Product category:
Handling and automation equipment
News Release from: Buss AG | Subject: High-performance MX Kneader
Edited by the Manufacturingtalk Editorial
Team on 24 December 2007
Plastics compound kneader takes less
energy
A high-performance kneader for high-grade cable compound production has significantly reduced the melt temperature rise as a function of screw speed.
Shown by Buss, Switzerland, at the K 2007 plastics and rubber trade fair, a high-performance MX Kneader represented a further development of the universal BUSS MKS Kneader The latest MX has a four-flight screw and a redesigned kneading chamber with greater volume and individually optimized processing zones
This article was originally published on Manufacturingtalk on 13 May 2003 at 8.00am (UK)
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Buss said that the mixing effect has been further intensified while at the same time specific energy consumption has been reduced by about 15%.
* Lower production costs - the melt temperature rise as a function of screw speed is significantly less than before, said Buss.
This enables screw speeds up to 750 rev/min.
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Buss told manufacturingtalk.com that its production trials proved that compounding quality with the MX Kneader is higher.
Also, throughput is about 2.5 times more than the earlier MKS Kneader without any size increase.
The MX also takes up less floor space.
These benefits, said Buss, bring considerable savings not only in investment costs, but also in operating costs - thanks to the lower power consumption.
* Primary application: HFFR compounds - with the MX Kneader, BUSS claims technological leadership in temperature and shear sensitive plastics compounding.
The most important field of application for MX Kneaders is in the production of halogen-free flame-retardant (HFFR) cable compounds based on polyethylene/EVA (EVA = ethylene vinyl acetate copolymers).
In case of fire the aluminium hydroxide flame retardant used in these compounds releases water in an endothermic reaction at temperatures as low as approximately 200 deg C.
For this reason the melt temperature during compounding must be maintained below 190 deg C.
For effective flame retardance, filler levels of up to 68 wt% are common - while the cable insulation must still exhibit good values for strength and elasticity.
Development tests and customer production trials have confirmed the expected improvements in throughput and production quality with these challenging HFFR compounds.
For this application the processing section of the MX Kneader has an L/D ratio of 15 (L = screw length, D = screw diameter) and two infeeds.
After compounding, a rugged flanged-on extruder screw builds up the necessary pressure for melt filtration and pelletizing by air/water-cooled die-face cutting.
An automatic screen changer is optionally available for melt filtration.
* Modular design layout enables wide applications - the modular design layout of MX Kneaders allows them to be readily adapted and optimized for compounding many kinds of temperature and shear sensitive plastics.
Typical examples are as follows.
* Semicon compounds (semi-conducting cable compounds) - these normally contain more than 30 wt% of conductive carbon black, whose fine-grained structure must not be destroyed during compounding.
MX Kneaders for this application have an L/D ratio of 15 or 22, with two or three infeeds.
They are fitted with a gear pump for building up discharge pressure, optionally with an automatic screen changer and with an underwater pelletizing system.
* Silane cross-linkable cable compounds - produced on an MX Kneader with 15 D screw length and one infeed; also with gear pump and underwater pelletizing system.
* Masterbatch containing carbon black in very fine particles that must be uniformly dispersed in the polymer melt - MX Kneaders for masterbatch compounding are similar to those for semicon cable compounds, but with higher throughput due to the higher density of the carbon black.
MX Kneaders are available in six sizes with screw diameters from 34 to 140 mm.
* Quiet-running and easily accessible - Buss told manufacturingtalk.com that it had also innovated the MX Kneader drive, The drive consists of a compact water-cooled combination of four asynchronous motors actuating the screw shaft through a planetary gearing.
This quiet-running drive means that the high-performance Buss MX Kneader already complies with the stricter noise limits to be expected in future.
All modules downstream of the MX Kneader, such as the discharge screw or gear pump, melt filter, screen changer and pelletizer, can be shifted at will on two linear axes.
This not only facilitates access to each module for cleaning and maintenance purposes, said Buss, but also enables rapid product changes.
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