Alternative vegetable pretan systems23 November 2009
Silvateam are a leader in the production and sale of vegetable extracts and speciality chemicals for a variety of industries including leather. They have devised two alternative vegetable tanned systems using pretanning agents on wet-white
Metal free tanning systems whether used alone or in combination are ideal for softer articles such as garment or automotive leather or firmer items such as belting, vacchetta or sole leather.
Silvateam were established in 1854 and built their first natural tannins factory in Piedmont, Italy, quickly acquiring other facilities to increase the production of Chestnut extract.
The extract industry was also developing in other regions where suitable raw materials were available, including Argentina. In 1927 the production of Quebracho extract started in the La Escondida factory, in the northern Chaco region of Argentina.
With an annual turnover of more 100 million euro in 2008, Silvateam have grown considerably during the last few years. Today the company is based in Italy, South America and China with six manufacturing facilities, warehouses and approximately 800 employees.
Their extended sales and distribution network allows Silvateam to serve more than 10,000 customers in 60 countries worldwide.
Tannins are astringent, bitter plant polyphenols with many effects on biological systems: potential metal ion chelators, protein precipitating agents and they act as a defence mechanism in plants against pathogens, herbivores and hostile environmental conditions. Furthermore several studies have shown that tannins have positive effects on human health as antioxidants and free radical scavengers.
An alternative way to produce vegetable tanned leathers is to start from a pretanned leather base (wet white) in order to save on the amount of tannins used in the main tannage. In the Silvateam R&D laboratories we have studied the behaviour of two new tanning agents, Ledosol XT and Blancotan MSR, used either as a metal free pretannage alone or in combination with each other. The aim was to understand the link between the tanning agents employed and the kind of article obtained.
Product characteristics – Ledosol XT
Ledosol XT is a liquid pretanning agent that has very good dispersion and penetration properties into the leather fibres. Only 4–6% is required to produce very good leather that has a light, warm colour and good lightfastness. These characteristics are especially useful when producing soft and light weight articles such as garment, car seat, light shoe upper and leathergoods (such as wallets and handbags).
Blancotan MSR is a powder that can be used as a pretanning and/or tanning agent and has a high tanning power. It also has good penetration and dispersion that make it suitable for the production of wet white leathers.
The final leathers have a number of positive properties including an elastic grain, a soft feel and a light colour. A pretannage with Blancotan MSR is recommended for leathergoods or any articles treated with vegetable tannins where the typical vegetable tanned characteristics are required such as firmness, roundness and tightness, which are required for items such as for vacchetta, belting and sole leather.
Another special feature of Blancotan MSR is that it is an environmentally friendly pretannage. Using this product it is possible to pretan leathers using salt free floats to pickle the leather thanks to its natural salt content.
Blancotan MSR and Ledosol XT show good pretannage characteristics and can be used with any standard chrome tannery machinery and equipment. Blancotan MSR is suitable for heavy and firmer articles while Ledosol XT is more suited for softer and flexible leather types. Additionally, Blancotan MSR and Ledosol XT can be combined in different percentages to obtain finished leather products with a range of desired characteristics. n