Note: Descriptions are shown in the official language in which they were submitted.
~5~ 3080~CA
PROCESS FOR CLEANING M~TAL SURFAOES
This invention relates to a process for cleaning metal surfaces
containing poly(arylene sulfide) based deposits.
In the production of poly(arylene sulfide) polymers various
impurities such as polymer gel and inorganic materials are present in the
polymer and can deposit on -the surfaces of the production equipment.
Materials derived from the polymer can also be formed during processing
-the produced polymer, such as in synthetic fiber production. Machine
parts utilized in processing the produced polymer which contain
poly(arylene sulfide) and impurities and which must be cleaned for re-use
include spinnerettes, dies, pack parts, and filters.
Sometimes the poly(arylene sulfide) deposits may be removed
mechanically, bu-t the job is tedious and time consuming due to the
complexity of the equipment. Also, the deposits can be removed by "burn
out" procedures where the metal par-ts containing the deposits are placed
in forced air furnaces and the extreme heat applied removes them. This
"burn out" procedure will no-t work for cleaning all deposits from metal
surfaces such as the specific case of poly(phenylene sulfide) based
deposits. In this case, burn out will result in a metal surface which is
corroded. Therefore, new processes which will readily remove the
deposits without having a corrosive or other deleterious effect on
processing equipment are therefore greatly desirable.
It is therefore an object of this invention to provide a
process for removing deposits on metal surfaces derived from poly(arylene
sulfides).
Other aspec-ts, objects, and the several advantages oE the
present invention will become apparent from this specific-~tlon and the
claims.
In accordance with the presen-t invention, it has been
discovered that deposits on metal surfaces derived from a poly(arylene
sulfide) polymer can be removed by contacting the me-tal surfaces with a-t
least one polyamine compound, represented by the general formula
l3
RlR2N(CH2)X[N(cH2)x]nNRlR2
wherein R1 and R2 can be hydrogen or an alkyl radical having from 1 to 10
carbon atoms; R3 can be hydrogen or an alkyl radical having 1 to 6 carbon
atoms; x can be 1, 2, or 3; and n can be any integer from 1 -to 4, a-t a
temperature and for a time sufficient -to remove said deposits from the
surface of said metal.
~xamples of polyamines suitable for use in the process of -this
invention include:
diethylenetriamine
triethylenetetramine
tetraethylenepentamine
N,N,N',N'~N"-pentamethyldie-thylenetriamine
N,N,N',N',N"-pentapropyldiethylenetriamine
N,N'-dimethyldiethylenetriamine
N,N',N"-triethyldie-thylenetriamine
N,N,N',N',N",N"'-hexamethyltriethylenetetramine
and mixtures thereof.
The term "poly(arylene sulfide) polymer" as used in this
specification is intended to include polymers of the type which are
prepared as described in V.S. Patent 3,354,129 and U.S. Patent 3,919,177.
30 As disclosed in U.S. 3,354,129, these polymers can be prepared by
reacting a polyhalo-substituted cyclic compound containing unsaturation
between ad.jacent rings and an alkali metal sulfide in a polar organic
compound. The resulting polymer contains the cylcic structure of the
polyhalo-substituted compound coupled in repeating units through a sulfur
atom. The polymers which are preferred for use in this invention,
because of their frequen-t occurence in polymer production and processing,
are those p~lyters having the repeating unit -R-S- where R is phenylene,
,
.
3 ~5Z~9
biphenylene, naphthylene, biphenylene ether, or a lower alkyl-substitu-ted
derivative thereof. By "lower alkyl" is meant alkyl groups having one ~o
six carbon atoms such as methyl, propyl, isobu-tyl, n-hexyl, etc. Polymer
can also be made according to a process utilizing a p-dihalobenzene and
an alkali metal sulfide, an organic amide, and an alkali metal
carboxylate as in U.S. Patent 3,919~177.
Suitable polyamines to be used as the cleaning agent should
exhibit some solubility for the particular poly(arylene sulfid~) polymer
being removed. Such polyamine should preferably have a boiling point
greater than about 200C as their use a-t such a temperature has exhibited
enhanced cleaning results.
In carrying out the process of -the presen-t invention, the metal
surfaces to be cleaned are contacted with the polyamine cleaning solution
in any suitable manner and heated at a temperature and for a time
sufficient to effect removal of the deposits for the metal surface.
Generally, the metal surfaces should be contacted wi-th the polyamine
solution a-t a temperature above about 200C and preferably above about
250C for a period of time from about 0.5 hours to about 24 hours.
The cleaned metal surfaces are then removed from the bath and
contacted with any solvent, such as methanol, which will remove any
polyamine remaining on the surface o:E the metal. Then the me-tal surfaces
are contacted with water, dried, and treated with concentrated HNO3 to
remove any remaining contaminants on the metal surface.
In order to provide a clearer understanding of the present
invention, but without limiting the scope -thereof, -the following examples
are presented.
Example I
Poly(phenylene sulfide) (PPS) having a mel-t flow between 200
and 400 as measured at 315C/5Kg (ASTM D-123S, Modified Procedure B) was
extruded at about 300C through a screen-pack comprised of ~ meta:L
screens (1.56 :inches diameter) ~0/80/200/Dynalloy X13L mesh s:ize placed
on top of one another. After several hours extnlsion, the screens
containing poly(phenylene sulfide) deposits were removed and immersed in
200 milliliters of triethylenetetramine and the solution heated at about
260DC for 6 hours. The screens were removed from the hot amine solution
and soaked in methanol at 25C for 1 hour to remove the amine. The
screens were then wa-ter soaked at 25C for 1 hour, air dried and trea-ted
with concentratP HN03 for about 30 Minutes at 25C to remove any
remaining deposits. Weighing the screen pack before and after cleaning
revealed that flbout 85 weight percent of PPS-deposits were removed
indicating good cleaning. Repeating the process at 200C and 280~C gave
about 52 weight percent and 9~ weight percent 9 respectively of
PPS-contaminants removal.
The process was repeated using a glycol and two hydroxy amines
to detexmine their efficiency as a rleaner. None of the liquids te~ted
were satisfactory in removing PPS-deposits rom metals. These results
along with that of a commexcial cleaner are listed in Table I. The
results from the triethylenetetramine cleaning ~re also listed for
comparison.
Sonditions
Run No. Cleaner ~C Hours Results
15 Controls:
1 Triethylene Glycol 250 4 No cleaning
2 Triethanolamine 250 6 No cleaning
3 Ethanolamine 170 6 No cleaning
4 Depoxy 125 4 No cleaning
~ Invention:
Triethylenetetramine 200 6 52~ removal
6 Triethylenetetramine 260 6 85% removal
7 Triethylenetetramine 280 2 99Z removal
aCommercial cleaner from Atomergic Chemetals Corp., Plainville9 NY; 90Z
dimethylsulfoxide, 7~ HN03, 3~ stabilizers and accelerators.
Example II
Poly(phenylene sulfide) (PPS) as described in Example I was
extruded at about 300C through a filter cartridge commonlv used in fiber
spinning operations. This filter cartr;dge identified as Dynalloy X13L
consisted of a 7.5 inches x 1.55 inches O.D. cylinder with an inner and
outer stainless steel support screen (equivalent to about a 40 mesh size)
and an inner fine filter stainless steel mat (46 micron filter rating).
After several hours operation, the filter eartridge was removed, soaked
in triethylenetetramine at 250C for 16 hours and further cleaned by
soaking them in methanol at 25C for 1 hour. The metal surfaces were
then soaked in watex at 25C for 1 hour, air dried! and treated with
concentrated HN03 for about 30 minutes at 25C. By this method, greater
* Trade Mark
s ~ 5~
than ~5 percent of residual PPS-deposits was removed froln the cartridge
Eilter indicating good cleaning. This example illus~rates the use:Eulness
of the instant invention in cleaning other type metal filter screen
systems.
