Corrotante extruder in the production and mixing in continuous of vulcanizable rubber

In recent years the Maris company has increased its efforts in the search and development preparing facilities completely new and autonomous of other thousand square meters. The new technological laboratory has three extrusion machines dedicated to testing for clients and two extrusion machines dedicated to research and development, as well as all the peripheral equipment for the most varied process type: gravity dispensers, gear pumps, vacuum pumps, court under water, on dry cutting, cutting cords dry, slow mixers and turbomixers, mills, Calenders and new equipment for analysis at the laboratory for the control of materials.

The double corrotante extruder spindle is a machine for continuous dynamic mixing in constant thermal conditions and under control, which can be further subdivided mainly in two parts, reducing group and process area.

The reducer or gearbox serves mainly to transmit the power required to the axis of the spindle to process materials, especially the new gearboxes with a near-perfect couple in typology HT/HS. In addition the 24 Nm/cc have significantly contributed to the development of the continuous process with high viscosity polymers and for the crushing of the rubber.

Processing is the key point for the production of all materials. The normally elements are the spindle of mixing and cylinders, its modularity and standardization is the key part. The elements of the spindle mix or transportation depending on their disposition on the axes allow the operator to countless possibilities of combination and adapt it to a wide range of materials. The cylinders have the dual role of defining the method, so it refers to the points of introduction of the material and to create in the closed mixing chamber very careful control of temperature, through a system of heating external and an internal cooling system with maze of longitudinal channels. Also in this case, analyzing the thermal balance of the energy in the game, have been created specific solutions for the process with the empowerment of the cooling system internal and external.

As regards the supply of materials, the double corrotante screw extruder is able to process all kinds of materials in the form of grain, dust, flakes, fluid and irregular grain, although they must be free Fluidised material and dosificables gravimétricamenteso the rubber which is currently on the market in the form of bread should be necessarily crushed previously. In this case, to achieve a productive simplification and reducing the initial costs of the investment, thus reducing the energy cost of the final material, Maris, in collaboration with an important sector of the crushed society, has conducted tests specific to the granulation of the rubber in a single pass with extremely positive results. The use of gravity dispensers by a feeding percentual of materials that make up the recipe, allows to control electronic and automatically correct dosing of materials with an accuracy of 0.5% for each component, always ensuring a quality of the final product control.

The project of the type of production can go different ways depending on the flow of the production in factory. Currently, Maris may be responsible for the various demands made by customers with a cascade of two extrusion machines process online or through a direct process with a single extruder.

In the Cascade (in two steps) process applies virtually the same work philosophy used currently with discontinuous traditional system composed of a Bumbury carried out by the mass, with a mixer for cylinders (which it frozen and complements it with the introduction and mixture of vulcanizantes chemicals) and a spindle of transport in case require a final profile. In the first extruder was introduced rubber, burdens reinforced with softeners with part of the additives and the mass (which made up the thermally stable part of the recipe); be packaged the material through a system of court head air cooled, is frozen and is sent directly to a second extruder to complete the recipe with the introduction of the chemical elements (cylinder mixer). In this case, the material may be extruded also directly with the required profile.

The direct production process (in one step), initially only gave positive results with rubber that did not require a strong crushing type EPDM, but there was a gap in the limits of application for those hard rubber type SBR or NR requiring a crushing intense to have a good plasticity in the final product. The difficulty which presented this production system was the energy balance just right for a correct grinding of rubber and a good diffusion and distribution of the rest of the components associated with a notable heat dissipation to not create infusos in the mix. The live production system has its advantages for the medium and small production that offers a simplification of the production, reduction in the problems of installation, much more reduced initial investment costs and lower management costssuch as personnel and use of energy low by quantity of product.

By comparing the energy consumed in the production of two mixtures, one of natural rubber and one of synthetic rubber with final viscosity of the product 50 mooney: the system in Cascade (in two steps) has a consumption on the first extruder of 0.27 and second extruder of 0.19with an overall consumption of 0.46 kW/kg for synthetic rubber and a global consumption of 0.43 kW/kg for natural rubber, while that with the direct system (in a step) for the two types of rubber consumption total is 0.26 kW/kg Maris the market awaiting a positive response, that so far and above all cultural reasons, companies in the sector of vulcanizable rubber have been reluctant to the innovations of the ongoing process with the use of corrotantes extrusion machines double spindle.

Maris has been involved in the research and development of a process for the recovery of vulcanizable rubber. The work on Vulcanized rubber is divided in two phases: the first phase provides for the use of a very intense mechanical mixture, while in the second phase is carried out a combined between chemical action and mixing action. The result of this action is to get out of the extruder plastic product with features to be reused in the production process with direct retrieval of the material from the 90 to 100%.