the invention pertains to a urethane topcoat coating composition comprising a polyol component , an isocyanate component and a hydroxy functional , polyether - modified polysiloxane copolymer component . the urethane is prepared from a reaction between polyols and isocyanates or isocyanurates . the -- oh of the polyol and the -- nco of the isocyanate or isocyanurate form the polyurethane linkage . when polyols such as the desmophen polyols supplied by bayer usa are combined with polyisocyanates ( e . g ., bayer &# 39 ; s desmodur polyisocyanates ) to produce polyurethane coatings , the relative amounts of the two coatings must be determined . for this , the rules of chemistry are followed . one equivalent of isocyanate reacts with one equivalent of hydroxyl such that the ratio of -- oh to -- nco is about 1 . 0 : 1 . 0 ( excluding water ). in actual practice , an excess of the isocyanate is used to allow for the potential destruction of small amounts of isocyanate by any water present . the formulations of the present invention are mixed at an isocyanate index ranging from between about 1 . 0 to about 2 . 0 . preferably , the isocyanate index of the topcoats prepared in accordance with the present invention range from between about 1 . 3 to about 1 . 9 , more preferably from between about 1 . 5 to about 1 . 8 . in order to determine the appropriate amount of isocyanate to incorporate into the topcoat composition , the following equation can be used : weight of isocyanate =(-- nco eq . wt .) ( iso . index ) ( parts of polyol /-- oh eq . wt .) for crosslinking for example , it is known that bayer &# 39 ; s desmophen a 160 has an equivalent weight of 1058 . moreover , bayer &# 39 ; s mondur cb - 75 isocyanate has an equivalent weight of 323 . using the above equation , if the isocyanate index is to be 1 . 7 , the weight of the isocyanate is 51 . 9 . with regard to the polyols which can be used when practicing this invention , they can include any material that contains a reactive hydrogen atom and that would react with the isocyanate or isocyanurate group . these materials include hydroxyl functional acrylics , hydroxyl functional polyesters , hydroxy functional polyethers , polyamines , polyamides , short oil alkyds , caster oil , epoxy resins with secondary hydroxyl groups , phenolic resins , and hydroxyl functional vinyl resins . if necessary , the vinyl resins may be used to promote adhesion . with regard to the isocyanates which can be used when practicing this invention , they can be divided into four different categories . the four types include diphenylmethane 4 , 4 &# 39 ;- diisocyanate ( mdi ), toluene diisocyanate ( tdi ), isophrone diisocyanate ( ipdi ), and hexamethylene diisocyanate ( hdi ). polyisocyanates based on hdi represent a significant category of polyisocyanates used in polyurethane coatings . specifically , those coatings which are prepared using hdi - based products typically show additional resistance to chemicals and abrasion . they also tend to exhibit desirable weathering characteristics , including retention of gloss , and resistance to yellowing and chalking . bayer &# 39 ; s desmodur n - 75 , desmodur n - 100 , and desmodur n - 3200 are examples of commercially known polyisocyanates which are based on hdi . they are polymeric materials which contain biuret groups . the hdi may be converted into a trimer containing an isocyanurate ring . such product are commercially available from bayer under the product names desmodur n - 3300 and desmodur n - 3390 . the solvent or solvent system of the topcoat composition can include any suitable solvent . examples of suitable solvents include methyl isobutyl ketone ( mibk ), methyl isoamyl ketone ( miak ), methylamyl ketone ( mak ), methylether propylene glycol acetate , and the like , and combinations thereof . the polysiloxane copolymer component of the topcoat composition prepared in accordance with the present invention is hydroxy functional and has a molecular weight ranging from between about 1 , 000 to about 10 , 000 . preferably , the molecular weight of the polysiloxane copolymer component ranges from between about 3 , 000 to about 9 , 000 , and more preferably , from between about 5 , 000 to about 8 , 000 . the polysiloxane copolymer component comprises a linear or branched polysiloxane which is modified by polyether groups attached at its ends through silicon - carbon bonds or silicone - oxygen - carbon bonds . typically , there is a balance of ethylene oxide and propylene oxide - based polyethers attached to the polysiloxane such that the polysiloxane copolymer component is dispersible in both water and solvent . any suitable polyether - modified polysiloxane copolymer can be used as the polysiloxane copolymer component when practicing the present invention . examples of such suitable polyether modified polysiloxane copolymers include those commercially available from goldschmidt chemical corp . of hopewell , va . under the product name tego ® glide 440 polyether - modified polysiloxane , tego ® glide 410 polyether - modified polysiloxane and tego ® glide 425 polyether - modified polysiloxane . the incorporation of &# 34 ; reactive diluents &# 34 ; may also be utilized to improve flow of the topcoat composition . such diluents include low molecular weight compositions with some type of a functional group ( s ) on the polymer chain and act to lower the viscosity of the primer and are then polymerized into the coating as it cures . these materials , however , may increase the cross link density of the topcoat to the extent that the topcoat becomes too brittle for use on golf balls . notwithstanding the above , upon reading the disclosure herein , one skilled in the art would be able to select such reactive diluents which best suits his / her needs . leveling additives may also be added to reduce the surface tension of the coating for improved flow . examples of leveling additives which can be used when practicing this invention include : fluorad fc - 430 fluorochemical surfactant commercially available from 3m industrial chemical products div ., st . paul , minn . and 57 additive silicone additive commercially available from dow coming corp ., midland , mich . other additives which can be included into the topcoat composition prepared in accordance with the present invention include : hindered amine u . v . stabilizers , hindered amine light stabilizers , u . v . absorbers , u . v . stabilizers , optical brighteners and de - foaming agents . in addition to the above , the topcoat composition may have pigments incorporated therein . in many instances , the pigments of choice added to the primer composition are those which will impart a white or whiter color to the golf ball . examples of such pigments include : titanium dioxide , blanc fix ( i . e ., barium sulfate ), zinc oxide , lithopone ( i . e ., a mixture of zinc oxide and barium sulfate ), and magnesium silicate . the topcoat composition prepared in accordance with the present invention can be applied over a number of different substrates . any suitable application means can be employed to apply the topcoat to the substrate . examples of application techniques include dipping , spraying and brushing . if the topcoat is applied over a golf ball , the application means of choice is spraying . typically , the topcoat is applied over substrates which are fairly rigid ( i . e ., a flexural modulus of between about 5 , 000 to about 100 , 000 ). if the substrate is the cover of a golf ball , an ionomer substrate provides for a desirable surface , although balata , synthetic balata , polyethylene , polypropylene and polyurethane also provide good surfaces . the topcoat may be applied directly to the substrate . typically , however , the topcoat is applied over a primer . the primer acts as a tie coat between the substrate and the top coat . the topcoat prepared in accordance with this invention can be applied over any suitable primer . suitable primers include clear and pigmented primers which are solvent - based or water - based . examples of particularly useful primers overwhich the topcoat of the present invention can be applied include water - base primers which include a substantially solvent - free urethane dispersion and a substantially solvent - free acrylic resin component . the solvent - free urethane component and the solvent - free acrylic component of such primers could contain as much as 15 weight percent of a solvent . typically , the solvent - free urethane component and the solvent - free acrylic component employed contain less than about 10 weight percent of a solvent , preferably , less than about 5 weight percent , and more preferably less than about 2 weight percent . notwithstanding the above , the combined solvent content of the solvent - free urethane component and solvent - free acrylic component should be such that the v . o . c . of the resulting primer composition is less than about 1 . 5 , preferably less than about 1 . 3 , and more preferably less than about 1 . 1 . the solvent - free urethane component of such primers typically has a tensile strength which ranges from between about 4 , 000 to about 9 , 000 psi . preferably , the tensile strength of the urethane component ranges from between about 5 , 000 to about 8 , 000 psi ., and more preferably from between about 6 , 000 to about 7 , 000 psi . moreover , the glass transition temperature ( t g ) the solvent - free urethane component typically ranges from between about 20 ° c . to about 50 ° c . preferably , the t g of the urethane component ranges from between about 25 ° c . to about 45 ° c ., and more preferably from between about 30 ° c . to about 40 ° c . one example of a urethane dispersion which can be used when making such water - based primers is a trimethylxylene diisocyanate ( tmxdi ) polyester polymer such as that commercially available from cytec industries , inc . of west peterson , n . j ., under the product name cydrothane ® hp - 1035 polyurethane dispersion . the solvent - free acrylic component employed when making such primers can be either made in water or in a solvent and thereafter dispersed in water . regardless of how the waterborne acrylic resin is made , it typically has a t g in the range from between about 10 ° c . to about 90 ° c ., preferably about between about 15 ° c . to about 70 ° c ., and more preferably from between about 20 ° c . to about 50 ° c . if the acrylic resin component of such primers is made in a solvent or a solvent / water mixture , a sufficient amount of the solvent should be driven off prior to dispersing it in water . the amount of solvent to be driven off depends , in part on the solvent content of the urethane component , the solvent content in the primer composition necessary to facilitate spraying and / or promote coalescence , and the desired v . o . c . of the resulting primer composition . any suitable acrylic resin which has a t g falling into the aforementioned range can be employed to make such water - based primers . for example , the aqueous dispersion of acrylic polymer fine particles used when practicing this invention can be those known per se , described in , for example , said u . s . pat . nos . 4 , 900 , 774 and 4 , 539 , 363 . an example of such an aqueous dispersion is an aqueous dispersion of acrylic polymer fine particles formed by polymerizing at least one acrylic monomer and , if required , another copolymerizable monomer in the presence of a nonionic surface active agent such as polyoxyethylenenonyl - phenyl ether , an anionic surface active agent such as polyoxyethylenealkylallyl ether sulfuric acid ester , and a dispersion stabilizer such as a water - soluble resin having an acid value of about 20 to 150 and a number average molecular weight of about 5 , 000 to 30 , 000 , for example , an acrylic resin , said particle having an average particle size of usually about 0 . 02 to about 1 micrometer , especially 0 . 03 to 0 . 5 micrometer . examples of the acrylic monomer subjected to polymerization are ( meth ) acrylic acid ; carboxyalkyl ( meth ) acrylates such as 2 - carboxyethyl ( meth ) acrylate ; alkyl ( meth ) acrylates such as methyl ( meth ) acrylate , ethyl ( meth ) acrylate , propyl ( meth ) acrylate , propyl ( meth ) acrylate , n - butyl ( meth ) acrylate , isobutyl ( meth ) acrylate and 2 - ethylhexyl ( meth ) acrylate ; hydroxyalkyl ( meth ) acrylates such as hydroxyethyl ( meth ) acrylate , hydroxypropyl ( meth ) acrylate and hydroxybutyl ( meth ) acrylate ; ( meth ) acrylamides such as ( meth ) acrylamide , n - propoxymethyl ( meth ) acrylamide and n - butoxymethyl ( meth ) acrylamide ; and glycidyl ( meth ) acrylate . they are used either singly or in combination . examples of the other monomer copolymerizable with the acrylic monomer are alpha beta - ethylenically unsaturated carboxylic acids such as maleic acid , funaric acid , itaconic acid and a half ester of maleic acid or fumaric acid , vinyl aromatic compounds such as styrene , vinyl toluene and alpha - methylstyrene , vinyl acetate , and ( meth ) acrylonitrile . moreover , a polyfunctional monomer can be used in a small amount , if required , to crosslink the formed polymer fine particles . examples of the polyfunctional monomer are divinylbenzene , ethylene glycol di ( meth ) acrylate , 1 , 6 - hexane di ( meth ) acrylate , trimethylolpropane di ( meth ) acrylate , allyl ( meth ) acrylate , and triacrylic acid trimethylolpropane . as the aqueous dispersion of acrylic polymer fine particles used in such primers , an aqueous dispersion prepared by a multistage polymerization method is also available . for example , a multistage polymerization emulsion formed by first emulsion - polymerizing the above acrylic monomer not containing or containing a small amount of an alpha beta - ethylenically unsaturated acid , and then copolymerizing an acrylic monomer containing a large amount of an alpha beta - ethylenically unsaturated acid is thickened by neutralization with a neutralizing agent , and is therefore desirable from the aspect of coatability . examples of the neutralizing agent are ammonia and water - soluble amino compounds such as monoethanolamine , ethylamine , dimethylamine , diethylamine , triethylamine , propylamine , dipropylamine , isopropylamine , diisopropylamine , triethanolamine , butylamine , dibutylamine , 2 - ethylhexylamine , ethylenediamine , propylenediamine , ethylethanolamine , dimethylethanolamine , diethylethanolamine , 2 - amino - 2 - methylpropanol , and morpholine . of these , triethylamine , dimethylethanolamine and 2 - amino - 2 - methylpropanol are especially preferable . in the aqueous dispersion of acrylic polymer fine particles used in such primers , dispersed particles may be crosslinked when stress is laid upon properties such as mechanically stability , storage stability , etc . the crosslinking method can be a method known as per se in which a polyfunctional monomer such as divinylbenzene or a monomer comprising a combination of ( meth ) acrylic acid and glycidyl ( meth ) acrylate is contained in a monomer component that forms particles . moreover , the acrylic polymer fine particles are themselves required to have good finish appearance , excellent water resistance , etc . of the coated film . good finish appearance can be achieved by using a relatively large amount of unsaturated acid monomer such as ( meth ) acrylic acid . moreover , the use of a long - chain alkyl ester of ( meth ) acrylic acid is useful to improve water resistance the amount of the solvent - free urethane component present in such low v . o . c . primers typically ranges from between about 10 to about 90 weight percent , while the amount of the solvent - free acrylic component ranges from between about 90 to about 10 weight percent . preferably , the amount of the solvent - free urethane component ranges from between about 20 to about 80 weight percent , while the amount of the solvent - free acrylic component ranges from between about 80 to about 20 weight percent . more preferably , the amount of the solvent - free urethane component ranges from between about 30 to about 70 weight percent , while the amount of the solvent - free acrylic component ranges from between about 70 to about 30 weight percent . even more preferably , the amount of the solvent - free urethane component ranges from between about 40 to about 60 weight percent , while the amount of the solvent - free acrylic component ranges from between about 60 to about 40 weight percent . in instances where the ratio of the urethane component to the acrylic component ranges from between about 10 : 90 to about 30 : 70 , it may be necessary to add additional solvent to the primer composition to promote coalescence . the amount of additional solvent which may be necessary will depend upon the amount of solvent , if any , present in the urethane component and the acrylic component . notwithstanding the above , the amount of additional solvent added , if any , should be such that the v . o . c . of the resulting primer composition is less than about 1 . 5 , preferably less than about 1 . 3 , and more preferably less than about 1 . 1 . if additional solvent is added to the primer composition , any solvent can be employed which is compatible with the urethane and acrylic components of the primer composition . one example of a particularly useful solvent which can be employed is 2 -( 2 - butoxy ethoxy ) ethanol commercially available from union carbide under the product name butyl carbitol ®. as with the topcoat compositions prepared in accordance with the present invention , the incorporation of &# 34 ; reactive diluents &# 34 ; may also be utilized with the primer to improve flow of the primer composition . such diluents include low molecular weight compositions with some type of a functional group ( s ) on the polymer chain and act to lower the viscosity of the primer and are then polymerized into the coating as it cures . these materials , however , may increase the cross link density of the primer to the extent that the primer becomes too brittle for use on golf balls . notwithstanding the above , upon reading the disclosure herein , one skilled in the art would be able to select such reactive diluents which best suits his / her needs . leveling additives may also be added to the primer to reduce the surface tension of the coating for improved flow . examples of leveling additives which can be used when practicing this invention include : fluorad fc - 430 fluorochemical surfactant and 57 additive silicone . other additives which can be included into the primer composition prepared in accordance with the present invention include : hindered amine u . v . stabilizers , hindered amine light stabilizers , u . v . absorbers , u . v . stabilizers , optical brighteners and de - foaming agents . in addition to the above , the primer composition may have pigments incorporated therein . in many instances , the pigments of choice added to the primer composition are those which will impart a white or whiter color to the golf ball . examples of such pigments include : titanium dioxide , blanc fix ( i . e ., barium sulfate ), zinc oxide , lithopone ( i . e ., a mixture of zinc oxide and barium sulfate ), and magnesium silicate . if used , the primer may be applied directly to the substrate . however , in some instances , a pretreatment to the surface , or an additional additive to the primer , may be necessary . for example , in some instances where the substrate overwhich the primer is applied is an ionomeric resin ( e . g ., surlyn ®), it is preferred to use an adhesion promoter . however , in other instances , such as those where the substrate overwhich the primer is applied is balata , a polyurethane or a polyolefin , adhesion promoters are typically not required . notwithstanding the above , if employed , the adhesion promoter is generally present in an amount ranging from between about 0 . 5 to about 20 weight percent , preferably , from between about 1 to about 15 weight percent , and more preferably from between about 1 . 5 to about 10 weight percent . one example of a particularly useful adhesion promoter which can be used when practicing this invention is the polyfunctional aziridine crosslinker commercially available from zeneca resins of wilmington , mass ., under the product name of crosslinker cx - 100 . any suitable application means can be employed to apply the primer to the substrate . examples of application techniques include dipping , spraying and brushing . if the primer is applied over a golf ball , the application means of choice is spraying . the adhesion of the coating to the golf ball and the coating &# 39 ; s durability is tested through the use of the following &# 34 ; hit test &# 34 ; and &# 34 ; tumble test .&# 34 ; in the &# 34 ; hit test ,&# 34 ; a standard indoor hitting machine , as known to one of ordinary skill in the art , is employed with catch nets , catch bins and return gutters . the arm of the pendulum impacts the ball at approximately 90 miles per hour . the &# 34 ; tumble test &# 34 ; is designed to gauge abrasion / scuff resistance and to replicate the wear and abrasion characteristics of golf balls supplied for use on driving ranges (&# 34 ; range balls &# 34 ;). this test employs a 2 - gallon porcelain jar and jar mill manufactured by norton . the abrasion agents are e252 alundum ( granule size sm8 ) and small marble chips . an scoop is used to measure the amounts of abrasion agents , with 1 scoop of alundum weighing about 1 . 8 pounds and 1 scoop of small marble chips weighing about 1 . 7 pounds . initially , 2 scoops of alundum chips and 2 scoops of marble chips are placed in the jar . then , 24 golf balls are placed in the jar , followed by 2 more scoops of alundum and 2 more scoops of marble chips . the jar mill is turned on and allowed to run for approximately 3 hours . the balls are then removed , rinsed with water , brushed with a nessler tube brush , and dried with towels . the examples which follow are intended to assist in a further understanding of this invention . particular materials employed , species and conditions are intended to be illustrative of the invention . the examples which follow show the preparation of topcoat compositions encompassed by the present invention , the application of topcoat compositions over golf balls , the application of top coats over the primer compositions , and the adhesion and durability testing of various primer / top coat systems . in this example , a substantially solvent - free acrylic latex formulation of about 40 % solids was prepared . the solids comprised about 40 weight percent methyl methacrylate , about 33 weight percent 2 - ethylhexyl acrylate , about 25 weight percent styrene and about 2 weight percent acrylic acid . more specifically , the following enumerated ingredients were added to a 5 liter round bottom flask equipped with an air driven stirrer : ( 1 ) deionized water , 158 . 5 grams , ( 2 ) 100 % active sodium dodecyl benzene sulfonate ( commercially available from rhone - poulenc under the product name siponate ® ds - 10 ), 1 . 6 grams , and ( 3 ) sodium bicarbonate , 2 grams . this charge was heated to 80 ° c . under a blanket of nitrogen . at 80 ° c ., the following solution was added to the flask : ( 1 ) deionized water , 22 grams , ( 2 ) ammonium persulfate , 6 grams , and ( 3 ) pre - emulsion solution , 68 . 1 . the pre - emulsion solution included : ( 1 ) deionized water , 685 . 7 grams , ( 2 ) siponate ® ds - 10 , 6 . 4 grams , ( 3 ) methyl methacrylate , 640 grams , ( 4 ) ethyl hexyl acrylate , 528 grams , ( 5 ) styrene , 400 grams , and ( 6 ) acrylic acid , 32 grams . once the addition of these components was complete , the reaction was held at 80 ° c . for 15 minutes to form a seeded polymerization . thereafter , while the temperature of the flask was maintained from between 80 ° c . to 85 ° c ., the remaining pre - emulsion solution was added to the flask over a 3 hour period of time . upon completion of the pre - emulsion feed , the reaction was maintained at a temperature range from between 80 ° c . to 85 ° c . for two additional hours . the reaction was then cooled to 35 ° c . and neutralized to a ph of about 9 with the addition of 32 grams of concentrated ammonium hydroxide . the resulting latex had a non - volatile content of about 41 %, a ph of about 9 and a particle size of about 850å . this example demonstrates the preparation of a low v . o . c . primer . this primer was prepared from the components in table 1 : table 1______________________________________urethane dispersion . sup . 1 487 . 0acrylic latex . sup . 2 324 . 0acrysol rm 8 . sup . 3 1 . 9butyl carbitol 3 . 9surfonyl 104a . sup . 4 9 . 0deionized water 30 . 4 856 . 2aziridine . sup . 5 18 . 3______________________________________ . sup . 1 cydrothane hp1035 . sup . 2 prepared in accordance with example i . sup . 3 rheology modifier commercially available from rohm & amp ; haas . sup . 4 surfactant commercially available from union carbide . . sup . 5 crosslinker cx100 commercially available form zeneca resins the v . o . c . of the primer composition prepared in accordance with this example was about 0 . 4 . this example demonstrates the preparation of a low v . o . c . primer . this primer was prepared from the components in table 2 : table 2______________________________________urethane dispersion . sup . 1 320 . 4acrylic latex . sup . 2 482 . 3acrysol rm 8 1 . 9butyl carbitol 3 . 9surfonyl 104a 9 . 0deionized water 30 . 4 847 . 9aziridine 19 . 1______________________________________ . sup . 1 cydrothane hp1035 . sup . 2 prepared in accordance with example i . sup . 3 2 ( 2 - butoxy ethoxy ) ethanol commercially available from union carbide the v . o . c . of the primer composition prepared in accordance with this example was about 0 . 4 . this example demonstrates the preparation of low v . o . c . primers encompassed by the present invention . these primers were prepared from the components in table 3 : table 3______________________________________urethane dispersion . sup . 1 174 . 5 174 . 5acrylic latex . sup . 2 576 . 3 576 . 3acrysol rm 8 1 . 3 1 . 3butyl carbitol 2 . 6 27 . 6surfonyl 104a 8 . 9 8 . 9deionized water 30 . 5 30 . 5 794 . 1 819 . 1aziridine 19 . 3 19 . 3coalescence : poor goodv . o . c . level : 0 . 5 lb ./ gal 1 . 0 lb ./ gal______________________________________ . sup . 1 cydrothane hp1035 . sup . 2 prepared in accordance with example 1 as seen above , when only about 20 % solvent - free urethane dispersion was employed , additional solvent ( i . e ., about 25 lbs / 100 gallons of butyl carbitol ) was necessary to promote coalescence . this example demonstrates the preparation of white primers which contain the combination of a solvent - free urethane dispersion and an acrylic latex . the following formula is broken down into paste and liquid sections . table 4______________________________________paste portion______________________________________deionized water 65 . 3acrysol i 98 63 . 7dimethylethanol amine 2 . 9butyl carbitol 5 . 5dee - fo 806 . sup . 1 5 . 8surfonyl 104a 3 . 9titanium dioxide 259 . 0aerosil 200 . sup . 2 5 . 0 411 . 1water washout : 22 . 0total paste : 433 . 1______________________________________liquid portion______________________________________urethane dispersion . sup . 3 231 - 347 ( 40 - 60 %) acrylic latex . sup . 4 347 - 231 ( 60 - 40 %) deionized water 29 . 6butyl carbitol 3 . 3acrysol rm 8 6 . 6 617 . 5total coating : 1050 . 6______________________________________ . sup . 1 defoaming agent commercially available from ultra additives . sup . 2 rheololgy modifier commercially available from cabot corp . . sup . 3 cydrothane hp1035 . sup . 4 prepared in accordance with example i this example demonstrates the production of a polyol which was used in the preparation of urethane topcoat compositions . this example illustrates high solids compositions comprising a polyester - urethane polyol , and the method of preparing same . first , a polyester - polyol composition was prepared , as follows : the above ingredients were charged to a properly equipped reaction vessel and the resultant mixture was then heated to react in a nitrogen atmosphere . at 170 ° c . ( 338 ° f . ), there resulted the production of water of ( esterification ) reaction . with the continuous removal of the water , heating was continued to 200 ° c . ( 392 ° f .). the reaction mixture was then held at 200 ° c . ( 392 ° f .) for about 9 hours until an acid value of about 9 . 5 was attained . the resultant mixture was then cooled to a temperature of about 70 ° c . ( 158 ° f . ), discharged and analyzed . theoretical solids content was 100 percent , viscosity was 95 . 6 stokes , acid value was 9 . 5 and hydroxyl value was 319 . 5 . a polyester - urethane polyol was prepared with the above polyester - polyol composition , as follows : the above ingredients were charged to a properly equipped reaction vessel and the resultant mixture heated to react in a nitrogen atmosphere to a temperature of 110 ° c . ( 230 ° f .). the reaction mixture was held at this temperature for about 21 / 2 hours until all the isocyanate had reacted . the resultant composition was discharged and analyzed . theoretical solids content was 90 percent , acid value was 7 . 9 and hydroxyl value was 180 . 2 . this example demonstrates the production of two different urethane topcoats . the first of these topcoats had an isocyanate index of about 1 . 3 . this particular topcoat was prepared from the components of table 5 . table 5______________________________________polyol componentmethyl isobutyl ketone 236 . 0pm acetate . sup . 1 189 . 0uvitex ob . sup . 2 2 . 2cellulose acetate butyrate 10 . 1tinuvin 328 . sup . 3 9 . 4tinuvin 292 . sup . 3 4 . 1polyol . sup . 4 324 . 0 775 . 4isocyanate componentdesmodur n - 75 . sup . 5 310 . 0______________________________________ . sup . 1 methyl ether propylene glycol acetate available from dow chemical company . . sup . 2 2 , 2 ( 2 , 5 - thiophenediyl ) bis ( 5 - tert - butylbenzoxanole ) optical brightener available from ciba geigy . sup . 3 ultraviolet light absorbers . sup . 4 polyol prepared in accordance with example 6 , part 2 . sup . 5 polyisocyanate commercially available from bayer usa a first set of golf balls was coated with a high v . o . c . waterborne polyurethane / acrylic based primer . the golf balls &# 39 ; covers were made of suryln ® resin . the primer had a v . o . c . of about 2 . 8 . thereafter , the primed golf balls were coated with the first urethane topcoat prepared in accordance with this example . these coated golf balls are hereinafter referred to as &# 34 ; control balls .&# 34 ; the second of these urethane topcoats had an isocyanate index of about 1 . 7 . this particular topcoat was prepared from the components of table 6 . table 6______________________________________polyol componentmethyl isobutly ketone 228 . 0pm acetate 183 . 0uvitex ob 1 . 9cellulose acetate butyrate 17 . 3tinuvin 328 8 . 1tinuvin 292 4 . 0polyol . sup . 1 278 . 0polysiloxane polyether copolymer . sup . 2 4 . 3polypropylene glycol . sup . 3 64 . 0 788 . 6isocyanate componentdesmodur n - 75 386 . 0______________________________________ . sup . 1 polyol prepared in accordance with example 6 , part 2 . sup . 2 hydroxyfunctional linear polyethermodified polysiloxane copolymer available from goldschmidt chemical corp . under the product name of tego glide 440 . sup . 3 commercially available from ppgmazur under the product name of arcol ppg425 ( eq . wt . 425 ) a second set of golf balls was coated with a low v . o . c . waterborne polyurethane / acrylic based primer . the golf balls &# 39 ; covers were made of suryln ® resin . the primer was that which was prepared in accordance with example ii . thereafter , the primed golf balls were coated with the second urethane topcoat prepared in accordance with this example . these coated golf balls are hereinafter referred to as &# 34 ; new system balls .&# 34 ; the control and new system balls were then tested for adhesion and durability . the results were as follows : adhesion : astm 441 , adhesion for both new system and control balls was 100 %. quv test ( 1000 hrs ): astm d 4587 , no difference between new system and control balls ; also , slight yellowing with no loss of adhesion for both . hit testing : after 200 hits , no difference between new system and control balls . water immersion : after 24 hours , no difference between new system and control balls . tumble test : new system balls showed significantly less ink loss when compared to control balls . in addition to the above tests , the new system and control balls were subjected to actual trail use on a driving range in carlsbad , california for one month . the results were as follows : this example demonstrates the coating of golf balls with a low v . o . c . primer and a urethane topcoat . the golf balls &# 39 ; covers were made of suryln ® resin . the primer was that which was prepared in accordance with example ii ; and the urethane topcoat was that prepared in accordance with the first urethane topcoat of example vii . the coated golf balls were subjected to a tumble test . the results were as follows : the golf balls had poor ink durability when compared to the results of the coated golf balls in example ix . this example demonstrates the coating of golf balls with a low v . o . c . primer and a urethane topcoat . the golf balls &# 39 ; covers were made of suryln ® resin . the primer was that which was prepared in accordance with example ii ; and the urethane topcoat had an isocyanate index of about 1 . 3 . this particular topcoat was prepared from the components of table 7 . table 7______________________________________polyol componentmethyl isobutly ketone 236 . 0pm acetate 189 . 0uvitex ob 2 . 2cellulose acetate butyrate 10 . 1tinuvin 328 9 . 4tinuvin 292 4 . 1polyol . sup . 1 324 . 0polysiloxane polyether copolymer . sup . 2 4 . 3 779 . 7isocyanate componentdesmodur n - 75 310 . 0______________________________________ . sup . 1 polyol prepared in accordance with example 6 , part 2 . sup . 2 hydroxyfunctional linear polyethermodified polysiloxane copolymer available from goldschmidt chemical corp . under the product name of tego glide 440 the coated golf balls were subjected to a tumble test . the results were as follows : the golf balls had very good ink durability , especially when compared to the results of the coated golf balls in example viii . this example demonstrates the coating of golf balls with a low v . o . c . primer and a urethane topcoat . the golf balls &# 39 ; covers were made of suryln ® resin . the primer was that which was prepared in accordance with example ii ; and the urethane topcoat had an isocyanate index of about 1 . 3 . this particular topcoat was prepared from the components of table 8 . table 8______________________________________polyol componentmethyl isobutly ketone 228 . 0pm acetate 183 . 0uvitex ob 1 . 9cellulose acetate butyrate 17 . 3tinuvin 328 8 . 1tinuvin 292 4 . 0polyol . sup . 1 278 . 0polysiloxane polyether copolymer . sup . 2 4 . 3polypropylene glycol . sup . 3 64 . 0 788 . 6isocyanate componentdesmodur n - 75 295 . 0______________________________________ . sup . 1 polyol prepared in accordance with example 6 , part 2 . sup . 2 hydroxyfunctional linear polyethermodified polysiloxane copolymer available from goldschmidt chemical corp . under the product name of tego glide 440 . sup . 3 commercially available from ppgmazur under the product name of arcol ppg425 ( eq . wt . 425 ) the coated golf balls were subjected to a tumble test . the results were as follows : the golf balls had excellent ink durability , especially when compared to the results of the coated golf balls in examples viii and ix . this example demonstrates the preparation of a urethane topcoat which relatively fast at relatively low temperatures . a first urethane topcoat had an isocyanate index of about 1 . 7 . this particular topcoat was prepared from the components of table 9 . table 9______________________________________polyol componentmethyl isobutly ketone 228 . 0pm acetate 183 . 0uvitex ob 1 . 9cellulose acetate butyrate 17 . 3tinuvin 328 8 . 1tinuvin 292 4 . 0polyol . sup . 1 278 . 0polysiloxane polyether copolymer . sup . 2 4 . 3polypropylene glycol . sup . 3 64 . 0dibutyl tin dilaurate 5 . 0 793 . 6isocyanate componentdesmodur n - 75 386 . 0______________________________________ . sup . 1 polyol prepared in accordance with example 6 , part 2 . sup . 2 hydroxyfunctional linear polyethermodified polysiloxane copolymer available from goldschmidt chemical corp . under the product name of tego glide 440 . sup . 3 commercially available from ppgmazur under the product name of arcol ppg425 ( eq . wt . 425 ) a first set of golf balls was coated with the low v . o . c . primer prepared in accordance with example ii . the golf balls &# 39 ; covers were made of suryln ® resin . thereafter , the primed golf balls were coated with the first urethane topcoat prepared in accordance with this example . these coated golf balls are hereinafter referred to as &# 34 ; new system balls .&# 34 ; a second urethane topcoat was then prepared from the same components as set out in table 9 except that the second topcoat did not contain any dibutyl tin dilaurate . a second set of golf balls was then coated with the low v . o . c . primer prepared in accordance with example ii . the golf balls &# 39 ; covers were made of suryln ® resin . thereafter , the primed golf balls were coated with the second urethane topcoat prepared in accordance with this example . these coated golf balls are hereinafter referred to as &# 34 ; control balls .&# 34 ; the new system balls were heated to a temperature of 50 ° c . until the balls were no longer tacky to the touch . this curing process took approximately 1 hour . the control balls were then subjected to the same curing temperature and conditions . this latter curing process took approximately 14 hours . it is evident from the foregoing that various modifications , which are apparent to those skilled in the art , can be made to the embodiments of this invention without departing from the spirit or scope thereof . having thus described the invention , it is claimed as follows .
the invention provides a two - part urethane topcoat essentially including a polyol component , an isocyanate component and a hydroxy functional , polyether - modified polysiloxane copolymer component . the polysiloxane copolymer component has a molecular weight ranging from between about 1 , 000 to about 10 , 000 ; and is typically present in an amount ranging from between about 0 . 001 to about 10 weight percent . the equivalent weight ratio of the -- nco molecule to the -- oh molecule ranges from between about 1 . 0 to about 2 . 0 . the top coat coating prepared in accordance with the present invention has an improved the abrasion resistance , mar resistance and detergent resistance . these improved properties are especially useful for golf balls , more particularly , driving range golf balls , since it will maintain the glossy appearance and sharp outline of an ink logo printed on a golf ball for a much longer period of time , thus increasing the effective life of the golf balls .