Merchandisers having anti-fog coatings and methods for making the same

Abstract

A variety of refrigerators and merchandisers having glass or plastic substrates that are substantially fog-resistant are provided. For example, refrigerator doors having a substantially transparent substrate including an anti-fog coating on at least a portion thereof are provided. The portion of the substrate may substantially not fog when the portion has an initial surface temperature and is then exposed to a moist air ambient with a dewpoint temperature equal to or greater than the surface temperature for a period of time. The surface temperature may be less than about 0° C. and the period of time may be greater than about 6 seconds.

1 . A method of manufacturing a refrigerator door having a substantially transparent substrate, the method comprising the acts of
 mixing a blocked isocyanate with a polyol to form a mixture;   applying the mixture to at least a portion of the substantially transparent substrate; and   curing the mixture to form a coating,   wherein the substrate is part of a refrigerator door or is used to manufacture a refrigerator door.   
   
   
       2 . The method of  claim 1 , wherein the blocked isocyanate comprises at least one of hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, bis(methylcyclohexyl) diisocyanate, oxime blocked hexamethylene diisocyanate, diethyl malonate blocked toluene diisocyanate, 3,5 dimethyl pyrazole blocked toluene diisocyanate, and combinations thereof. 
   
   
       3 . The method of  claim 1 , wherein the blocked isocyanate comprises toluene diisocyanate blocked with 3,5 dimethyl pyrazole. 
   
   
       4 . The method of  claim 1 , wherein the isocyanate comprises at least one of a biuret, diisophorone diisocyanate, hexamethylene diisocyanate, isocyanurate of a diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, bis(methylcyclohexyl)diisocyanate, oxime blocked hexamethylene diisocyanate, diethyl malonate blocked toluene diisocyanate, toluene diisocyanate blocked with 3,5 dimethyl pyrazole and combinations thereof. 
   
   
       5 . The method of  claim 1 , wherein the isocyanate includes a blocking agent component including at least one of oxime, pyrazole, phenol and combinations thereof. 
   
   
       6 . The method of  claim 1 , wherein curing the mixture is performed at about 80° C. to about 180° C. 
   
   
       7 . The method of  claim 1 , wherein curing the mixture is performed at about 125° C. to about 135° C. 
   
   
       8 . The method of  claim 1 , wherein curing the mixture takes place for at least about 10 minutes. 
   
   
       9 . The method of  claim 1 , wherein the polyol comprises at least one of polyethylene glycol, polypropylene glycol, block polymers thereof, and combinations thereof. 
   
   
       10 . The method of  claim 1 , wherein the polyol has a molecular weight equal to or between about 600 and about 800. 
   
   
       11 . The method of  claim 1 , wherein the polyol has a molecular weight equal to or between about 800 and about 1500. 
   
   
       12 . The method of  claim 1 , wherein the polyol has a molecular weight equal to or between about 1500 to about 4600. 
   
   
       13 . The method of  claim 1 , wherein the polyol has a molecular weight equal to or greater than about 4600. 
   
   
       14 . The method of  claim 1 , wherein the mixture is substantially free of cross-linkers. 
   
   
       15 . The method of  claim 1 , the mixture is substantially free of surfactants. 
   
   
       16 . The method of  claim 1 , wherein a catalyst is added to the mixture during mixing. 
   
   
       17 . The method of  claim 1 , wherein the mixture comprises about 10 to about 85 percent polyol and about 15 percent to about 90 percent by weight isocyanate. 
   
   
       18 . The method of  claim 17 , wherein the mixture further comprises at least one of a catalyst, solvent, rheological agent, and combination thereof. 
   
   
       19 . The method of  claim 1 , wherein the refrigerator door comprises an additional substrate having a low-emissivity surface or a low-emissivity coating thereon. 
   
   
       20 . The method of  claim 19 , wherein the low-emissivity surface or coating does not emit radiation above about 0.7 microns. 
   
   
       21 . The method of  claim 19 , wherein the low-emissivity surface or coating does not emit radiation between about 0.7 and about 2.7 microns. 
   
   
       22 . The method of  claim 19 , wherein the low-emissivity surface has a visible transmittance of about 70% to about 90%. 
   
   
       23 . The method of  claim 1 , wherein the coating comprises a hydrophobic surface having a surface tension and a hydrophilic interior having a hydrophilicity. 
   
   
       24 . The method of  claim 23 , wherein the surface tension is less than about 30 dynes/cm. 
   
   
       25 . The method of  claim 23 , wherein the hydrophilicity is between about 20% weight gain and 150% weight gain when the coating is immersed in water for about 96 hours at about 20 to 25° C. 
   
   
       26 . The method of  claim 1 , wherein the coating has a taber haze of less than about 10% at 100 cycles with 500 gram load and a CS-10F load using ASTM D 4060 testing. 
   
   
       27 . The method of  claim 1 , wherein substantially no fog forms on the portion of the substrate having the coating thereon when the substrate has an initial surface temperature of less than about 0° C., and is then exposed to a moist air ambient with a dewpoint temperature equal to or greater than the surface temperature for a period of time, the period of time being greater than about 6 seconds. 
   
   
       28 . The method of  claim 27 , wherein the period of time is greater than five minutes. 
   
   
       29 . The method of  claim 1 , wherein substantially no fog forms on the portion of the substrate having the coating thereon when the substrate has an initial surface temperature of less than about −18° C., and is then exposed to a moist air ambient with a dewpoint temperature equal to or greater than the surface temperature for a period of time, the period of time being greater than about 6 seconds. 
   
   
       30 . The method of  claim 29 , wherein the period of time is greater than five minutes. 
   
   
       31 . The method of  claim 1 , wherein the coating comprises a surfactant in an amount of less than about 3%.