Exploitable results Trials on mechanical dehairing machine The partners performed the trials on semi-industrial scale on the mechanical dehairing machine CM using pre-treated hides as obtained following the procedures described in paragraph 1 (Chemical preparation of the hides for mechanical dehairing using traditional chemical agents, amines/mercaptanes, reducing chemical agents, enzyme/other agents). The trials confirmed the possibility to use in the tanning cycle the mechanical dehairing phase having in this way environmental and process advantages maintaining the very good quality of the final products. Mechanical dehairing machine design and realisation The dehairing machine project developing has been carried out in order to produce a machine with right properties for working in tanning industry. CM thought to a machine that, keeping the structure and dimensions of a traditional fleshing machine, allow to contemporary carry out two of the primary operations of the tanning process. the fleshing and the dehairing. The DEHAIR-M was projected in two different versions depending from the available width: 2700 mm and 3200 mm, taking in consideration the specific needs of the fleshing and dehairing phases of the cow hides (even it is possible to perform modifications to adapt it to other kind of hides). The machine was realized in a monolithic structure of steel, solid, strong and surely resistant to the high degree of corrosion of the tanning wet phases. The machine is characterized by simply of the construction, good quality of the materials, reliability, maintenance facility, very high velocity of working. Chemical stabilization of the hides using modified aldehydes, melammine and other cross-linking agents, other chemicals and neutral salts Bovine hides are stabilized with different offers of neutral salts, such as anhydrous sodium sulphate with sulphuric acid to decrease the pH. The best result was obtained applying 8% of anhydrous sodium sulphate at pH 8.1/8.2. Also, sheepskins are stabilized with superneutral sodium silicate and low offer of chrome salt. In these trials, the best result was obtained applying 1.5% of chrome salt such as pre-treatment of skins, working at final pH of 3.7. Besides bovine hides are stabilized with modified aldehydes. The best results are obtained by increasing the quantity of glutardialdehyde (0,5%) and contemporary the quantity of a fat dispersing agent (0,5%). The stabilization by cross-linking agents is successful. The trials performed during the research have highlighted some aspects among witch we consider worth mentioning "a larger tearing resistance of the hides, 10-15% increase of the hides thickness, shaving from the mechanical operation free from CrIII and/or other heavy metals and therefore recyclable as a raw material in the fertiliser industry" The stabilization tanning trials of the above mentioned stabilized hides The bovine hides stabilized with neutral salts are tannaged by a normal offer of chrome salt at different pH. The best global results of physical tests are obtained in the split treated at pH 5.0.The sheepskins stabilized with superneutral sodium silicate are tannaged/retannaged with synthetic phenolic agents and mimosa extract with the aim to obtain shoe upper leather. The bovine hides stabilized with modified aldehydes and fat dispersing agents are chromium and vegetable tanned with good results. The stabilization by cross-linking agents influences the following mineral tanning, because, the chromium can be easier bound by the functional groups introduced with the resin. Consequently, it is possible to observe a drastic reduction of the chromium (residue) in the exhausted baths (95% of reduction instead of the normal 75%). Chemical preparation of the hides for mechanical dehairing using traditional chemical agents, amines/mercaptanes, reducing chemical agents, enzyme/other agents Several chemical agents have been studied to perform the hair loosening in order to prepare the hides for the mechanical dehairing. Sodium sulphide and sodium sulphydrate are the reducing agents more efficiency. Working with small quantities of NaHS (0.3-0.4%) and NaOH (0.7-0.9%), in relatively short times, good hair loosening results were obtained. However, the resulting hides are not totally clean. Besides, good results for the wet-salted as well as the hair dried hides were obtained with enzymatic soaking, immunization with lime, mixture of amine and mercaptane together with a small quantity of sodium sulphide. The use of protheolytic enzymes such as soaking auxiliary or such as principal agent of unhairing is a good system to perform an efficient hair loosening. The use of enzymes needs an accurate control of the working parameters to avoid the nubuck effect on grain surface. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
