Swellable clay containing water-based barrier coating and method of making the same

The process of any one of the preceding claims, wherein the binder comprises one or more of carboxylated styrene acrylate latexes, polyvinylidene chlorides, polyvinyl chlorides, starches, styrene-acrylic copolymers, styrene-maleic anhydrides, polyvinyl alcohols, polyvinyl acetates, carboxymethyl celluloses, silicones, waxes, neoprene, polyhydroxy ethers, lacquers, polylactic acids, copolymers of polylactic acid, polymers containing fluorine atoms, copolymers of acrylonitrile, and carboxylated styrene-butadiene acrylonitrile copolymers.

A process for preparing an aqueous barrier coating for a paper substrate, comprising:

• admixing a dry powder of chemically unmodified swellable clay with an aqueous polymer latex binder;
• and
• subjecting the admixture to high shear mixing under conditions such that the swellable clay disperses in the polymer latex and at least a portion of the swellable clay maintains a tactoid form to thereby form the barrier coating.

The process of any one of the preceding claims, wherein the aqueous barrier coating has a solids content of about 5% to about 55%.

The process of any one of the preceding claims, wherein high shear mixing is performed at a tip speed of about 655 ft/min to about 3300 ft/min (200 m/min to 1010 m/min).

The process of any one of the preceding claims, wherein the dry powder of chemically unmodified swellable clay comprises less than 12% moisture.

The process of any one of the preceding claims, wherein high shear mixing is performed using a Cowles mixer, a sonicator, or a rotor-stator mixer.

The process of any one of the preceding claims, wherein the high shear mixing is performed under conditions to exfoliate the swellable clay while dispersing the swellable clay in the binder such that the swellable clay present in the coating has a shape factor of above 4 as measured by a ratio of the Horiba d50 measured with static light scattering to the Zave particle size measured with dynamic light scattering.

The process of any one of the preceding claims, wherein the dry powder of chemically unmodified swellable clay is added to the binder in an amount of about 1 wt % to about 20 wt % based on the total weight of the admixture on a dry weight basis.

The process of any one of the preceding claims, wherein the admixture is free of dispersants.

The process of any one of the preceding claims, wherein the chemically unmodified swellable clay is a chemically and mechanically unmodified swellable clay.

An aqueous barrier coating, comprising:

• chemically unmodified swellable clay dispersed in a binder, wherein the swellable clay is dispersed under high shear conditions such that at least a portion of the swellable clay is present in the form of tactoids, wherein the binder is water-based or water-soluble.