From Leather Wastes back to Leather Manufacturing: The Development of New Bio-Based Finishing Systems

Abstract

The leather industry is currently between two opposing paths: on the one hand, recent legislative trends in terms of the eco-sustainability of industrial processes are leading leather manufacturing towards the development of cleaner production methods; on the other hand, the spread of new alternative materials to leather is driving the leather industry to improve its competitiveness by developing new innovative and high-quality products. Leather finishing is one of the most important phases of leather production, and is capable of improving its quality and organoleptic properties. However, this phase is characterized by the use of polluting chemical products, such as volatile organic compounds, potentially toxic crosslinking agents, and hardly biodegradable resins. In this context, this research work aims to develop a finishing formulation capable of giving leather the durability and quality properties required by the market, while at the same time, being eco-sustainable. Specifically, the aim of the present work is to suggest a new finishing formulation in terms not only of green technology but also of a circular production flow, by recovering solid leather wastes. The developed finishing system is based on the application of collagen, extracted from tanned wastes through an enzymatic treatment, to be cross-linked and bound to the leather surface. This new bio-based leather finish is compared to a resin-based leather finish, and shows the same quality standards as those requested by the market.

The Effects of Differences Colorant Used in Finishing on the Quality of Pull-Up Mill Leather

“…The addition of collagen and casein to polyurethanes results in finishing films that are noticeably more transparent-a desirable attribute for leather finishing. In addition, films that are composed only of collagen and casein exhibit intriguing characteristics while having higher hardness levels [12]. Pigment pastes resemble homogeneous, viscous fluids, and their dry substance percentages suggest that they are concentrated pastes in nature [13].…”

Development of a New Collagen Gel Product for Leather Finishing

“…The devised finishing system revolves around applying collagen, extracted from tanned wastes through enzymatic treatment, to cross-link and adhere to the leather surface. The resulting biobased finished leather underwent a comparison with a resin-based finished leather, demonstrating equivalent quality standards as demanded by the market [27].…”

Rheological Investigations of Water-based and Solvent-based Lacquer Varieties and Their Significance in Leather Coating Characteristics

“…It involves three foundation coats: Base Coat, Pigment Coat, and Topcoat. The Base Coat chemically alters surface characteristics, while the Pigment Coat provides uniform color, utilizing fillers and binders for physical enhancement [3]. The Topcoat, composed of polyurethane and cellulose-based lacquers, offers abrasion resistance and fastness because it is reasonably hard and more abrasion-resistant.…”

“…However, due to their toxicity and environmental concerns, these solvent-based PUs are being phased out [1,2,[4][5][6]. Water-based polyurethane (WPU) has emerged as a successful alternative, significantly reducing organic solvent emissions [3,7,8]. To dissolve PU in water, hydrophilic modification is needed, resulting in three WPU types based on hydrophilic components: anionic (carboxylic ion), cationic (ammonium ion), and nonionic (polyethylene glycol) [9].…”