Protein-modified Polyurethane Leather Coating Agent

As an important dressing material, leather has been been widely used. An important reason for the popularity of leathers is their good properties of warm keeping and permeability, and the later is a key factor affecting the quality and comfortableness of leathers. There are many factors that may influence the permeability of leathers, and finishing is an important one.Good finishing agent can improve the luster and beauty of leathers, rectify the uneven coloration, gloss over the tiny defect on the grain layer, improve the service performance, repair the destroyed grain layer and make a grain for the second split of leather. However, the influence of finishing on permeability of leather has not been well recognized.In this paper, a grafting modification of polyurethane (PU) finishing agent with collagen and gelatin was synthesized. The conditions of modification of this agent and its influence on permeability and other properties were discussed.As to the effect of reaction conditions on the grafting modification of polyurethane finishing agent with collagen, an optimized reaction conditions obtained were as follows: the ratio of DMPA to monomers was 5.0 wt%, reaction temperature was 80°C, and reaction time was 2.5h. The water-absorbing capacity, mechanical behaviors and water vapor permeability of the PU films with and without collagen modification was discussed. It was found that, after the modification with collagen, the elongation at break of the PU film increased up to 1401%, the water vapor permeability was 454.2 mg/10cm~2·24h, and the air permeability was 2.31mL/kPa·s. The optimized ratio of collagen to IPDI was 15-20 mol%. The polyurethane finishing agent grafting modification with collagen met the need for stabilization of emulsion, water resistance, solvent resistance and resistance to dry and wet rubbing.The effect of reaction conditions on the modification of polyurethane finishing agent with gelatin was completed with the following optimized reaction conditions: the ratio of DMPA to monomers was 5.0 wt%, reaction temperature was 80°C, and reaction time was 2.5h. It was found that, after the modification with gelatin, the elongation at break of the PU film increased up to 830.0%, the breaking stress was 3.04MPa, the water vapor permeability was 394.0mg/10cm~2·24h, and the air permeability was 1.92 mL/kPa·s. The optimized ratio of gelatin to PU was 6～10wt%. The polyurethane finishing agent grafting modification with gelatin also met the need for stabilization of emulsion, water resistance, solvent resistance and resistance to dry and wet rubbing.