Leather Auxiliaries for leather
Product Details
Leather auxiliaries (also called leather chemicals) are indispensable "magicians" in the leather industry. They permeate the entire complex journey from raw hide to finished leather product, determining the final quality, feel, and function of the leather at each step.
Let's follow the leather's "transformation" process to see which key stages these auxiliaries work their magic at:
Application by Production Process
1.Preparation Stage (Pre-treatment): Laying the Foundation for Tanning
This stage transforms raw hides (raw hides) into storable, tanned "naked hides," primarily removing impurities and restoring the hide to its natural state.
Immersion Auxiliaries: Contain surfactants and preservatives. They help dry, salted raw hides quickly and evenly absorb water to soften them, restoring them to a fresh hide state, while preventing bacterial growth that could lead to rotting.
Degreasing Agents: The main component is surfactant. For hides with high fat content (such as pigskin and sheepskin), it efficiently emulsifies and removes the oils within the hide, ensuring smooth penetration of subsequent chemical materials.
Lime/Depilatory Agents: Typically a combination of sulfides and lime. Responsible for removing hair and epidermis, and appropriately swelling and loosening the leather fibers to prepare for subsequent cutting and separating of collagen fibers.
2.Tanning Stage: The Transformation from "Hide" to "Leather"
This is the most crucial step, using tanning agents to transform perishable "hide" into stable and durable "leather."
Tanning Agents: These are the core auxiliary agents in leather production and can be divided into several categories:
Mineral Tanning Agents: The most commonly used is chrome tanning agent, which imparts excellent softness, resistance to damp heat, and fullness to leather.
Synthetic/Vegetable Tanning Agents: Such as phenolic synthetic tanning agents or vegetable tannins. They can be used alone (to produce heavy leather), but are more often used in combination with chrome tanning agents as retanning agents to adjust the fullness, grain density, and hand feel of the leather.
New Environmentally Friendly Tanning Agents: To address environmental challenges, chrome-free/formaldehyde-free tanning agents have become a research hotspot. For example, tanning agents developed using hyperbranched polymers not only effectively tan (making the leather shrinkage temperature >75℃) but also possess good biodegradability.
3.Wet Finishing Stage: Imparting Softness and Filling
The tanned leather is still relatively dry. This stage mainly involves "moisturizing" and "shaping" the leather.
Fattening Agents: These are among the most widely used leather auxiliaries, used to lubricate leather fibers, giving the leather a soft, full feel and a certain degree of water resistance and breathability. They come from various sources:
Natural Oil Processings: Such as sulfated castor oil (Taikoo oil), succulent fish oil, etc.
Synthetic Fatliquoring Agents: More stable, such as phosphate esters and bound fatliquoring agents.
Functional Fatliquoring Agents: Such as silicone-modified fatliquoring agents, which can give leather a silky smooth feel and excellent resistance to yellowing.
Retanning agents/fillers: Used before and after fatliquoring, such as acrylic resin retanning agents, to fill the fiber gaps in soft areas of the leather, making the thickness and feel of the entire piece of leather more uniform, while also enhancing the leather's abrasion resistance and strength.
4.Dry Finishing Stage (Coating): Creating a Perfect "Face"
This stage involves "dressing up" and "coating" the dried leather surface to cover imperfections and give it the final color, shine, and feel.
Finishing aids: This is a complex formulation system that works together to coat the leather:
Film-forming agents: Such as water-based polyurethane and acrylic resin emulsions, these are the main components of the coating, forming a thin film that adheres to the leather surface.
Coloring agents: These are dyes or pigment pastes responsible for giving the leather the desired color.
Hand feel agents: Such as amino polyether modified silicone oil emulsions, these can adjust the smoothness, waxiness, or oiliness of the leather surface, improving the tactile quality.
Leveling agents: These help the coating spread evenly during the drying process, preventing brush marks or orange peel texture. Thickener: Adjusts the viscosity of the coating slurry to suit different processing methods such as spraying and roller coating.
Defoamer: Eliminates air bubbles generated during the mixing and application of the coating slurry, preventing defects such as pinholes in the coating.
Crosslinking Agent/Fixer: Improves the coating's resistance to wet rubbing, dry rubbing, and solvents, resulting in stronger color and coating adhesion.
Key Application Points and Trends
Complex Systems, Critical Compatibility: Similar to papermaking, leather processing involves numerous wet operations. The order of addition and compatibility of different leather auxiliaries (cationic and anionic) are crucial; otherwise, precipitation or failure may occur.
Environmental Protection and Functionalization: The industry is accelerating its development in two directions
Greening: Research and promotion of chromium-free/formaldehyde-free tanning agents, fluorine-free waterproofing agents, and biodegradable fatliquoring agents.
High Performance: Development of leather auxiliaries for high-end applications, such as fatliquoring agents and finishing agents with low fogging values and high light fastness that meet stringent standards for automotive interiors.