Polymer Filtration System - Variable Capacity Continuous Area Filter

Hills has recently commercialized a new type of polymer filtration system.
The new filter was designed specifically to address the problem of variable
polymer residence times often found in bicomponent spinning lines.

With complex bicomponent fiber cross sections, such as segmented, splittable pie
fibers, very small changes in the melt viscosity can have dramatic effects on
the shape and splitability of the fibers.

To solve this problem, it is necessary not only to have excellent temperature
control of the polymer distribution system, but also to maintain uniform
residence times in the filtration systems. This is necessary even though in many
bicomponent spinning lines, the polymer flow rates may be changed frequently.



The new filter is a continuous extended area type of filter, using standard
Memtec candle filter elements. For optimum uniformity and minimum polymer
degradation, each element is totally enclosed in its own housing, with sliding
spool valves to direct the polymer flow to and from the housing. The individual
housings are arranged together in a common structure, with common inlet and
outlet ports. The capacity of the system may be easily varied by the number and
size of the filter elements.

One of the unique features of the filter, is that the polymer cavity in each
housing is slightly tapered such that the polymer flow velocity is varied along
the length of the filter. This gives the polymer approximately constant
residence time as it travels along the length of the filter element.

Another feature of the filter is that individual filter elements may be added
or removed from the polymer streams, in order to allow more constant residence
times as the polymer flows are changed to obtain different bicomponent polymer
ratios. This feature also means that contaminated elements may be individually
changed without interrupting the polymer process or causing a major disruption
in spinning.

When a filter in any one of the assemblies requires cleaning or replacement,
the valves are closed to prevent flow into and out of the clogged assembly. A
small amount of polymer is bled from the selected assembly to effect
depressurization, and the assembly is removed and replaced. The inlet valve is
then opened to allow slow bleeding of polymer into the restored assembly and the
bleed valve is opened to allow air and entrapped polymer to be removed from the
assembly, before placing it back in service. When the bleed valve flow has
stabilized, the outlet valve is opened to allow full flow to be re-established.