Brilliancy: thy name is CTOP-AMC

19 July 2007

Sudarshan Kumar Mishra, senior technical manager, C & E Ltd, India, highlights the benefits of a finely dispersed casein product that improves the finish of leathers. CTOP-AMC is an alkaline anionic solution of very finely dispersed casein, which yields a highly transparent and medium hard film with a requisite resistance to water. The film yielded by CTOP-AMC gives a mirror like surface and a microscope shows the appearance of tiny mirror-like plane surfaces separated about 0.3mm apart, which is close to the average resolving power of human sight. With an active ingredient of 11+-1% and a 10% solution in demineralized water it has a pH of 7-8.5. CTOP-AMC is designed to take into account the fact that leather is a flexible material and has inherent stretch. Plasticization has accordingly been engineered to avoid the possibility of deformation or crack. As a result, CTOP-AMC shows unparalleled elasticity when compared with the group of various medium hard proteins available to the leather finishing industry globally. Adhesion: A portion of CTOP-AMC solution rapidly penetrates the leather and sets, through evaporation, giving rise to a rigid anchorage. The solution contains both amino and carboxyl groups as depicted in the basic chain structure (Figure 1) which shows strong adhesion to the leather. The dipolar molecules migrate between the season and leather interfaces and orient in such a way that the groups bridge the season and the leather. This increases the adhesion. Mild snuffing even with 900 or 1,000 emery has a positive influence on the anchorage as the contact area is substantially enhanced and the oily substances, if any, on the leather surface are removed. Treatment of the leather surface with a cationic base from C & E Ltd has a positive effect on bondage as an electrovalent linkage is established with the negatively charged molecules of CTOP-AMC. Holding Power: Even when CTOP-AMC is not the main binding medium in the season, incorporation of even 5% in the finish displays an increase in the binding of non-bonding ingredients like pigments, fillers etc. In protein or pu-protein finishes, where higher parts of CTOP-AMC are used, the later remains well embedded in the finish film which is further strengthened by forming insoluble complexes when in contact with polyaldehydes such as CFIX-AFB and CFIX-APF. The rub resistance increases satisfactorily on ageing. Milling endurance: Unlike many other binders available in the market, CTOP-AMC shows good resistance to dry milling. This could be achieved with the help of requisite elasticity and the strong adhesion it possesses. This renders CTOP-AMC as an important component for lightly finished natural dry milled leathers. Thickness: The film is very thin which has numerous advantages with regards to clarity, extensibility, feel etc. A finish coat having CTOP-AMC as the main binding constituent remains light and helps in getting a warm smooth handle. Gloss: The drying of CTOP-AMC on leather is uniform and results in a smooth glossy film, which remains well plasticized. The possibilities of light scattering, either due to wrinkling or minute hair cracks on the film surface, are eliminated. When used in a top finish, the chemistry of CTOP-AMC can be mechanically smoothed giving rise to major light reflection. Resistance to water: The film yielded by CTOP-AMC is itself insoluble in water and the sphere of resistance is widened when the film undergoes polyaldehydic treatment. There's no swelling observed and, if any dull area occurs after water contact, shine and colour depth are regained when the area is polished or brushed again. Mechanical resistance: Certain leathers such as kid and calf require polishing or glazing to achieve a high degree of gloss. As the moisture content of the film goes down during drying, the melting point goes up and the thermal resistance is considerably enhanced. After good drying, the film of CTOP-AMC can withstand very high temperature ironing and friction giving rise to still higher levels of gloss. Not only is gloss imparted to the surface but also the grain is flattened by mechanical pressure. The plasticizers in CTOP-AMC ensure smooth gliding of the machine roller and avoid any unwanted dragging. Very good behaviour is, thus, observed on felt polishing, stone polishing, glazing, heated Rotopress, Setilux, Finiflex or Contilux etc. Embossability: CTOP-AMC assists the finish to get an uncut and clear print impression however small the print size may be.

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