The Co-Rotating Twin-Screw Extruder, as an alternative to the batch system, is extremely advan-tageous from an engineering perspective. As a dynamic mixer characterized by intermeshing and self-cleaning screws, the extruder is fed in a continuous way with free-flowing material, by means of gravimetric feeders. This assures not only process stability and reproducibility, but also flexibility in the changes to the formulations.

MARIS technology, combined with the mixing capacity of the Co-Rotating Twin-Screw Extruders,has enabled to reach remarkable results also with Total Solid Adhesives. The traditional batch system, for this specific product, is particularly complex. The material adhesiveness, in fact, requires the process to be divided into different stages, each one requiring discontinuous types of machinery.This kind of technology, moreover, demands a significant amount of manual work, which is in turn characterized by the impossibility to grant a perfect reproducibility of the product.

MARIS has exceeded the limits of the batch philosophy, by setting its production logic in a continuous way. The system is in fact based on the use of a sole extruder, completely automatic and self-cleaning, that allows to decrease dramatically the impact of manpower on the system,while granting the capacity to fully and constantly reproduce the material formulations, also thanks to the use of gravimetric Feeders.The capacity of the extruder to adapt itself to the changes in the process parameters enables a full, real-time control on the formulation and, therefore, on the quality of the materials. By means of a complete and synergistic communication with the downstream equipment, it is also possible to easily manage the entire production process.

The experience gained by MARIS with the Hot-Melt and Total Solid applications has been transferred to the Solvent Based Adhesives. This particular category of adhesive is commonly produced in dissolvers, with the use of a noteworthy quantity of solvent. Once that it is spread, the solventis then vaporized, an operation that limits the speed of the entire production phase.The Co-Rotating Twin-Screw Extruders, on the contrary, allow to decrease to a great extent the amount of solvent in the adhesive. This permits to limit the environmental impact of the whole process: a 500 kg/h production is estimated to reduce the emission of solvent in the atmosphere of about 30.000 l/year. The MARIS technology, which is continuous and respects the ATEX norms,helps limiting the plant costs: a smaller percentage of solvent implies quicker evaporation times and, simultaneously, higher production speeds. The volume of solvent saved is related to both theprocess phase and also the storage, thus ensuring a safe production from a security standpoint.

The flexibility of the extruder and its quick response to the variation of the process parameters en-sure a direct and on-line control of the material viscosity. It is therefore possible to use different types of natural rubber, including lower qualities. It is also possible to color the material, with the addition of a further, smaller extruder. This operation, due to the self-cleaningcharacteristic of the two co-rotating screws, is simple and allows to minimize the cleaning times.The MARIS technology for the continuous production of Solvent Based Adhesive is based on two solutions. The first (One Step) is ideal when the primary target isan economical and simple system. The second (Two Steps) enables higher production rates and greater plant flexibility.