OBTAINING RUBBER COMPOUNDS FOR RUBBER PRODUCTS VIA CHEMICAL DEVULCANISATION OF SCRAP RUBBER
It is known that during the manufacture of mechanical rubber goods (MRG) the rubber compounds undergo an irreversible vulcanisation with the aid of sulfur. Sulfur vulcanisation chemically “sews” the long chains of the molecules of natural rubber into a three-dimensional “grid”. Thus, vulcanised rubber once and for all retains the form it had prior to the vulcanisation process. For molding of new products from worn rubber products it is necessary to return the plastic properties it had – “embroidering” the rubber “grid”.
There are known methods of chemical devulcanisation of scrap rubber. For example, Devulcanisation of rubber by ozone. In this case sulfuric “bridges” are oxidised and rubber is partially devulcanises. However, ozone oxidises the natural rubber a well, worsening its properties again to be vulcanised. Furthermore, the degree of devulcanisation is low, which makes it impossible to obtain rubber compound for molding of new MRG. Ozonisation makes it possible to obtain only rubber powder, for latter addition to regular rubber compounds in a quantity of several percent.
We have developed a process of devulcanisation, which includes impregnation of rubber with special solvent with additives of catalysts and reagents. In this process rubber is destructured, sulfuric “bridges are torn up, sulfur chemically connects, and rubber becomes plastic, suitable for molding. All that remains is to add 2-4% of sulfur, and new rubber products can be made. The quality of the obtained rubber compound is not worse than obtained from the initial materials, i.e. it is completely possible to make new automobile tires of other rubber products from the divlucanised rubber.
The technological solution developed by our company consists of chemical, mechanical and physical stages, preformed on the used rubber which yield a “divulcanisate” – a mix that can be further used, with addition of standard vulcanization compound in low percentage, to produce new rubber products.
Conclusions, based on results of technical and mechanical properties of the tread rubber devulcanisate by the techniques accepted in the rubber industry are as follows:
1. The technical possibility of production of new product formations from the tread rubber devulcanisate has been proved.
2. For achievement of toughness index of technical plate corresponding to GOST 6190 it is necessary to add new tread rubber mixture in the ratio of 4:1 by weight (20% – compound, 80% – divulcanisate).