Binders used in Coating Colors

Both natural and synthetic binders are used in the paper coating. Binders from natural sources are used in the form of aqueous solutions and include  

Synthetic binders, which are prepared as aqueous polymer dispersions, are  

These synthetic binders commonly known as latexes are mostly modified with functional monomers such as vinyl acids, amides, acrylonitrile, etc. to improve the colloidal and rheological properties of coating color formulations and the printing and/or packaging properties of coated papers and paperboards. 

As a water-soluble substance, polyvinyl alcohol represents a special case among synthetic binders. 

The most important natural binder still in use today is starch, though it is now frequently used in combination with synthetic binders. Com starch is more common in the USA, whereas potato starch is more prevalent in Europe. Native starch containing two fractions of amylose (linear chain) and amylopectin (branched chain) is not suitable for coating paper and board because the amylose fraction tends to undergo retrogradation and the viscosity of coating colors made with native starch is too high [5]. For these reasons, only treated (i.e., depolymerized) or chemically modified starches are used. Most paper mills carry out their own starch preparations in-house. 

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