Nanopigments and polymer-mineral decoration of natural leathers

The work is devoted to the development of nanopigments based on modified montmorillonite for the formation of polymer-mineral decoration of natural leather.

The covering takes the main place among the processes of manufacturing natural leather and provides the leather with high operational and aesthetic properties. A promising direction of resource-saving and ecological leather production is the development of nanopigments on a mineral basis – modified montmorillonite, and their use for polymer-mineral finishing of leather.

An algorithm for obtaining nanopigments by successive modification of aqueous dispersions of montmorillonite with cationically active and anionically active compounds is proposed. Dispersion of montmorillonite particles with sodium carbonate and modification with hydroxochromic complexes provides a change in surface chemistry and is accompanied by structural transformations of the mineral. A high level of adsorption of anionic black and dark green dyes on the surface of particles of modified montmorillonite was established. The formation of chemical and physicochemical interactions between the dye and exchangeable cations of montmorillonite has been proven. The composition of nanopigments based on colored dispersions of montmorillonite, which are characterized by high hiding power and stability over time, has been developed.

The influence of nanopigments at a consumption of 1.5–2.0 % of montmorillonite on the physical and mechanical properties of polymer films was established, which was confirmed by a three-fold increase in the modulus of elasticity and strength limit, as well as a decrease by 11.5 % in elongation at break for polymer films. The increase in the physical and mechanical properties of polymer films is the result of physical adsorption and is associated with the formation of relatively strong coordination bonds of the polymer with the active functional centers of the montmorillonite surfaces. The mineral in the composition of nanopigments increases the physical and mechanical properties of covering films, plasticizes and structures the polymer composition, contributes to the production of leathers with high organoleptic characteristics of the front surface, namely, the volume of the network, graininess, pleasant fingerboard.

Using the method of simplex-lattice planning, the composition of covering compositions was optimized using nanopigments, rational ratios of the components of the covering composition were obtained, which ensure the formation of a polymer-mineral covering with the required level of operational properties, which is characterized by high adhesion to the leather, resistance to dry and wet friction, elasticity and strength.

The use of nanopigments in the composition of covering compositions allows to reduce the cost of covering paint for decoration, the thickness of the covering film and obtain a covering with high quality indicators in terms of the level of adhesion to dry and wet leather, resistance of the covering to repeated bending, dry and wet friction.