March 2014
54
News
Technology
The production of super fine copper
wire has always placed great demands
on lubricant manufacturers to develop
products that satisfy the needs of this
process. The high drawing speeds and
small diameter (and hence low strength)
of the wire mean that it is highly
susceptible to breakages, resulting in
reduced production efficiency.
This can be as a result of inherent poor
lubricity of the fluid or due to a build-up
of deposits on the cones increasing
friction between them and the wire
surface. A successful lubricant must
therefore combine the properties of good
lubrication with excellent cleanliness.
In order to deliver the required
performance, most current super fine
wire lubricants are of the fully synthetic
“chemical solution” type. They avoid the
use of mineral or other oils which are
insoluble in water and require the use of
emulsifiers for them to mix with water as
these have a tendency to form deposits
that would be unacceptable in super
fine wire machines. Instead all of the
components of a chemical solution type
product are fully water soluble meaning
machines run cleaner.
The challenge with chemical solution
type products is to provide adequate
lubrication. Water provides little or no
lubricity in its own right so additives
must be included that can provide this.
Conventional chemical solution products
rely on the use of polymeric materials that
exhibit “inverse solubility” properties.
Inverse solubility is a property exhibited
by certain chemicals that runs counter to
normal intuitive thinking. Everyone knows
that higher temperatures means higher
solubility. Whether it is laundry, washing
dishes or in an industrial cleaning process,
hot water or steam is better at cleaning
because it is better at dissolving than cold
water.
For most chemicals this is indeed true.
However for those that exhibit inverse
solubility the opposite is the case. Higher
temperature means that they become
less soluble until the point they are totally
insoluble in water.
Improvements in lubricants for super fine
copper wire drawing
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Solution at 20°C, left, and Solution at 70°C
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Samples at ambient 20°C
By Chris Nettleship,
technical director,
Metalube Ltd
