Every new rubber compound and every new mixture
component not only entails new properties for the end
product, but also significantly alters the process be-
haviour of the material during mixing and further pro-
cessing. Silica compounds have been tried and trusted
in the manufacture of car tyres for a number of years,
because many relevant factors, such as noise emissions,
rolling resistance and braking distance can be positively
influenced by their use. For the production of the basic
rubber material, however, the use of silica additives cre-
ates completely new challenges in relation to the mixing
process and how the finished rubber compound is
handled, especially when it comes to master batches.
Complex chemical reactions between the individual
components and additives take place during the mixing
process. When silicic acid is used, this is grafted onto
the filler surface during mixing by means of a compound
such as silane and later (in the heating press) chemically
bonded to the polymer. The properties of the finished
tyre can be improved considerably as a result of this
process. However, silica compounds prove to be highly
adhesive on the mixing line. This means that the rubber
compound ‘sticks’ more firmly to the inside of the mixing
chamber, the discharge screws and the rollers on the
roller die, which turn the master batch into a six- to
eight-millimetre-thick coat that clings to the rolling mills
and twin-screw discharge extruders.
The HF MIXING GROUP has come up with a solution to
this problem in the form of ASMACool. Its combination
of roller design and surface, and controlled roller cool-
ing is new and totally unique. ASMACool stands for
The HF engineers discovered that merely controlling the
temperature of the discharge rollers can only counteract
the sticking effect to a limited extent, so the classic di-
lemma of wishing to have the cake and eat it had to be
solved in a different way. Accordingly, in a series of tests
carried out at HF, the interaction between the rubber
mass and the roller surface was examined in-depth. The
developers discovered that the gases released, especially
by certain silica compounds, have a highly corrosive
effect on the roller surface. As a result, the surface be-
comes rougher, which in turn helps the medium – in this
case the compound – to stick to it.
Their answer was to use a special process to produce
high-strength, corrosion-resistant hard plating for the
rollers, which suppresses the aforementioned phenom‑
e‑non to the greatest possible extent. The armour plating
on an ASMACool roller is so hard that not even a foreign
body such as a hammer or spanner can damage it. A
further advantage is the fact that the rollers can be repaired
on-site using build-up welding. This special anti-stick
coating is currently only offered by HF. Virtually all the
commonly used rolling mills and roller dies supplied by the
HF MIXING GROUP can now be fitted with ASMACool
rollers. It is a unique selling point which offers customers
in the tyre and rubber goods industry significantly higher
discharge yields, while also improving the effectiveness of
the mixing lines, minimising maintenance work and un-
planned downtimes caused by jammed rollers and gener-
ally increasing process safety. This development was not
only conceived with a focus on silica compounds, but
primarily against the backdrop of the increasing number
of new raw materials and chemical components that will
define the future of tyre and rubber production.
Cool yet tough
ASMACool rollers –
the non-stick solution from the HF MIXING GROUP.
Rolling with ASMACool.
This reliably prevents the master batch from sticking to the roller.
Rolling without ASMACool.
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