Coated fiber cement article with crush resistant latex topcoat

Abstract

A coated fiber cement article in the form of an unattached fiber cement board roofing tile or roofing slate substrate having a first major surface at least a portion of which is covered with a crush resistant final topcoat composition comprising a multistage latex polymer.

We claim: 
     
         1 . A coated fiber cement article comprising an unattached fiber cement board roofing tile or roofing slate substrate having a first major surface at least a portion of which is covered with a crush resistant final topcoat composition comprising a multistage latex polymer. 
     
     
         2 . The article of  claim 1 , wherein the multistage latex polymer has a gradient Tg. 
     
     
         3 . The article of  claim 1 , wherein the multistage latex polymer comprises at least one soft stage having a Tg less than about 40° C. and at least one hard stage having a Tg greater than about 40° C. 
     
     
         4 . The article of  claim 1 , wherein the multistage latex polymer comprises at least one soft stage having a Tg between about −15 and about 15° C. and at least one hard stage having a Tg between about 60 and about 105° C. 
     
     
         5 . The article of  claim 1 , wherein the multistage latex polymer comprises about 50 to about 90 wt. % soft stage polymer morphology and about 10 to about 50 wt. % hard stage polymer morphology based on the total multistage latex polymer weight. 
     
     
         6 . The article of  claim 1 , wherein the multistage latex polymer has a soft stage Tg such that the topcoat composition will coalesce at a Minimum Film Forming Temperature (MFFT) between about 0 and about 55° C. without requiring more than 10% VOCs for acceptable film formation. 
     
     
         7 . The article of  claim 1 , wherein the topcoat composition has a minimum film forming temperature less than about 20° C. 
     
     
         8 . The article of  claim 1 , wherein the topcoat composition comprises at least about 10 wt. % multistage latex polymer. 
     
     
         9 . The article of  claim 1 , wherein the multistage latex polymer is functionalized. 
     
     
         10 . The article of  claim 1 , wherein the multistage latex polymer comprises acetoacetyl functionality. 
     
     
         11 . The article of  claim 1 , wherein the multistage latex polymer was formed from one or more ethylenically unsaturated monomers and less than about 20 wt. % styrene was used to form the multistage latex polymer based upon the total weight of such ethylenically unsaturated monomers used to form such polymer. 
     
     
         12 . The article of  claim 1 , wherein the topcoat composition includes less than 7 wt. % volatile organic compounds. 
     
     
         13 . The article of  claim 1 , wherein the topcoat composition includes less than 4 wt. % volatile organic compounds. 
     
     
         14 . The article of  claim 1 , wherein the topcoat composition further comprises at least about 1 wt. % low VOC coalescent and has a pigment volume concentration less than 45%. 
     
     
         15 . The article of  claim 1 , wherein the topcoat has a Crush Resistance value of at least 3 when two face-to-face coated profiled or embossed fiber cement board substrates are subjected to a pressure of about 6 kg/cm 2 . 
     
     
         16 . The article of  claim 1 , wherein the topcoat will change less than 10 Macadam units following a 5 year vertical exterior exposure in Florida. 
     
     
         17 . The article of  claim 1 , wherein the topcoat has a chalk rating not less than 5 when evaluated according to ASTM D 4214 Test Method A using a 5 year vertical exterior exposure in Florida. 
     
     
         18 . The article of  claim 1 , wherein the substrate comprises an unattached fiber cement board roofing tile. 
     
     
         19 . The article of  claim 1 , wherein the substrate comprises an unattached fiber cement board roofing slate. 
     
     
         20 . The article of  claim 1 , further comprising a pallet loaded with one or more stacks containing a plurality such roofing tiles or slates.