"Examples of the polymer binders include cellulose derivatives such as methyl cellulose, ethyl cellulose and cellulose triacetate; homopolymers and copolymers of acrylic monomers such as acrylic acid, methacrylic acid, acrylic esters and methacrylic esters; vinyl polymers such as poly (vinyl butyral), poly (vinyl pyrrolidone) and poly (vinyl formal); styrene polymers such as polystyrene; rubber pol" . . . .