Water-based coating compositions and systems with improved sag resistance and related methods

Abstract

The present invention provides a water-based coating and/or coating system that can be used to form sag resistant wet layers or coatings on a wide range of substrates. The coating system is particularly effective for protecting metal-containing substrates, such as intermodal cargo containers, against corrosion. As an overview, the present invention provides water-based compositions suitable to form primer coats on substrates. Desirably, the primer incorporates a high level of one or more CAS agents for excellent sag resistance while drying in a broad range of relative humidity environments. Alternatively, modifications can be made to control temperature and humidity during spray application and drying as a way to increase sag resistance of the coating.

What is claimed is: 
     
         1 . A shipping container, made by a process comprising the steps of:
 providing a five-sided container including an open side, a first wall opposite the open side, and four side walls connected to the first wall, wherein the side walls extend in a first direction with respect to the first wall, and wherein each of the first wall and the four side walls have an interior surface;   applying a water-based paint to the interior surfaces of the first wall and the side walls of the container; and   forcing heated air into the open side of the container to at least partially dry the paint on the interior surfaces of the container, wherein the heated air is directed such that the heated air:
 travels in a second direction opposite to the first direction to contact an interior surface of the first wall and flows in a third direction and a fourth direction thereover, wherein the third direction and the fourth direction are substantially opposite one another and substantially normal to the second direction and the first direction; 
 flows in the first direction along the interior surfaces of the walls of the container; and 
 exits the container. 
   
     
     
         2 . The shipping container of  claim 1 , wherein the interior surface of the first wall of the container and the interior surface of the side walls of the container intersect to form edge regions, wherein the interior surfaces of the first wall of the container and the interior side walls of the container intersect to form corner regions, and wherein the heated air contacts at least one edge region or at least one corner region of the container. 
     
     
         3 . The shipping container of  claim 1 , wherein the heated air is forced into the container for less than about 20 minutes. 
     
     
         4 . The shipping container of  claim 1 , wherein applying a water-based paint comprises:
 applying at least one primer coat to the interior surfaces of the container, wherein the primer coat comprises a dried coating prepared from a coating composition including
 an aqueous carrier; 
 a first resin component comprising polyvinylidene chloride in admixture with the aqueous carrier; and 
 one or more fillers; and 
   optionally, applying at least one topcoat over the primer coat.   
     
     
         5 . The shipping container of  claim 1 , wherein the heated air has a temperature of about 50 to about 200° C. 
     
     
         6 . The shipping container of  claim 1 , wherein the heated air travels in the second direction and enters the open side of the container at a velocity sufficient to provide substantially laminar flow along the interior surface of the first wall of the container. 
     
     
         7 . The shipping container of  claim 1 , wherein the heated air has a velocity of about 0.1 to about 10 meters/second. 
     
     
         8 . A shipping container made by a process comprising the steps of:
 providing a five-sided container including an open side, a first wall opposite the open side, and four side walls connected to the first wall, wherein the side walls extend in a first direction with respect to the first wall, wherein each of the first wall and the four side walls have an interior surface, and wherein the interior surfaces of the first wall of the container and the interior surfaces of at least two side walls of the container intersect to form corner regions;   applying a water-based paint to the interior surfaces of the first wall and the side walls of the container; and   allowing the container to dry in an environment having a relative humidity in the range of up to about 95% by forcing heated air into the open side of the container for about 10 to 30 minutes, wherein the heated air is directed such that the heated air:
 travels in a second direction opposite to the first direction and enters the open side of the container at a velocity sufficient to provide substantially laminar flow along the interior surface of the first wall of the container, and flows in a third direction and a fourth direction thereover, wherein the third direction and the fourth direction are substantially opposite one another and substantially normal to the second direction and the first direction; 
 flows in the first direction along the interior surfaces of the walls of the container; and 
 exits the container. 
   
     
     
         9 . The shipping container of  claim 8 , wherein the relative humidity is in the range of 50% to 85%. 
     
     
         10 . The shipping container of  claim 8 , wherein the relative humidity is in the range of 50% to 75%. 
     
     
         11 . A shipping container made by a process comprising the steps of:
 providing a five-sided container including an open side, a first wall opposite the open side, and four side walls connected to the first wall, wherein the side walls extend in a first direction with respect to the first wall, and wherein each of the first wall and the four side walls have an interior surface;   applying a water-based paint to the interior surfaces of the first wall and the side walls of the container in process conditions modified to control humidity and temperature, wherein the water-based paint comprises an aqueous carrier; a first resin component comprising polyvinylidene chloride in admixture with the aqueous carrier; one or more fillers; and one or more CAS agents dispersed in the aqueous carrier, wherein the one or more CAS agents are present in a sufficient amount to provide the water-based paint with sag resistance at 80% relative humidity and 25° C. that is at least 60% of the sag resistance of the water-based paint at 50% relative humidity and 25° C.; and   forcing heated air into the open side of the container to at least partially dry the paint on the interior surfaces of the container, wherein the heated air is directed such that the heated air (i) travels in a second direction opposite to the first direction to contact an interior surface of the first wall and flows in a third direction and a fourth direction thereover, wherein the third direction and the fourth direction are substantially opposite one another and substantially normal to the second direction and the first direction; (ii) flows in the first direction along the interior surfaces of the walls of the container; and (iii) exits the container.   
     
     
         12 . The shipping container of  claim 11 , wherein the one or more CAS agents comprise hydrophilic clay and are present in an amount greater than 0.12 kg per 100 L of the water-based paint. 
     
     
         13 . The shipping container of  claim 11 , wherein the one or more CAS agents comprise bentonite. 
     
     
         14 . The shipping container of  claim 11 , wherein the one or more CAS agents have average particle size less than 1 micrometer. 
     
     
         15 . The shipping container of  claim 11 , wherein the water-based paint is substantially free of associative sag resistant agent(s).