Application of formic acid in leather

Application of formic acid in leather

Leather is a denatured animal skin obtained by physical and chemical processing such as hair removal and tanning. Formic acid has been applied in various links such as hair removal, tanning, color fixing and pH adjustment in leather processing. The specific role of formic acid in leather is as follows:

1. Hair removal

Formic acid can soften the fur, and promote the breakdown and removal of protein, which helps in the cleaning and subsequent processing of leather.

2. Tanning

In the tanning process of leather, formic acid can be used as a neutralizing agent to help the tanning agent in the leather to fully play its role, thereby improving the toughness and softness of the leather.

3. Setting and dyeing

During the color setting and dyeing process of leather, formic acid helps the dye to penetrate the leather and enhance the dyeing effect, while protecting the leather from damage caused by dye molecules. The rational use of formic acid can improve the texture of leather and make the surface of leather more smooth and bright.

4. Adjust pH

Formic acid can be used to regulate the pH during leather processing, which reduces pore size and increases the density of the leather, thereby enhancing water resistance and durability. Generally, the pH value of bare skin after desliming softening is 7.5~8.5, in order to make the gray skin suitable for the operating conditions of the softening process, it is necessary to adjust the pH value of bare skin, reduce it to 2.5~3.5, so that it is suitable for chrome tanning. The main method to adjust the pH value is acid leaching, which mainly uses formic acid. Formic acid has small molecules, fast penetration, and has a masking effect on chrome tanning liquid, so that the convergence of small leather grain is fine during tanning. It is often used in combination with sulfuric acid during acid leaching.