[0001] Disclosed herein is a coating composition able to provide a matt finish, for example, for use in coating leather, wood, metal and/or plastics surfaces. Also provided is a method of making the coating composition.

[0002] Treating surfaces by the application of a coating (i.e. a substance capable of covering the surface of a substrate) is commonly practiced in order to protect surfaces from abrasion, corrosion and/or oxidization. Coatings may also be applied to surfaces in order to provide the surfaces with a pleasant visual or tactile effect. Such coatings may be applied to the surface of many substrates, for example leather, wood, metal and/or plastics. Coatings are conventionally composed primarily of binders, such as

polyurethanes, acrylics, epoxys, ethylene vinyl acetates and styrenes.

[0003] Often, however, surfaces coated with simple binders alone do not offer an optimum surface coating. For example, coatings consisting of polyurethane alone provide too shiny a surface.

[0004] As a consequence of this, Dow Corning ^® 23 N Additive has been used in combination with binders, such as polyurethane water based dispersions, to form a coating and has been shown to greatly improve the function of such coatings. Dow Corning ^® 23 N Additive is a white powder additive with relatively small particles; the particles are of an average particle size of 2μηι and with have particle size distribution of between 1 to Ι Ομηι. These particles are formed from a cross-linked silicone elastomer, more specifically a cross-linked epoxy functional silicone formed in a condensation reaction of silanol and methoxy silane in the presence of a tin catalyst. The silicone is formed by reacting its monomers in a liquid that is immiscible with the silicone and in the presence of a surfactant. The resulting emulsion is then spray dried so as to form a silicone elastomeric powder. In order to provide the required matt effect in normal coatings, which are usually applied at thicknesses exceeding Ι Ομηι, the silicone elastomeric powders are then agglomerated so as to form agglomerates of Ι Ομηη or more. The resulting silicone elastomeric powder (i.e. Dow Corning ^® 23 N Additive) is mixed with a binder before application of the mixture to the chosen surface. Dow

Corning ^® 23 N Additive when used as an additive in solvent and aqueous coatings imparts to those coatings an excellent level of mar and abrasion resistance and a smooth matt finish.

[0005] Dow Corning® 23 N Additive has become a well established product for use in premium coatings. However, the cost of manufacture of this additive means that coating that include the additive are relatively expensive. This is particularly problematic for coating surfaces that require a reasonable degree of matt finish but that need to be manufactured in high volume at low cost. [0006] In seeking to identify a more cost efficient additive for providing matt finish to a coating composition, rather than the obvious first step of looking to modify Dow Corning® 23 N Additive, the present inventors looked to other known silicone elastomeric powders (such as those used for providing cosmetics with a soft matt finish). Unfortunately, it was identified that such known elastomeric powders did not provide coatings to which they were added a satisfactory level of matt finish and ease of use (i.e. dispersibility in a water based binder).

BRIEF SUMMARY OF THE INVENTION

[0007] Disclosed herein are coating compositions and methods of making the coating compositions.

[0008] A surface once coated with the coating compositions of the present invention is provided with a matt finish.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Accordingly, in the first aspect of the present invention there is provided a coating composition comprising a binder, an elastomeric silicone powder formed by spray curing and a stabilizing agent.

[0010] In the second aspect of the present invention there is provided a coating composition comprising a binder, an elastomeric silicone powder and a stabilizing agent, wherein the elastomeric silicone powder is made or obtainable by forming a mixture of organopolysiloxane A and organopolysiloxane B, wherein organopolysiloxane A comprises more than 0.5 % alkenyl groups by weight of the organopolysiloxane A, organopolysiloxane B comprises from 0.25% to 1 % silicon-bonded hydrogen atoms by weight of the organopolysiloxane B, wherein the stabilizing agent comprise a

functionalized silane, silazane, a silicone glycol copolymer, or any combination thereof, with the elastomeric silicone powder optionally formed by spray curing.

[0011] An elastomeric silicone powder sometimes called e-powder or silicone powder is a silicone polymer in solid form, especially in finely divided particles. The silicone powder is usually elastomeric which means it has some elasticity. Such elastomeric silicone powder can be prepared for example by spray curing or by spray drying. A spray curing process typically involves the spraying of the reactants in a substantially liquid form into a curing chamber. Usually heat is applied to effect curing. There is usually no surfactant in the reactive mixture. The reactants are not emulsified. By contrast, in a spray drying process, the reactants mixed with surfactant are emulsified then cured and the cured composition is spray dried to take out the solvent, which is typically water. A spray drying process involves more steps than spray curing.

[0012] A siloxane is a compound which contains at least one Si-O-Si link. A polymer is a compound containing repeating units. A siloxane polymer also called polysiloxane or silicone is a polymer containing repeating Si-O-Si units. An organosiloxane compound is a siloxane containing at least one organic group. A silane contains silicon and is usually monomeric. A silane as meant herein is typically an organosilane i.e. a compound that contains at least one Si-C link. A functionalised silane as used herein is a silane containing at least one Si-C link and at least one functional group such as, for example, a group containing at least one of the following functionalities: amino, (meth)acrylate, epoxy, vinyl, mercapto, glycidoxy, sulfido, isocyanate, alkoxy.

[0013] The inventors have surprisingly found that by using a spray cured elastomeric powder in association with a stabilizing agent, one can produce a coating composition according to the present invention that provides a satisfactory level of matt finish, whilst being cheaper to manufacture than Dow Corning® 23 N Additive. The manufacturing process of the present invention is particularly advantageous as the particles of the powder may be made at a size that eliminates the need for a step of agglomeration.

Binder

[0014] A binder of the present invention may be any substance used as a coating itself, or a substance used as a binder in a coating composition. The binder holds all components of the composition together when the coating coats the substrate. For example, the binder may comprise or consist of a polyurethane polymer, an acrylic polymer, a vinyl ether polymer, a poly(styrene-butadiene polymer), an alkyd resin, alkyd emulsion polymer, a phenolic resin, a polyvinyl acetate polymer, a nitrocellulose polymer, or any combination thereof. The binder may be provided as a dispersion in a solvent or water, for example a polyurethane dispersion in water and/or an acrylic polymer dispersion in a solvent. The binder may comprise from 30% to 99.5% of total weight of coating composition.

Elastomeric Silicone Powder

[0015] Elastomeric silicone powders are made of particles with the ability to be

deformable, but to resume their original shape after the deforming force is removed. The elastomeric silicone powders of the present invention are required to be formed by spray curing, a process that is well understood by the person skilled in the art. For example, spray cured silicone powders may be created by reacting organopolysiloxane reactants that are provided in a liquid form and are forced into an atomized state in a spray curing tank where the curing takes place without the need to evaporate a solvent, e.g. water. The atomized state is reached by spraying or vaporising the liquid mixture in the curing tank at a temperature ranging of from +20 to +350°C, alternatively of from +80 °C to +350 °C, alternatively of from +80 °C to +250 °C. Importantly, this process of spray curing is not the same as spray drying. Spray drying is a process where a solvent such as water is removed by atomization of a dispersion or emulsion of the already formed silicone. The spray drying process does not involve a reaction that forms the silicone of the elastomeric silicone powders.

[0016] Therefore, the elastomeric silicone powders of the present invention may be produced without the use of a surfactant.

[0017] The spray curing process produces particles of a large size, relative to those produced by spray drying in the formation of Dow Corning® 23 N Additive. The average particle size (i.e. average of the largest diameter passing through the center point of each particle in the powder) for particles of the elastomeric silicone powders of the present invention may be from 1 to 100 μηη, 5 to 50 μηη, 10 to 40μηι, 10 to 30 μηη, 10 to 25μηι, 10 to 20μηι or 10 to 15 μηι. The average particle size should be preferably above 10 μηη.

[0018] The elastomeric silicone powders of the present invention may be made by forming a mixture of organopolysiloxane A and organopolysiloxane B, wherein organopolysiloxane A comprises alkenyl groups and organopolysiloxane B comprises silicon-bonded hydrogen atoms, and the mixture is spray cured to form the elastomeric silicon powders. More particularly, the elastomeric silicone powder may be made by (i) forming a mixture of organopolysiloxane A and organopolysiloxane B, wherein organopolysiloxane A comprises more than 0.5 % alkenyl groups by weight of the organopolysiloxane A, organopolysiloxane B comprises from 0.25% to 1 % silicon- bonded hydrogen atoms by weight of the organopolysiloxane B, and; (ii) spray curing the mixture of step (i) to form an elastomeric silicone powder.

[0019] Organopolysiloxanes may generally comprise various siloxy units such as (i) (R ₃ Si0 ₁ / ₂ )a' , (ϋ) (R2Si0 ₂ / ₂ )b' , (iii) (RSi0 _3/2 ) _c ^< , or (iv) (Si0 _4/2 ) _d ^< units which are commonly known in the art, and also used herein, as M, D, T, and Q units respectively, wherein R is a monovalent organic group; a', b', c' and d' have a value of from 0 to 0.9, with the proviso that the value of a' + b' + c' + d' = 1 . When 2 or more R are present on one Si atom, they can be the same or different. The R groups can be different on different Si atoms or they can be the same.

[0020] Monovalent organic groups include hydrocarbons such as alkyl groups (e.g.

methyl, ethyl, propyl, isopropyl, butyl, octyl, nonyl, tetradecyl and/or octadecyl); cycloalkyl groups (e.g. cyclohexyl and/or cycloheptyl); alkenyl groups (e.g. vinyl and/or hexenyl); aryl groups (e.g. phenyl, diphenyl and/or naphthyl); alkaryl groups (e.g. tolyl, xylyl and/or ethylphenyl); aralkyl groups (e.g. benzyl and/or phenylethyl); or any mixture thereof. In some preferred embodiments, R is methyl or phenyl.

[0021] The monovalent organic group may contain substituents other than carbon and hydrogen atoms, such as halogen atoms (chlorine, fluorine, bromine, iodine); halogen atom containing groups such as haloalkyl groups (chloromethyl, perfluorobutyl, trifluoroethyl, and nonafluorohexyl) and haloaryl groups (monochlorophenyl, dibromophenyl, tetrachlorophenyl, monofluorophenyl); oxygen atoms; oxygen atom containing groups such as hydroxy, carboxyl, carbinol, ester, ether, acrylic groups and polyoxyalkylene groups (polyoxyethylene, polyoxypropylene, polyoxybutylene); nitrogen atoms; nitrogen atom containing groups such as nitrile, amino, amido, cyano, cyanoalkyl and urethane groups; sulphur atoms; sulphur atom containing groups such as sulphide, sulphone, sulphate, sulphonate and mercapto groups; phosphorus atoms; phosphorus atom containing groups such as phosphate, phosphate and phosphonate groups; or any mixture thereof.

[0022] The letter designations M, D, T, and Q, refer respectively, to the fact that the siloxy unit is monofunctional, difunctional, trifunctional, or tetrafunctional. These M, D, T, and Q structural units are de icted below for the sake of clarity

(T) (Q)

[0023] Organopolysiloxanes A and/or B may be cyclic, linear, branched, or crosslinked. A cyclic organopolysiloxane would be considered to be one that includes predominantly or only D-units and optionally T units, but typically no M unit in the ring. A linear

organopolysiloxane would be considered to be one that includes predominantly D units and which is terminated by M units. A branched organopolysiloxane would be considered to include at least 1 T or at least 1 Q unit, along the chain or at terminal positions.

Organopolysiloxane resins are examples of branched organopolysiloxanes, where more than 30% of siloxy units, alternatively more than 80 % siloxy units, are either T or Q units.

[0024] The Organopolysiloxane A may have the alkenyl groups in terminal and/or pendant positions or both. Organopolysiloxane A has at least 2 alkenyl groups. The alkenyl group may be linear or cyclic, composed of from 2 to 10 carbon atoms, alternatively of from 2 to 6 carbon atoms, such as hexenyl, vinyl, allyl or pentenyl or cyclohexenyl. Organopolysiloxane A may be any combination of two or more of organopolysiloxanes each comprising at least 2 alkenyl groups.

[0025] Organopolysiloxane A may be an MQ resin consisting of units of the general formula Si0 _4/2 and R ^q ₃ Si0 _1/2 wherein at least 2 R ^q substituents are alkenyl groups and the remainder are alkyl groups. [0026] Suitable organopolysiloxanes A may be of the Q-branched structure, that is optionally including at least 1 Q unit. Preferably the Q-branched organopolysiloxane A includes at least 1 Q unit and further D and M units, optionally T units, such as (MD) ₄ Q organopolysiloxanes. Organopolysiloxanes A may conform to Formula I, comprising more than 0.5 % alkenyl groups by weight of the organopolysiloxane A:

Formula I

wherein each R ^a substituent is independently defined and is an alkyl group having 1 -6 carbon atoms, an alkenyl group having 2-6 carbon atoms, or an alkynyl group having 2-6 carbon atoms; each R ^b substituent is independently defined and is an alkyl group having 1 -6 carbon atoms, an alkenyl group having 2-6 carbon atoms, an aryl group, an alkoxy group, an acrylate group, or a methacrylate group; n is 1 -200; and provided that at least 3.2-3.9 of the R ^a substituents are alkenyl or alkynyl groups. Further details of Q-branched organopolysiloxanes according to Formula I and that comprise more than 0.5 % alkenyl groups by weight are described in International Patent Publication No. WO/2006/055233, each of which may be an organopolysiloxane A of the present invention. The

organopolysiloxane A may be selected from those Q-branched organopolysiloxanes discussed above and that have a viscosity of < 400 mm ² /s. Consequently, the disclosures of such organopolysiloxanes described in International Patent Publication No.

WO/2006/055233 is incorporated herein by reference.

[0027] Organopolysiloxane A may conform to the general formula

R ^c R ^d ₂ SiO(R ^d ₂ SiO) _x .(R ^d R ^e SiO) _y .SiR ^d ₂ R ^c

where each R ^d denotes an alkyl or cycloalkyi group having from 1 to 10 carbon atoms, for example, methyl, ethyl, propyl, butyl or cyclohexyl; each R ^c and R ^e denotes an alkenyl group or an alkynyl group; and x' and y' are such that Organopolysiloxane A has a viscosity at 25°C of < 400 mm ² /s.

[0028] Organopolysiloxane A may comprise from 0.5 to 15% , 0.5 to 10%, 0.5 to 5% alkenyl groups by weight of organopolysiloxane A. Organopolysiloxane A may comprise 0.8% alkenyl groups by weight of organopolysiloxane A.

[0029] The Organopolysiloxane B comprising silicon-bonded hydrogen atoms may be a cyclic, linear, or branched organopolysiloxane, or any mixture thereof.

Organopolysiloxane B may be any combination of two or more of organopolysiloxanes comprising a silicone-bonded hydrogen atom.

[0030] Organosiloxane B may be selected from those according to Formula II, comprising of from 0.25% to 1 % silicon-bonded hydrogen atoms by weight of the organopolysiloxane B,

[R ^f ₂ HSiOi _/2 ] _k . [R ^f ₃ SiOi _/2 ], [R ^f HSi0 _2/2 ] _m ^< [R ^f ₂ Si0 _2/2 ] _s . [R ^f Si0 ₃ / ₂ ] _P ^< [Si0 _4/2 ] _q ^< Formula II where R ^f may designate a univalent organic group (e.g. methyl or phenyl) that does not contain aliphatic unsaturation; k'≥ 0; r'≥ 0; 1 < k' + r' < 10; 30 < m' < 200; 10 < s' < 100; 0 < p' < 10; q' = 1 ; and (k' + r' + m' + s' + p' + q') is such that the viscosity of

organopolysiloxane B is < 100 mm ² /s.

[0031] Further details of organopolysiloxanes B according to Formula II and that comprise of from 0.25% to 1 % silicon-bonded hydrogen atoms by weight are described in Japanese Patent Application No. 200721 1 186 A, each of which may be

organopolysiloxane B of the present invention, such that the viscosity of

Organopolysiloxane B < 100 mm ² /s. Consequently, the disclosures of such

organopolysiloxanes described in Japanese patent Application No. 200721 1 186 are incorporated herein by reference.

[0032] Organopolysiloxane B may have the general formula:

R ⁹ ₃ Si0 _1/2 ((CH ₃ ) ₂ Si0 _2/2 ) e'(R ⁹ ₂ Si0 _2/2 ) _f )Si0 _1/2 R ⁹ 3

where each R ⁹ may be independently selected from an alkyl group having 1 to 4 carbon atoms or hydrogen, e' is 0 or an integer, f is an integer such that e' + f is such that the viscosity of Organopolysiloxane B < 100 mm ² /s.

[0033] Organopolysiloxane B may be selected from organohydrogenpolysiloxanes comprising at least one cyclosiloxane, according to Formula III, comprising from 0.25% to 1 % silicon-bonded hydrogen atoms by weight of the organopolysiloxane B

Formula III. (0-SiRX) _a (OSiR ₂ ) _b

where each R is independently selected from a hydrogen atom and a monovalent hydrocarbon group comprising 1 to 20 carbon atoms which is free from aliphatic unsaturation, a is an integer from 1 to 18, b is an integer from 1 to 19, a + b is an integer from 3 to 20, each X is an independently selected functional group selected from a halogen atom, an ether group, an alkoxy group, an alkoxyether group, an acyl group, an epoxy group, an amino group, or a silyl group, or a -Z-R ^h group, where each Z is independently selected from an oxygen and a divalent hydrocarbon group comprising 2 to 20 carbon atoms, each R ^h group is independently selected from - SiR _v Y ₃ . _v , or a group described by formula (IV):

Formula IV: (Y ₃ - _u R _u Si0 _1/2 ) _c (Y ₂ _ ₀ R ₀ Si0 _2/2 ) _d (Y _l _ _p R _p Si0 _3/2 )e(Si0 _4/2 ) _f (CR _q Y ₁ _ _q ) _g (CR _r Y ₂ _ _r ) _h (0(CR _s Y ₂ _ _s ) _i (CR _t Y ₃ -,) _j

where each R is as described above, the sum of c+d+e+f+g+h+i+j is at least 2, u is an integer from 0 to 3, o is an integer from 0 to 2, p is an integer from 0 to 1 , q is an integer from 0 to 1 , r is an integer from 0 to 2, s is an integer from 0 to 2, t is an integer from 0 to 3, v is an integer from 0 to 3, each Y is an independently selected functional group selected from a halogen atom, an ether group, an alkoxy group, an alkoxyether group, an acyl group, an epoxy group, an amino group, a silyl group, or a Z-G group, where Z is as described above, each G is a cyclosiloxane described by formula (V):

I 1

Formula V : (OSiR)(OSiRX) _k (OSiR ₂ ) _m

where R and X are as described above, k is an integer from 0 to 18, m is an integer from 0 to 18, k+m is an integer from 2 to 20, provided in formula (IV) that one of the Y groups is replaced by the Z group bonding the R ^h group to the cyclosiloxane of formula (III), and provided further (a) at least one X group of Formula (III) is a - Z-R ^h group; (b) if Z is a divalent hydrocarbon group, a=l, c = 2, e+f+g+h+i +j = 0 and d>0, then at least one d unit (i.e. Y ₂ - ₀ R ₀ Si0 _2/2 ) contain a -Z-G group or the c units (i.e. Y ₃ . _u R _u Si0 _1/2 ) have no -Z-G group or at least two -Z-G groups, (c) if Z is a divalent hydrocarbon group, a=l, c = 2 and d+e+f+g+h+i +j = 0, then the c units (ie. Y ₃ . _u R _u SiOi _/2 ) have no -Z-G group or at least two - Z-G groups, and (d) if g+h+i+j >0 then c+d+e+f>0.

[0034] For example, organopolysiloxane B according to Formula III may be the compound of Formula V, where Me is methyl, d is an average of 8 and x is an integer from 1 to 15.

Formula V

[0035] Further details of organopolysiloxanes according to Formula III and that comprise of from 0.25% to 1 % silicon-bonded hydrogen atoms by weight are described in

International Patent Publication No. WO2003/093349, each of which may be

organopolysiloxane B of the present invention, such that the viscosity of

Organopolysiloxane B < 100 mm ² /s. Consequently, the disclosure of such

organopolysiloxanes described in International Patent Publication No. WO2003/093349 is incorporated herein by reference.

[0036] In order to enhance the mixing or organopolysiloxane A and B, the

organopolysiloxanes may be liquid at standard ambient temperature and standard atmospheric pressure. Organopolysiloxane A may have a viscosity < 400 mm ² /s.

Organopolysiloxane B may have a viscosity < 100 mm ² /s. Selecting organopolysiloxanes with the appropriate viscosity enables the mixing to occur without the need for solvents for the organopolysiloxanes. Consequently, the step of mixing organopolysiloxane A and/or B with a solvent may be absent from the method of the present invention.

[0037] The molar ratio of the alkenyl groups of organopolysiloxane A to the silicon- bonded hydrogen atoms of organopolysiloxane B in the mixture may typically be of from 0.5:1 .5 to 1 .5:0.5, alternatively 1 :1 . A slight excess of either one of organopolysiloxane A or organopolysiloxane B, that is, within the molar ratio of from 0.5:1 .5 to 1 .5:0.5, provides for a reaction producing a satisfactory elastomeric silicone powder.

[0038] The silicone elastomeric polymer may be made from a mixture of

organopolysiloxane A and organopolysiloxane B, wherein organopolysiloxane A is Q branched has a viscosity of about 100 mm ² /s and comprises about 1 .17 % alkenyl groups by weight of the organopolysiloxane A, organopolysiloxane B has a viscosity of about 70 mm ² /s and comprises about 0.92 % silicon-bonded hydrogen atoms by weight of the organopolysiloxane .

[0039] The coating composition may include 5-20, 5-10, 5-15, 8-12, 9-1 1 10-20, 15-20% by weight elastomeric silicone powder.

Stabilising Agent

[0040] A stabilizing agent may be any agent that is able to improve the retention and/or distribution of the elastomeric silicone polymers of the present invention in the binder. The stabilizing agent may, for example, comprise or consist of a functionalized silane, a silazane, a wetting agent, or combinations thereof. The stabilizing agent may be silica, preferably hydrophilic silica for example Aerosil ® fumed silica.

[0041 ] Functionalised silanes may comprise or consist of amino functionalized silanes (such as aminoethylaminopropyltrimethoxysilane, aminopropyltriethoxysilane and aminopropyltrimethoxysilane), methacrylate or acrylate functionalised silanes (such as methacryloxypropyltrimethoxysilane), epoxy functionalised silanes (such as

glycidoxypropyltrimethoxysilane), vinyl functionalised silanes (such as

vinyltrimethoxysilane), ethoxy functionalised silanes (such as tetraethoxysilane and tetraethylorthosilicate ).

[0042] Preferably, the function of the functionalised silane is chosen for its compatibility with the binder. For example an epoxysilane is preferred for polyurethane (PU) binder, as epoxy is compatible with PU or an acrylic silane is chosen for an acrylic binder.

The silazane may be hexamethyldisilazane.

[0043] The wetting agent may be any agent that has a Hydrophilic-lipophilic balance (HLB) that is higher than 6, optionally between 1 1 and 30. The HLB value may be calculated by the Griffin method ( see, incorporated herein by reference, Griffin, William C. (1954), "Calculation of HLB Values of Non-Ionic Surfactants", Journal of the Society of Cosmetic Chemists 5 (4): 249-56). The Griffin method calculate HLB as follows:- HLB = 20 * Mh/M

where Mh is the molecular mass of the hydrophilic portion of the molecule, and M is the molecular mass of the whole molecule, giving a result on a scale of 0 to 20. An HLB value of 0 corresponds to a completely lipophilic/hydrophobic molecule, and a value of 20 corresponds to a completely hydrophilic/lipophobic molecule.

[0044] Not wishing to be restricted further, as an example, suitable wetting agents may be a silicone polyether such as silicone glycol copolymer (e.g. a trisiloxane ethoxylate

[0045] It has been found that combinations of the stabilising agent are particularly effective. For example, the use of a combination of a silicone polyether (such as trisiloxane ethoxylate) and an epoxy silane (such as glycidoxypropyltrimethoxysilane).

[0046] The inventors have found that applying the stabilizing agent to the surface of the elastomeric silicone powders prior to the mixing of the binder and the elastomeric silicone powder improves the finish of the coating.

[0047] Preferably, the stabilizing agent is added to an already formed elastomeric silicone powder. This is the post-addition embodiment. This permits to form first the elastomeric silicone powder as usual, without need to change the process to allow for the presence of an additional component during spray cure. This post addition provides hydrophilicity to the elastomeric silicone powder which is otherwise hydrophobic. Weight ratio of stabilizing agent would be between 0.5% and 5.0%. Presence of stabilizing agent above 5.0% would make the silicone powder highly viscose (sticky), causing problem in flowability and dispersibility. Also, silane/silicone glycol content transfer might occur in the coating formulation, which causes defects in the final coating.

[0048] Consequently, in a second aspect of the present invention, there is provided a method of preparing the coating composition of the first aspect of the present invention, comprising the steps of coating one or more spray cured elastomeric silicone powder of the first aspect of the present invention with one or more stabilizing agent of the first aspect of the present invention prior to mixing the elastomeric silicone powder with the binder.

[0049] When making the spray cured elastomeric powder, organopolysiloxane A and organopolysiloxane B may be mixed in step (i) prior to step (ii). This may be achieved by mixing in a batch reactor, or continuously, for example in a static mixer or in a dynamic mixer, or directly in a nozzle, such as in a mixing nozzle. Batch reactor mixing and continuous mixing are known mixing techniques in the art. After mixing, the mixture is then fed to the spray curing tank via a nozzle (e.g. rotary nozzle) where step (ii) takes place. When the mixing takes place in a mixing nozzle, the two organopolysiloxanes are fed to the nozzle separately, but are mixed in the nozzle before the mixture is sprayed into the spray curing chamber during step (ii).

[0050] Alternatively, the mixing of organopolysiloxane A and organopolysiloxane B in step (i) occurs simultaneously with the spray curing of step (ii). For example, a 2-fluid nozzle may transmit the organopolysiloxanes to the spray curing chamber simultaneously but in separate conduits (i.e. co-spraying), thereby only permitting mixing of the

organopolysiloxanes during step (ii). Other appropriate nozzles may be used such as rotary nozzle, pressure nozzle, trifluid nozzle, and further nozzles known in the art. Spray curing devices are known in the art, and may also be known as spray dryer devices. These devices may possess various settings, such as inlet and outlet temperatures, pressure, vacuum appliances, heat appliances, sieves, scrapers.

[0051 ] Step (i) may be carried out at a temperature of above 5°C, optionally from 5 to 100°C, alternatively from 15 to 90°C, alternatively from 15 to 70°C.

[0052] In order to reduce the potential for organopolysiloxane A and B reacting prior to their release into the spray curing chamber, when step (i) and (ii) are not simultaneous, step (i) may include the addition of an inhibitor. The inhibitor may be added to

organopolysiloxane A prior to mixing this pre-mixture with organopolysiloxane B.

Alternatively, the inhibitor may be added to organopolysiloxane B prior to mixing this pre- mixture with organopolysiloxane A. Alternatively, organopolysiloxane A,

organopolysiloxane B and the inhibitor may be simultaneously mixed together. [0053] The inhibitor may be selected from addition-reaction inhibitors. Addition-reaction inhibitors may be any one or more of : hydrazines, triazoles, phosphines, mercaptans, organic nitrogen compounds, acetylenic alcohols, silylated acetylenic alcohols, maleates, fumarates, ethylenically or aromatically unsaturated amides, ethylenically unsaturated isocyanates, olefinic siloxanes, unsaturated hydrocarbon monoesters and diesters, conjugated ene-ynes, hydroperoxides, nitriles, diaziridines and mixtures thereof. The inhibitor may be added in the range of from 10 to 50,000 weight-ppm (parts per million) in the mixture of organopolysiloxane A and B.

[0054] The method of the present invention may include the step of adding a catalyst during step (i). The catalyst may be added to organopolysiloxane A or B, or to the mixture thereof. The catalyst may be added after the addition of the inhibitor. The catalyst may be added to organopolysiloxane A, and the inhibitor to organopolysiloxane B, or inversely.

[0055] The catalyst may be selected from the platinum group metals, or transition metals, of the periodic table of the elements, such as platinum, ruthenium, rhodium, palladium, osmium and iridium, and compounds thereof, and mixtures thereof. Specific examples of these catalysts include those based on platinum such as chloroplatinic acid, chloroplatinic acid dissolved in an alcohol or a ketone and these solutions which have been ripened, chloroplatinic acid-olefin complexes, chloroplatinic acid-alkenylsiloxane complexes, chloroplatinic acid-diketone complexes, platinum black, and platinum supported on a carrier. The catalyst is to be added in a quantity sufficient to enable curing of the mixture during step (ii). For example, the catalyst may be added in a quantity that provides of from 0.1 to 1 ,000 weight-ppm, alternatively of from 1 to 500 weight-ppm, alternatively of from 40 to 250 weight-ppm, of platinum metal in the catalyst based on the total weight of organopolysiloxane A and B.

[0056] The step of curing the mixture in step (ii) may be achieved by a condensation reaction, e.g. a hydrosilylation reaction. The temperature at which the step of curing occurs (i.e. the temperature at the exit of the nozzle into the spray curing chamber in which step (ii) occurs) is of from 80 to 300°C, alternatively of from 100 to 250°C, alternatively of from 100 to 200°C.

[0057] The method may further include step (iii), wherein the elastomeric silicone powder produced during step (ii) is collected from the spray curing chamber in which step (ii) is carried out. Step (iii) may be carried out in a cyclone. Filters may also be used in step (iii) in order to collect powders of the desired size and/or weight.

[0058] The method may be solventless or may further include step (iv), wherein the elastomeric silicone powder may be dispersed in a solvent or a mixture of solvents.

Examples of solvents include organic solvents (such as aliphatic compounds (hexane, mineral oil, isododecane, (iso-)paraffins); aromatic compounds (toluene, xylene, benzene); mineral spirits; methyl ethyl ketone; n-butyl acetate; t-butyl alcohol; ethylene glycol; vegetable oils (castor oil, sunflower oil, olive oil, coconut oil, rice bran oil); alcohols (ethanol, isopropanol)); silicone oils (such as cyclosiloxanes, dimethicones of viscosities of from 0.5 to 10,000 mm ² /s, caprylyl methicone); water. Preferably, no solvent is used.

[0059] All features of the first aspect of the present invention may apply to those of the second aspect of the present invention. All features of the second aspect of the present invention may be applied to those of the first aspect of the present invention.

[0060] As described above, the elastomeric silicone powder of the present invention may be characterized by the size of particle or agglomerate produced by the method. The skilled person would be well aware how to analyse the size of particles or agglomerates. However, for the avoidance of doubt, the size may be analysed by visual analysis using a microscope. More particularly, several (e.g. 5 or more) random images of the collected elastomeric silicone powder may be viewed at the same magnification via a microscope and the diameter of the particles or agglomerates in each view determined. A mean of all determined diameters is then calculated and may be used to characterize the size of the elastomeric silicone powder.

[0061] The particles of the powder of the present invention may be substantially spherical. Particle that are substantially spherical are those in which all diameters across the central point of the particle deviate by no more than 20%, alternatively not more than 10%, alternatively not more than 5%.

[0062] Various methods exist which may be used to quantify the levels of silicon bonded hydrogen atoms or alkenyl groups.

[0063] Such methods or techniques include, but are not limited to, titration, infra-red, near infrared (FT-NIR), volumetry of hydrogen gas, and nuclear magnetic resonance (NMR). 29Si NMR spectroscopy may be used to determine the content of silicon bonded hydrogen atoms or alkenyl substitution (in weight%). This method allows distinguishing between all species bearing Si atoms, therefore including species with silicone bonded hydrogen and alkenyl functionalities bonded to a silicon atom. The sample (40 vol%) needs to be dissolved in deutero-chloroform (60 vol%), which contains chromium acetyl acetonate (0.05M concentration in the solvent). The solution can be measured in a 10mm NMR tube in an NMR spectrometer (400MHz). The method is called "29Si inverse gated" to allow quantitative conditions for the measurement. Parameters include a spectral width of 250 ppm, a pulse length of the 90°, a relaxation delay of 15 s, and a number of scans of 2600. After the measurement, the free induction decay is Fourier-transformed into the frequency spectrum, tetramethyl silane is used as calibration standard (0 ppm alkenyl group or silicon-bonded hydrogen atom). The peaks need to be integrated, made in relation to the mass unit of the corresponding species and the content of silicone bonded hydrogen or alkenyl functionalities bonded to a silicon atom may be calculated. The method may be applicable for all types of silicones containing methyl as principal organic functionality, and may be adapted for the calculation when other alkyl groups or functional groups are present.

[0064] FT-NIR method may be used to quantify the percentage of alkenyl groups by weight of organopolysiloxane A, by comparing the absorbance of a specific band in an infrared spectrum with the absorbance of the same band in a reference spectrum of known concentration, in the present case, the band corresponding to the carbon-carbon double bond of the alkenyl functionality. This procedure may be based on ASTM E-168 (Standard Practices for General Techniques of Infrared Quantitative Analysis) where the material to be analysed is diluted in an appropriate solvent of spectrophotometric grade. The dissolution may require mixing and may take several hours to complete. Standards of known concentrations are used as comparison for the quantification of the alkenyl functionality.

[0065] A bromine titration method may be used to quantify the percentage of silicon- bonded hydrogen atoms by weight of organopolysiloxane B, according to an estimated SiH content.

[0066] All viscosities referred to herein are taken at 25°C and standard atmospheric pressure (i.e. 101 .325 kPa), unless otherwise indicated.

[0067] The invention provides a coating composition comprising a binder, an elastomeric silicone powder formed by spray curing and a stabilizing agent or in the case of the second embodiment optionally formed by spray curing. The invention also provides coating composition as defined above wherein the binder comprises a polyurethane polymer, an acrylic polymer, a vinyl ether polymer, a poly(styrene-butadiene polymer), an alkyd resin, alkyd emulsion polymer, a phenolic resin, a polyvinyl acetate polymer, a nitrocellulose polymer, or any combination thereof. The invention also provides a coating composition as defined above, wherein the binder is provided in water.

[0068] The invention also provides a coating composition as defined above, wherein the elastomeric silicone powder comprises elastomeric silicone particles that have an average diameter of more than 10μηι by laser diffraction method. The invention further provides a coating composition as defined above, wherein the elastomeric silicone powder is made by forming a mixture of organopolysiloxane A and organopolysiloxane B, wherein organopolysiloxane A comprises alkenyl groups and organopolysiloxane B comprises silicon-bonded hydrogen atoms. The invention further provides a coating composition as defined above, wherein organopolysiloxane A comprises more than 0.5 % alkenyl groups by weight of the organopolysiloxane A, organopolysiloxane B comprises from 0.25% to 1 % silicon-bonded hydrogen atoms by weight of the organopolysiloxane B. The invention also provides a coating composition as defined above, wherein organopolysiloxane A is Q-branched. The invention also provides a coating composition as defined above, wherein the stabilizing agent comprises a functionalized silane, silazane, a wetting agent, or any combination thereof. The invention also provides a coating composition as defined above, wherein the functionalised silane comprises amino functionalized silanes, methacrylate or acrylate functionalised silanes, epoxy

functionalised silanes, vinyl functionalised silanes, ethoxy functionalised silanes, or any combination thereof. The invention also provides a coating composition as defined above, wherein the wetting agent is a silicone glycol copolymer. The invention also provides a coating composition as defined above, wherein the stabilising agent comprises trisiloxane ethoxylate and glycidoxypropyltrimethoxysilane. Weight ratio of silane to wetting agent is between 0.5% and 5.0%. The invention also provides a coating composition as defined above including from 5-15% by weight elastomeric silicone powder.

[0069] The invention further provides a method of preparing the coating composition as defined above comprising the steps of coating one or more the spray cured elastomeric silicone polymers recited in any of the preceding claims with one or more stabilizing agent recited in any of the preceding claims prior to mixing the elastomeric silicone polymers with the binder.

[0070] The present invention will now be described by way of example.

EXAMPLES

1 ) Manufacture of Elastomeric Silicone Powders

The Examples, of which compositions are given in Table 1 , were prepared as follows:

- Organopolysiloxane A is put in a beaker

- the inhibitor is added

- Organopolysiloxane B is added

- the catalyst is added

- the optional other ingredient is added

- the mixture is let in the spray curing pipes and nozzle and led to the spray curing tank to react and cure in the form of an elastomeric silicone powder.

The mixtures were prepared at room temperature (20-25°C). The inhibitor consisted of ethylene cyclohexanol, the catalyst consisted of a platinum complex. In the case of embodiment 2 the elastomeric silicone powder may be made by any suitable method however, the following is utilised as an example for both embodiments 1 and 2.

The spray curing tank was a MOBILE MINOR™ Spray dryer from GEA Process

Engineering Inc., with the following settings: an inlet temperature of 250-300°C, an outlet temperature of 130-150°C, a nozzle pressure of 1 .5 Bar.

[0071] Example 4 is a free flowing powder without agglomerates, feeling soft and cushiony. This example was used later in the examples described below for making the coating composition.

[0072] Example 5 is a free flowing powder with little agglomerates, feeling soft, not dry and cushiony.

[0073] Example 6 is a free flowing powder with little agglomerates, which does not feel dry, but slightly cushiony.

[0074] Example 7 is a free flowing powder without agglomerates, feeling soft and cushiony.

2) Manufacture of Coating Composition

[0075] The elastomeric silicone powder was manufactured according to Example 4 above. Different stabilising additives were applied to separate batches of the elastomeric silicone powder by spray coating. Each batch was mixed into separate batches of polyurethane. The polyurethane was a commercially available water based polyurethane anionic dispersion of an aliphatic polycarbonate urethane (available from Picassian or Bayer). The mixture in each batch formed a coating composition, each batch differing by the additive. The coating compositions were 90% by weight polyurethane and 10% by weight elastomeric silicone powder (coated with stabilising additive). Mixing was achieved by a dental mixer operating at 2500 rpm for 1 minute.

[0076] Each coating composition was applied to a substrate (Leneta or Film PET) by a manual bar at a thickness of 60μηι and cured for 2 minutes at 80°C in a conventional oven

3) Analysis of Manufactured Coating Compositions

[0077] In the examples below, a silicone sprayed-cured powder was made according to the example 4 and post-coated with a reactive epoxy silane (i.e.

Glycidoxypropyltrimethoxysilane) and/or a silicone polyether with HLB of 1 1 .5 (i.e.

trisiloxane ethoxylate).

[0078] The different stabilizing additives were applied on the elastomeric silicone powder in a Mi-Pro High Shear Granulator - shear devices running at 1000 rpm during 10 minutes. The different stabilizing additive treatments resulted in different batches of treated elastomeric silicone powder.

[0079] The combination of these 2 post-sprayed additives provides the best overall performance in term of matting (i.e. the lower the number, the more matte is the coating) and ease of use (i.e.; the speed of dispersion in the water based binder). Those elastomeric silicone powders were added at 10% by weight in the polyurethane dispersion. [0080] The initial value indicates the matting rating of the pure polyurethane dispersion. This is providing an indication on the highest gloss value achievable.

[0081 ] When adding the silicone powder, the matting performance is increased (i.e. the reflected light value is reduced), but not optimised.

[0082] Although the higher matting effect is obtained by the use of the silane alone, this product appears as relatively difficult to disperse properly in the polyurethane binder, although its use as the sole stabilising additive is acceptable. This inconvenience is solved by the use of the high HLB silicone glycol addition allowing an easier dispersion, whilst retaining a high level of matting of the surface; The combination of those 2

additives provide the best compromise in term of high matting performance and ease of use.

Batches Particle Glycidoxypropyl- Silicone 60° Reflected Dispersion /

size trimethoxysilane glycol light reading comments

(medium copolymer using gardner

particle fluid reflectometer

size) content (BYK Gardner

4528 micro-tri- gloss

reflectometer)

Pure polyurethane dispersion 84,7 Gloss coating

24000- 23μ No additives 38,2 Very difficult

89-02 to disperse

24000- 23μ N Y (3%) 30,2 rapid dispersion

94-01

24000- 23μ Y (3%) N 21 ,5 difficult to disperse

94-02

24000- 23μ Y (3%) Y (3%) 25 rapid dispersion

93-01