Open mill

In order to test this concept a series of compounds was prepared in a 5 L Shaw Intermix (rubber internal mixer, Mark IV, Kl) with EPDM (Keltan 720 ex-DSM elastomers an amorphous EPDM containing 4.5 wt% of dicyclopentadiene and having a Mooney viscosity ML(1 +4) 125°C of 64 MU 100 phr), N550 carbon black (50 phr), diisododecyl phthalate (10 phr), stearic acid (2 phr), and l,3-bis(tert-butylperoxy-isopropyl)benzene (Perkadox 14/40 MB ex Akzo Nobel 40% active material 6 or 10 phr). A polar co-agent (15 phr) was admixed to the masterbatch on an open mill and compounds were cured for 20 min at 180°C in a rheometer (MDR2000, Alpha Technologies). The maximum torque difference obtained in the rheometer experiments was used as a measure of... 

The molecular weight of natural rubber (NR) can be altered by mechanical means. Mastication of NR results in a reduction of molecular weight. In the distant past, NR was commonly subjected to mechanical degradation on open mills for extended periods of time to improve processability. 

FIGURE 30.11 Sampling along a compounding line for a filled ethylene-propylene-diene monomer (EPDM) compound curatives addition on open mill. 

A strip of rubber from a previous batch left running round the front roll of an open mill to facilitate loading of the next batch. 

On an open mill, the proportion of the mill load which runs in the space immediately adjacent to the nip between the rolls. 

A heavy type of open mill with deeply corrugated rolls, used for the preliminary breakdown of rubber compound prior to the processes of extrusion and calendering. 

A roll of masticated rubber cut from an open mill, also known as a pig. 

A machine for the incorporation of compounding ingredients into rubber or similar materials. Two rotors revolve in an enclosed chamber (see Open Mill). It is provided with a hopper for feeding the materials and a sliding or drop-door for discharge of the batch. 

The softening of rubber by milling to enable the addition of compounding ingredients to be made. Mastication may be done on an open mill, an internal mixer or in a plasticator. See Cold Mastication and Hot Mastication. 

A machine for masticating rubber, mixing rubber compounds and for warming up rubber compounds prior to calendering, extrusion, etc. See Open Mill. 

That part of a factory which contains the rubber processing machinery known as mills. See Internal Mixer, Mill, Open Mill. 

Any apparatus for making homogeneous mixtures of materials used in rubber manufacture, e.g., blends of dry powders, rubber cements of solutions and rubber compounds themselves. See Internal Mixer, Open Mill. 

A two-roll machine similar to an open mill but of more robust construction, having a higher friction ratio and capable of very close nip adjustment. Refining... 

Plasticising of mixed compound by working on an open mill or in an internal mixer, preparatory to extrusion or calendering. 

An open mill on which the final stages of preparing spreading doughs are carried out. Wetting... 

Open-mill mixing is used mainly for special compounds prepared in small volumes. The advantages of mill mixing are its simplicity, the fact that the operator can control the temperature of the material on the rolls, and an easy cleanup. 

Samples for 180° peel tests were prepared according to standard neoprene recipes (9). Neoprene AC or a graft copolymer prepared from it was mixed on an open mill at room temperature for 20-25 min with the following compounding ingredients in succession ... 

Mixed either in an internal mixer or on an open mill... 

Before introduction of the intensive internal mixers, the mixing was accomplished on open mills — a slow, dirty process requiring skilled operators. An efficient, counter rotating twin shaft internal mixer with elhptical rotating discs was... 

In general, the masticated NR and EPDM were mixed together with other ingredients including compatibilizers and homogenizing agents in an internal mixer or open mills. The rubber compound is cured in an electrically heated press at 160 °C for optimum cure time, which is determined by rheometer. In order to study the... 

Mixing The general methods for incorporating compounding ingredients into dry natural rubber involve the use of either a two roll mill or an internal mixer (e.g. Banbury mixer). Both in the open mill and in the internal mixer, a definite time, temperature, and order of addition of ingredients should be followed for each batch. [59]... 

If the former mechanism can easily be observed in an open mill, the latter is not necessarily apparent because these phenomena occur on a micro-scale. The incorporation involves a decrease in the specific volume of the mix (6). 

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. 

FIGURE 2.73 Section showing the features of a two-roll open mill. 

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