New hydrophobing agents from Z&S

The demand for hydrophobic leathers has substantially risen in the last few years, since the chemical industry manufactures products that despite simple application lead to the desired results. According to Zschimmer and Schwarz, the advantages offered by leathers treated with the modern hydrophobing agents are obvious. These include: An excellent water-repellence is obtained even under dynamic stress. 100 000 flexes in the Maeser test are possible; Water absorption is low, so the leathers do not become considerably heavier during use; The treated leather is made hydrophobic evenly throughout the entire leather cross-section, so that the water-repellent effect is maintained even when the surface is damaged; Even after a partial humidification and subsequent drying the leathers remain soft and supple; The leathers are easy to maintain as they can be cleaned with water; Neither the natural porosity of the leather, nor its water vapour permeability are affected; The leather is hardwearing and looks new for longer, despite constant use. In order to produce this kind of leather, there are some important conditions which must be considered. The leather has to be treated in such a way as to make it waterproof. Water-in-oil emulsifiers are applied to ensure that the leather fibres up to the fibril are coated with a monomolecular film. After that the hydrophilic functional groups (that are necessary in order to be able to emulsify the product in water) have to be inactivated. This is usually achieved by fixation with metal salts. In some cases the existing chromium in the leather is sufficient for fixation so that only acidifying with formic acid is required. Zschimmer & Schwarz's hydrophobing agents composed on this basis include: Dolagen WP, a phosphoric acid ester for garment leathers; Dolagen S, a water emulsifiable polysiloxane; Dolagen HFN, a synthetic copolymer for soft shoe upper leather; and Dolagen PM, a special copolymer which does not require metal salt fixation. Dolagen HSL is the newest development from the research laboratory of Zschimmer & Schwarz. This product is based on a polymeric matrix which contains long-chain phosphate groups, which can be used especially for tight and firm leathers. More than 100,000 maeser flexes are possible. Further advantages include excellent light and heat fastness as well as an anti-wrinkle effect and very good water vapour permeability.