Open plastic mixing mill

An open mill is a short name for an open plastic mixing mill. It is a roller exposed rubber machine used in a rubber factory to prepare plasticated rubber and rubber compounds, or to conduct heat refining, and it is part of the basic equipment in the rubber industry. An open mill mainly relies on two relative rotary rollers to extrude and shear rubber material and cut the macromolecule chains inside rubber through multiple kneading and associated chemical reactions in the process of kneading, which evenly blends all kinds of components inside rubber and finally achieves the purpose of milling. 

An open mill is also used in plastic processing departments and is short for an open plastic mixing mill. In a plastic factory, people generally call it a two-roller machine. An open mill is a kind of mixing plastic equipment applied earlier in a plastic products factory. Its role is to blend and plasticize evenly mixed raw materials and form uniformly mixed and plasticated molten material. When cable materials are produced, an open mill could directly plasticize mixed powder into molten material. 

The mainstays of the rubber industry for over 70 years has been the two-roll (open) mill and the Banbury (internal) mixer. Roll mills were first used for rubber mixing over 120 years ago. The plastics and adhesives industries later adopted these tools. 

After the dispersion milling process is complete—that is, after 24 or more hours of milling—the mill is opened and the plasticizer or plasticizers are poured onto the top of the slip. Most plasticizers are liquids and quite fluid, and therefore this is not a complicated procedure. The plasticizer or plasticizers form a thin film on the surface of the slip in the mill. The weighed quantity of binder, either in powder form or dissolved in one or both of the solvents, is then added to the layer of plasticizer(s). Usually the binder is more soluble in the plasticizer(s) than it is in the solvent(s), so it is good practice to introduce the binder to the plasticizer first. Remember from Chapter 2 that the whole point of the Type I plasticizer is to react with (dissolve) the binder. The plasticizer wets the binder if it is in powder form and aids in the dissolution process. It is also good practice to make sure that the binder, if in powder form, is stirred into the slip mixture before the mill is sealed and returned to the rollers. We have found large clumps of undissolved binder after 12 hours or more of mixing if we didn t follow this simple procedure. 

An open mill has a simple structure, can be made easily, and has easy operation and convenient maintenance and disassembly it is therefore widely used in plastic product enterprises. The disadvantage is a large physical exertion of operators. Under high temperature, the mixing material has to be flipped by hand, and the flip frequency of mixing plastic by hand greatly influences the mixing quality of raw materials. 

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