.

US20090155462A1relates to a powder coating composition comprising(A) at least one hydroxyl functional polyester resin binder, and(B) at least one polyurethane resin as cross-linking agent containing blocked isocyanate groups,wherein said hydroxyl functional polyester resin binder (A) and polyurethane resin (B) both having a melting temperature of 60 to 180° C., in particular, 60 to 160° C. and the polyester resin binder (A) has a hydroxyl value of 30 to 300 mg KOH/g and a number-average molar mass between 500 to 5000.The powder coating composition according to the advancement provides thin films and high flexibility in combination with excellent mechanical properties of the coatings.

CN109651950Ateachesanti-graffiti powdery paints, including of polyester resin containing terminal hydroxy group, blocked isocyanate, 2- hydroxyl -2- phenyl acetophenone, modified waxes, pigment and bloom barium sulfate. Wherein, the hydroxyl value of the polyester resin containing terminal hydroxy group is 190~210mgKOH/g. The anti-graffiti powdery paints has excellent stain resistant performance (hydrophobicity and oleophobic property), scraping and wiping resistance performance and stronger hardness, and anti-graffiti property is strong.

US20070142517A1reveals a dry-erase surface composition comprising a mixture of:
a. an alkyd resin and urethane alkyd base component; and
b. substantially equal parts by percent weight of hydroxyl alkyl polydimethylsiloxane and polytetrafluoroethyleneand method of applyingwherein an endless number of colors can be produced through the addition of the appropriate pigment to the dry erase paint formulation.

To increase of toughness and ductility of biopolymers through silane-modified polyester blend is taught by US10875960wherein polyester polymer is homogeneously blended with selective amount of silane molecules containing two or three alkoxy groups bound to the silicon atom.The polyester polymer may, in particular embodiments, be a PLA, polyhydroxyalkanoate, terephthalate-based polyester, adipate-based, or succinate-based polyester.

Preparation method of carboxyl-terminated hyperbranched polyester modified organic silicon resin is disclosed in CN102504293B. The method combines the advantages of the carboxyl-terminated hyperbranched polyester with the organic silicon resin providing excellent heat resistance, excellent metal adhesion, low surface energy, excellent boiling resistance and excellent acid resistance resin. The resin prepared by the method disclosed by the advancement can be used for preparing a coating with high temperature resistance and low surface energy.

US20090017313A1discloses low-gloss anti-graffiti coating formulation comprising a mixture of:an acrylate silica blend for reducing gloss by blending silica and by forming an incompatible phase during curing to produce microroughness;an acrylate selected from a group consisting of an aliphatic urethane acrylate and a polyester acrylate for enhancing physical properties of the mixture;a polyfunctional reactive diluent for increasing crosslink density and a cross-linkable silicone acrylate to enhance the anti-graffiti property of said mixture.

Anti-graffiti imitation ceramic ceiling coating material is provided by CN111057449A which comprises 40-50 wt.% of high performance polyester resin, 10-30 wt.% of silicone modified polyester resin, 0.5-1 wt.% of wetting and dispersing agent, 5-15 wt.% of amino resin, 2-5 wt.% of matting powder, 0.3-0.6 wt.% of leveling agent, 0.3-0.5 wt.% of anti-foaming agent, 0.3-0.5 wt.% of adhesive, 2-20 wt.% of solvent, 0.5-1 wt.% of catalyst, and 0.5-1 wt.% of anti-graffiti additivesand preparation method thereof.

CN110317527A is abouthydrophobic, oleophobic, and anti-graffiti powder coating compositioncomprising 40-60 parts of matrix resin which includes carboxyl polyester resin, hydroxyl polyester resin, epoxy resin, hydroxyl acrylic resin, or epoxy acrylic resin, 3-60 parts of multi-component curing agent comprising at least two curing agents having different curing rates or compatibility with the matrix resin, along with other formulation additives.

Polyurethane-based and epoxy-based anti-smudge and Anti-graffiti coating compositions that provide coatings and adhesives that are clear, amphiphobic and durable is disclosed by US20160200937. Both water and hexadecane readily slide off these surfaces without leaving a residue. The composition comprises:
a major component that is a polymer capable of crosslinking at multiple sites to form a solid material, or a major component that is an engineering plastic preferably polyurethane or epoxy resin; anda minor component that is a polymer having a first end that is capable of binding to the major component and having a second end that remains unbound preferably polydimethylsiloxane, wherein the composition is adapted to be applied to a substrate and dried and/or cured to form a coating on the substrate, such that:the second end of at least a portion of the minor component is located at a surface of the coating; andthe coating is amphiphobic.

US4246380A divulgesa powdery polyurethane lacquer comprising
(A) a hydroxy-group containing polyester resin with an OH number of 40-240 and;
(B) an e-caprolactam-blocked polyisocyanate which is a mixture of the triisocyanatoisocyanurate of 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl -isocyanate with monomeric or oligomeric 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate; and said e-caprolactam-blocked triisocyanatoiso -cyanurate has at least two blocked isocyanate groups, and wherein said e-caprolactam-polyisocyanate is present in an amount sufficient to cause hardening of said mixture of (A) and (B), at temperatures higher than about 150° C.

Graffiti-resistant polyurethane coatingsdisclosed by EP442272A2 is prepared from branched, satd. polyesters (OH no. 180-320 mg KOH/g), polyisocyanates, siloxane-modified polyisocyanates, curing catalysts, and org. solvents. Mixing 2 parts mixt. of a 65% soln. of a highly-branched, satd. polyester (OH no. 265) 65.00, solvents 32.63, a curing catalyst 0.13, flow modifier 0.24, polyester-siloxane 1.00, and UV absorber 1.00 part with 1 part 97:3 mixt. of an aliphatic diisocyanate prepolymer and siloxane-modified polyisocyanate and curing this composition on concrete gave a film from which spray paints could easily be removed by wiping.

While current state of the art discloses powder coating compositions having reasonable technological properties, however they comprise hydroxyl polyester with very high hydroxylnumber/values, or a combination of polyols of different hydroxyl values or use low surface energy liquid such as hydrocarbons and PDMS or follow a complex procedure to provide the anti-graffiti coating formulation.

Thus, there exists a need in the art to explore for improved composition bycompletely eliminating the involvement of high hydroxyl value polyester and process of synthesizing the same which inherently exhibit low melt viscosity and lower Tg, as a result exhibit lump formation during storage.

Objective of the Invention
Thus, the primary objective of the present invention is to provide forpowder polyester and anti-graffiti coating compositionbased thereonsaid polyester which is low-to-middle hydroxyl value based polyesterand completely avoids high hydroxyl counterpart of the same.

Another objective of the present invention is to provide for said powder polyester and anti-graffiti coating composition based thereon preferably based on a single polyester having hydroxyl value ranging from 30-130 mg KOH/gm.

Yet another objective of the present invention is to provide for said powder polyester and anti-graffiti coating composition based thereon whereby the constituent polyester polymer would be free from lump formation during storage and would enable ease of formulation.

Still another objective of the present invention is to provide said powder polyester and anti-graffiti coating composition based thereon that could be formulated for the desired attributes with blocked hardeners, additives including siloxane based surface modifiers and pigments.

Another objective of the present invention is to provide for said powder polyester and anti-graffiti coating compositions based thereon wherein said hardener is preferably based on aliphatic/cycloaliphatic/aromatic blocked hardener and involves small amounts of siloxane basedsurface modifiers.

Yet another objective of the present invention is to provide said powder polyester and anti-graffiti coating compositions based thereonwhich can be used as anti-graffiti coating for appliances such as fan blade, fridge, washing machine, AC compressor unit, white board marker etc.

Still another objective of the present invention is to provide for a process of synthesis of said powder polyester and anti-graffiti coating compositions based thereonby completely eliminating the process of synthesizing and maintaining two SKU’s (Stock keeping unit)of polyester resin, and elimination of extruding process of low surface energy liquid such as hydrocarbons and liquid polysiloxane that is technically challenging and tedious process.

Summary of the Invention

In the primary embodiment the present invention is directed to provide ananti-graffiticoating composition thereof comprising
A) 55-80 wt.% of polyester resin having hydroxyl value in the range of 30-130 mg KOH/gm, weight average molecular weight Mn in the range of 3000 to 5000 and glass transition temperature between 40-68 °C;
B) 15-35 wt.% of aliphatic/cycloaliphatic/aromatic blocked hardener;
C) 0.5 to 4 wt.% of additive including siloxane based surface modifier that is -OH functionalized and polyester modified; and
D) 10-20 wt.% pigments and extenders.

Another embodiment of the present invention is directed to provide saidanti-graffiti coating composition wherein said polyester resin is comprised of reactants including neopentyl glycol (20- 45 wt%), ethylene glycol (0-7 wt%), diethylene glycol (0-5 wt.%), MP diol (1-15 wt%), butyl ethyl propanediol (1-3 wt%), hexane diol (1-3 wt.%) trimethylolpropane (1-15 wt.%), adipic acid (1-3 wt%), terephthalic acid (30-65 wt.%), isophthalic acid (1-20 wt.%), hexahydro phthalic anhydride (1-5 wt.%), pentaerythritol (1-3 wt.%), cyclohexanedicarboxylic acid (1-4 wt.%), cyclohexanedimethanol (1-4 wt.%), having equivalent ratio of polyols to polyacids between 1.10-1.28.

Yet another embodiment of the present invention is directed to provide saidanti-graffiticoating composition wherein said aliphatic/cycloaliphatic/aromatic blocked hardener or mixtures thereof selected from diisocyanates, polyisocyanates and urethdiones, as blocked compounds wherein diisocyanates and polyisocyanates includes hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate,toluylene diisocyanate, cyclohexane diisocyanate,trimethylhexane diisocyanate, tetramethylenexylylene diisocyanate,cyclohexanedimethylene diisocyanate, dicyclohexylmethane diisocyanateor the trimerization products, for example, aliphatic diisocyanate based isocyanurates or mixtures thereof; aromatic diisocyanate including tolylene diisocyanate (TDI), diphenylalkyl diisocyanates or mixtures thereof, wherein the diisocyanates, polyisocyanates and urethdiones are employed as blocked diisocyanates, polyisocyanates and urethdiones blocked with monoalcohols, glycol ethers, ketoximes, lactams, malonic acid esters, acetoacetic acid esters, for example, ethylene glycol monobutyl ether, butanone oxime, phenol, ethyl acetoacetate, dimethylpyrazole or caprolactam.

Further embodiment of the present invention is directed to provide saidAnti-graffiti coating composition wherein said additive include siloxane based surface modifier that is -OH functionalized and polyester modified, degassing agent.

Still further embodiment of the present invention is directed to provide saidanti-graffiti coating composition wherein said siloxane based surface modifier is -OH functionalized and polyester modified, including functional modified polysiloxane, solid supported polysiloxanes including polyester modified-hydroxyl functional polysiloxanes preferably polyester modified-hydroxyl functional polysiloxanes.

Another embodiment of the present invention is directed to provide saidanti-graffiti coating composition wherein said degassing agent includesbenzoin and/or modified wax, pigments selected from transparent, color-imparting and/or special effect-imparting pigments and/or fillers (extenders), inorganic or organic color-imparting pigments includes carbon black, iron oxide, titanium dioxide, micronized titanium dioxide, phthalocyanine, and azopigments, pigments whereas special effect-imparting pigments are metal pigments, made from copper, aluminum, or other metals, interference pigments including metal oxide coated metal pigments and coated mica and usable extenders includes aluminum silicate, barium sulfate, silicon dioxide, magnesium carbonate, calcium carbonate, and micronized dolomite.

Another preferred embodiment of the present invention is directed to provide a method of preparinganti-graffiticoating composition comprising the steps of providing the following ingredients
a. providing 55-80 wt.% of polyester resinhaving hydroxyl value 30-130 mg KOH/gm;
b. providing 15-40 wt.% of aliphatic/cycloaliphatic/aromatic blocked hardener;
c. providing 0.5 to 4 wt.% of additive including siloxane based surface modifiers;
d. providing 10-20 wt.% pigments, extenders and blending and selectively extruding to attain said coating composition thereof.

Further embodiment of the present invention is directed to provide saidmethod of preparing anti-graffiti coating composition wherein the steps of providing polyester resin having hydroxyl value 30-130 mg KOH/gm preferably with select melt viscosity of polyester between 40-70 poise at 200°C is based on synthesis of polyester resin by involving the ingredients of neopentyl glycol (20- 45 wt%), ethylene glycol (0-7 wt%), diethylene glycol (0-5 wt%), MP diol (1-15 wt%), butyl ethyl propanediol (1-3 wt%), hexane diol (1-3 wt%) trimethylolpropane (1-15 wt%), adipic acid (1-3 wt%), terephthalic acid (30-65 wt%), isophthalic acid (1-20 wt%), hexahydro phthalic anhydride (1-5 wt%), pentaerythritol (1-3 wt%), cyclohexanedicarboxylic acid (1-4 wt%), cyclohexanedimethanol (1-4 wt%) maintaining equivalent ratio of polyols to polyacids between 1.10-1.28..

Still further embodiment of the present invention is directed to provide said method of preparing anti-graffiti coating composition wherein the steps includes
i. Mixing saidingredients of the composition and extruding in an extruder at 110-120°C and at RPM of 250-300 to achieve proper dispersion.;
ii. Cooling down the melt-mixed formulation followed by grinding;
iii. Classifying the resulted powder material from step (ii)with 150 mesh size screens to provide for classified powder;
iv. Applying said classified powder by electrostatic spray gun to one side of the aluminum or stainless steel panel;
v. Curing at 180-210 deg C for 25-10 min to provide dry film with a thickness of 70-80 um having anti-graffiti attributes.

Detailed description of the Invention

As discussed hereinbefore, the present invention providesfor powder polyester and anti-graffiti coating compositions thereof preferably in powder form comprising a polyester having hydroxyl value ranging from 30-130 mg KOH/gm together with additives including siloxane based surface modifier and isocyanate hardener including blocked and isocyanate hardener that not only exhibits anti-graffiti feature in powder coating but also in being free from high hydroxyl value/number based polyester inherently advantageously does not exhibit low melt viscosity and lower Tg causing lump formation during storage.
The additives including siloxane based surface modifier of the present invention is characterized by (a) being any OH-functionalized polysiloxane with any number -OH groups, and (b) being necessarily a polyester-modified polysiloxane, and prepared in accordance with US8486188.

As a result,thepresent process completely eliminates the need for as stated high hydroxyl value polyester inherently exhibiting low melt viscosity and lower Tg,causing lump formation during storage and synthesis thereof or maintaining two SKU’s of polyester resin. In addition, the present process is devoid of extruding low surface energy material such as hydrocarbons and liquid polysiloxane which is technically challenging and tedious.During process development it was observed thatextrudingpolysiloxanealong with other ingredients was difficultbecause of slip of as the extruder the material did not come out very easily out of extruder. To overcome this, polysiloxanewas reacted in the backbone of polyester. This material can be easily extruded, but polysiloxane modified polyester appears as hazy and exhibited lower Tg value. Final coating applied using polysiloxanemodified polyester also appears hazy and required anti-graffiti property was not observed.

It is prevalent in the art that for polyurethane paint formulation the hardeners remainsalmost the same irrespective of varying hydroxyl value polyester anyone employs. Major difference of the present invention vis-à-vis the prior arts are involving a single polyester in place of two different hydroxyl functional polyester as taught in prior arts. Siloxane based surface modifier plays an important role in achieving anti-graffiti property. Siloxane based surface modifier in select quantity in combination with select quantity of select hydroxyl value polyester, surprisingly and unexpectedly, show special co-action of the ingredients to provide for desired powder coating.There is certainly synergistic effect of the ingredients when provided together with hardeners including blocked hardener i.e. aliphatic/cycloaliphatic/aromatic blocked hardener, surface modifier,pigments and extenders along with the polyester.

Thus, in accordance with the primary embodiment, the present invention provides for a powder polyester and anti-graffiti coating compositions thereof comprising
A) 55-80 wt% of polyester resin having hydroxyl value in the range of 30-130 mg KOH/gm, weight average molecular weight Mn in the range of 3000 to 5000 and glass transition temperature between 40-68 °C;
B) 15-35 wt.% of aliphatic/cycloaliphatic/aromatic blockedhardener;
C) 0.5 to 4 wt.% additives including siloxane based surface modifier; and
D) 10-20 wt% pigments and extenders.

Said siloxane based surface modifier of the present invention is (a) any OH-functionalized polysiloxane with any number -OH groups, and (b) is necessarily a polyester-modified polysiloxane.

As stated hereinbefore, first major anti-graffiti powder coating composition was provided by US20090018263A1 which comprised of mixture of two polyester resins wherein one is having a hydroxyl number in the range of 30 to 60 mg KOH/g and the other one is having a hydroxyl number in the range of 250 to 350 mg KOH/g. Few other disclosures also followed the similar pathway of using two different polyester polyol for the powder coating formulations. However, the process of synthesizing high hydroxyl value polyester and or storing the same exhibit lump formation due to inherently low melt viscosity and lower Tg, of the polymer. Present invention significantly thusprovides a solution to the above technical problem by providing a single polyester having hydroxyl value ranging from 30-130 mg KOH/gm and formulating it with additives including siloxane based surface modifier that is workable with blocked isocyanate based hardener,to exhibit anti-graffiti feature through powder coating replacingsynthesis and maintenance of two SKU’s of polyester resin.Present process also eliminates the problem of extruding low surface energy material such as hydrocarbons and liquid polysiloxanes.

In another embodiment of the present invention the curing agents used in the formulationare preferably caprolactambased blocked hardener. However, the hardeners suitable for the present invention includes diisocyanates, polyisocyanates and urethdiones, as blocked compounds. Examples of diisocyanates and polyisocyanates are hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate,toluylene diisocyanate, cyclohexane diisocyanate,trimethylhexane diisocyanate, tetramethylenexylylene diisocyanate,cyclohexanedimethylene diisocyanate, dicyclohexylmethane diisocyanate or the trimerization products, for example, aliphatic diisocyanate based isocyanurates or mixtures thereof. Aromatic diisocyanate compounds may also be present, such as, for example, tolylene diisocyanate (TDI), diphenylalkyl diisocyanates or mixtures thereof.
The diisocyanates, polyisocyanates and urethdiones can be used also in blocked form. Blocking may proceed with conventional agents, e.g., with monoalcohols, glycol ethers, ketoximes, lactams, malonic acid esters, acetoacetic acid esters, for example, ethylene glycol monobutyl ether, butanone oxime, phenol, ethyl acetoacetate, dimethylpyrazole or caprolactam.

In another embodiment the present invention also employs coating surface modifiers includingsiloxaneand pigments.Degassing agent such as benzoin and modified wax, surface modifier such as functionallymodified polysiloxane, acrylic based co-polymeror solid supported polysiloxanes or mixture thereof, pigments such astransparent, color-imparting and/or specialeffect-imparting pigments and/or fillers (extenders) are used for the present invention. Inorganic or organic color-imparting pigments includescarbon black, iron oxide, titanium dioxide, micronized titanium dioxide,phthalocyanine, and azo-pigments. Special effect-imparting pigments are metal pigments,made from but not limited tocopper andaluminum, whereas interference pigments, includes metal oxide coated metal pigmentsand coated mica. Examples of usable extenders are aluminum silicate, barium sulfate, silicondioxide, magnesium carbonate, calcium carbonate, and micronized dolomite.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. The advancement according to the present invention is discussed in further detail in relation to the following non-limiting exemplary illustrations wherein:

The basic steps of the process involved in the present invention for preparing a powder polyester and anti-graffiti coating compositions thereofcan be summarized as follows:
1.a. Preparation of polyester polyol with hydroxyl value 30-130 mg KOH/gm, with weight average molecular weight Mn in the range of 3000 to 5000 and glass transition temperature between 40-68 °C, and providing 55-80 wt% of thus prepared polyester resin;
b.Providing 15-35 wt% of aliphatic/cycloaliphatic/aromatic blocked hardener;
c.Providing additive 0.5 to 4 wt.% including siloxane based surface modifier and
d.Providing 10-20 wt% pigments and extenders to thereby formulate said anti-graffiti coating;
2. Extrusion and grinding;
3. Applyingsaid powder obtained from step (2) above with electrostatic spray gunfollowed by curing based on the hardeners present in said formulation at temperatures of 180-210 deg C for 25-10 min to provide for a dry film.

Example-1

Synthetic protocol forpolyester (a): A 2000 mL, 3-necked, round bottom flask equipped with a stirrer, a short pack column, dean stark, condenser and an inlet for nitrogen, was charged with ethylene glycol (31.84 gm), diethylene glycol (47.84 gm), MP diol (207.68 gm), neopentyl glycol (319.52 gm), tin based catalyst, and triphenyl phopshite, material was heated to 120-140 °C followed by addition of terephthalic acid (990 gm). After complete addition, the reaction was heated to 190°Cover 30 minutes. The reaction was then maintained, under nitrogen, at 190° C. for 1-2 hours with stirring. Reaction temperature was taken to 240 °C gradually over 10-12 hrs. After cold and hot clarity of material is obtained (Cold and hot clarity mean, material is removed on a glass plate from the reactor to see the clarity of material in hot as well atroom temperature conditions), vacuum applied to reduce acid value below 5 mgKOH/gmand desired melt viscosity. After attaining the desired constants molten mass is discharged in stainless steel tray.Hydroxyl value is controlled by varying equivalent ratio of polyols to polyacids between 1.10-1.28.

Synthetic protocol for polyester (b): A 2000 mL, 3-necked, round bottom flask equipped with a stirrer, a short pack column, dean stark, condenser and an inlet for nitrogen, was charged with ethylene glycol (64 gm), neopentyl glycol (560 gm), tin based catalyst, and triphenyl phopshite, material was heated to 120-140 °C followed by addition of isophthalic acid (128 gm), terephthalic acid (845.4 gm). After complete addition, the reaction was heated to 190°Cover 30 minutes. The reaction was then maintained, under nitrogen, at 190° C. for 1-2 hours with stirring. Reaction temperature was taken to 240 °C gradually over 10-12 hrs. After cold and hot clarity of material is obtained, vacuum applied to reduce acid value below 5 mgKOH/gm and desired melt viscosity. After attaining the desired constants molten mass is discharged in stainless steel tray.

Raw Materials Formula 1 Formula 2
Ethylene glycol 1.99 4
Diethylene glycol 2.99 -
MP Diol 12.98 -
Neopentyl glycol 19.97 35
Terephthalic acid 61.91 52.84
Isophthalic acid - 8
Tg (°C) 55 65
OHValue mgKOH/gm (Theoretical) 30 50
Melt viscosity (Poise) @ 200 °C 62 57
GPC Mn-4370 Mw-9800
PDI-1.55 Mn-3730 Mw-7780 PDI-2.08

Polyester polyols with varying composition, hydroxyl value, and molecular weight give, required glass transition temperature, branching, flexibility, cross linking density, better dispersion during extrusion and flow during curing.

Method for paint formulations

Melt viscosity plays a vital role for extrusion and the higher is the melt viscosity better is the extrusion. Temperature range, RPM are critical to have a better melting of raw material and resulting in good dispersion and thus leads to better finish of coating. For the present invention Melt viscosity between 40-70 poise at 200°C was found to be most appropriate.
For extrusion ingredients of the composition are mixed and extruded in an extruder at 110-120°C and at RPM of 250-300 to achieve proper dispersion. The melt-mixed formulation is then cooled, broken down, and the resulted material is classified by 150 mesh size screens.The powder is applied by electrostatic spray gun to one side of the aluminum or stainless steel panel. Applied coating is cured at oven at 180-210 deg C for 25-10 min to provide dry film.

Example-2
Polyester, hardener, degassing agent, surface modifier, pigments, extenders of each composition were melt-mixed separately in twin screwextruder at 110 to 120 °C and at RPM of 250-300 to achieve proper dispersion. The melt-mixed formulation is then cooled. Resulting chips materials were grounded and classified by 150 mesh size screens. The powder was applied by electrostatic spray gun to one side of the 6 * 4 inch, 1.2 mm aluminum or stainless steel panel. Applied coating was cured at oven for20 minutes at 200° C to provide dry film thickness of 70-80 um.In the experimentation there was no hurdle in extrusion and or storage stability.
Raw Materials Formula 1 Formula 2
Polyester a 69.589 --
Polyester b -- 63.470
Blockedhardener 15.379 20.569
Degassing agent 0.808 0.920
Additive including siloxane based surface modifier, 2.542 2.542
Pigments and extender 11.682 12.499

Thus, the present invention enables successful preparation of the powder coating with very good anti-graffiti property wherein Graffiti resistance was checked by ASTM D6578 using dry cotton cloth method.Importantly, there was no storage stability problem of ingredients of the coating andno hurdle in extrusion was encountered during preparation of the coating formulation.