5~3
SEPARATION PROCESS
TECHNICAL FIELD
The present invention relates to modified polyelectrolytes which are
useful as flocculents in separation processes, to processes for preparing the
modified polyelectrolytes, flocculent compositions incorporating the modifiecl
polyelectrolytes and to separation methods employing the modified
polyelectrolytes and modlfied polyelectrolyte compositions of the invention.
The modified polyelectrolytes of the invention perform better than the
prior art polyelectrolytes in that they are capable of achieving the same
level of flocculation at lower concentrations and are capable of retaining a
higher percentage of super fines.
BACKGROUND ART
Introduction of synthetic water-soluble polymers to the mining industry
in 1951 represented a major development in solid-liquid separation by chemical
reagents. They were the first of a wide range of flocculents tailored to meet
many needs such as clarification of water (municipal and industrial),
treatment of municipal sewerage and industrial waste (food processing, oil
refining, metal finishing, pulp and paper mills etc.), mineral processing
(benefication, recycle-water clarification, effluent treatment), and
manufacturing processes (paper production, sugar refining, phosphoric acid
production etc.).
Although there are a large nurnber of commercially available synthetic
flocculents the number of significantly different types of chemical structures
is relatively limited. In the market place selection of a flocculant depends
on optimizing the cost-to-perforrnance ratio, that is, achieving clesired
performance at minimal cost. Although a systems point of view predominates
(including flocculant availability, reproducibility, handling, storage~
tolerance to fluctuatiorls in treatment-plant loading while meeting outpu-t
specifications, equipment-in-place and necessary modification etc), the
delivered cost per unit weight of individual flocculants enter as one factor.
Consequently, a relatively few monomers suitable for incorporation into
water-soluble polymers and produced on a sufficiently large scale to have low
cost, are the major building blocks of commercially important synthetic
polymeric flocculants.
Practical synthetic organic flocculants are water soluble polymeric
substances with weight average molecular weights ranging from about 1000 to
greater than 5 million (reported values as high as 20 million).
Polyelectrolytes used as flocculants include polymers and copolymers
made from a number of monomers including maleic anhydride, maleic acid,
3720M
--2--
acryl~c ac~d, acrylam~de, acrylonltrile, methacrylic acid, vlnyl sulfonic
acld, p-styrene sulfonlc acid, styrene, vinyl methyl eth~r, metaphosphoric
acid, vinylamine, ethyleneimine, vinyl pyr~dine and 4-vinyl-N-
dodecylpyridinium chloride.
DISCLOSURE OF THE INVENTION
In a first embod~ment of the invention th2re is provided a modlfied
polyelectrolyte characterized in that a polyelectrolyte is reacted with a
copolymer of at least two ethylenically unsaturated monomers, at least one of
which contains anhydride groups.
In a second embodiment of the invention there is provided a process for
manufacturing a modified polyelectrolyte, which process comprises reacting a
polyelectrolyte with a copolymer of at least 2 ethylenically unsaturated
monomers, at least one of which contains acid anhydride groups. The reaction
can be initiated by heat and/or by an inorganic accelerator such
as a metallic base. A suitable accelerator is potassium carbonate.
The types of known polyelectrolytes suitable for use in this invention
are extremely numerous and diversified. No unsuitable commercially available
or laboratory synthesized polyelectrolyte has been found. Common trade names
defining such polyelectrolytes include: SANYOFLOC; ALFLOC; SUPERFLOC;
MACROFLOC; MAGNAFLOC; MAXFLOC and ZETAG.
Other materials designed for the same or similar purposes to those
described above may also be used.
Generally, the polyelectrolytes which can be modified according to the
invention have molecular weights in the range 2xlO~ to lx108, especially
lxlO5 to 7xl0h daltons. The preferred copolymers with which the
polyelectrolytes are reacted have molecular weights in the range lxlO~ to
lx106 daltons.
It is particularly preferrerl that a known polyelectrolyte flocculant is
reacted with a copolymer o~ methyl vinyl ether and maleic anhydride.
A third embodilllent of the invention provides a further modified
polyelectrolyte characterized in that the modified polymer according to the
first embodiment of the invention is further modified by reaction with vinyl
pyrrolidone or polyvinyl pyrrolidone followed by further reaction with the
copolymer.
A fourth embodiment of the invention provides a process for
manufacturing a further modified polyelectrolyte which process comprises
terminating the process according to the second embodiment of the invention
by reducing the temperature, dispersing the reaction mixture with vinyl
pyrrollidone or polyvinyl pyrrolidone and allowing the reaction to proceed.
~."~0~ S ~3
The further reackion can also be ini-tiated by heat and/or by
an inorganic accele~ator.
A fifth errbodiment of the invention provides a flocculating composition
cornprising a modified polyelectrolyte or a fuIther modified polyelectrolyte
according to the invention in association w~th the usual carriers and dlluents
employed in conventional flocculating compositions.
A sixth embodiment of the invention provides a method of flocculation
which method comprises adding to a material to be flocculated a modified
polyelectrolyte, a further modified electrolyte and/or a flocculating
composition according to the invention.
BEST MODES OF CARRYING OUT THE INVENTION
Polymer solids at an amount of between O and 200%, preferably 10/ (on
the basis of polyelectrolyte solids) may effectively be employed in this
in~ention.
Generally, the reaction is carried out by simple mixing or
homogenization of the polyelectrolyte and copolymer. Reaction times and
reaction temperatures will depend on the nature of the polyelectrolyte and the
copolymer but generally the reaction can be carried out at temperature of
between 0 and 120C for a time of between 5 minutes to 4 hours. It is
preferred that the polyelectrolyte and copolymer be selected such that the
reaction can be carried out at a temperature of bet~leen 40~ and 80C ior a
time of up to 50 minutes. Preferably, the reaction is carried out in solution.
In order to further modify the polyelectrolyte, the reaction is stopped,
preferably by reducing the temperature to below 30C, vir1yl pyrrolidorle or
polyvinyl pyrrolidorle is added, l:he mixture is agil:ated or stirred to disperse
the vinyl pyrro1i(lo~le or polyvinyl pyrrolidone and the mixtul-e is reheated torestart the reaction. I:E there is an excess of copolymer, the vinyl
pyrrolidone or polyvinyl pyrrolidone reacts ~ith the anhydride
moiety of either reacted or unreacted copolymer resulting in a
mixture of further modified polyelectrolyte and mofified copo-
lymer.
It is preferred that the r~tio of vinyl pyrrolidone or polyvinyl
pyrrolidone to copolymer is in the range 1:1 to 1:10 by weight, more
preferably l:S by weight.
* by weight
L9
- 3a -
The following examples illustrate preferred embodiments of the
invention and should not be construed as limiting on the scope thereof.
EXAMPLE 1
11 polyelectrolytes were reacted with various methyl vinyl ether/maleic
anhydride copolymers. The types of base polymers are set out in Table 1.
Table 1
Example Tvpe ~ Approx MW
(daltons)
O Polyacrylamide 5x106
1 Copolymer of Sodium Acrylate and Acrylamide 6X106
2 " 6X106
6xlo6
4 ~1 6xlO6
.. . . .. ..
~.,Q~ ''3
., 5%,o6
6 " 1x106
7 Terpolymer of Acrylamide, Sodium Acrylate and
Maleic Anhydride lx105
8 Terpolymer of Acrylamide, Sodium Acrylate and
Vinyl Pyridine lx106
9 Copolymer of Sodium Acrylate and Acylamide 5X106
10 Polysodium Acrylate lx106
NOTE: It can be seen that samples O to 10 range from nonionic to 100% anionic.
The polymers ln Table 1 were reacted with poly methyl vinyl
ether/maleic anhydride copolymers of the following molecular weights:
20,000; 67,000 and 80,000.
All reactions were carried out by dispersing the poly methyl vinyl
ether/maleic anhydride copolymers in the finished base polymer. This blend
was then placed in a water bath at 80C and the reaction occurred within 40
minutes. The end point of the reaction could be determined as a visible
physical change in the base polymer.
lhe amounts of poly(methyl vinyl ether/maleic anhydride) were varied
between O to 100% of the solids of base polyelectrolytes.
The results obtained demonstrated that maximum efficiency ~as
determined by maximum performance for lowest amount of material) was at 10%
polymer solids (based on polyelectrolyte solids) wlth molecular weight of
poly(methyl vinyl ether/maleic anhydride) at 67,000 daltons.
Example 2 is based on the above percentage and molecular welyht. The
base polymer number refers to Table 1.
~XAMPLE 2
The polymers prepared in Example 1 were evaluated for efficiency by
comparison with the polyelectrolytes from which they were derived. In all
cases the performance of the new materials was superior to that of -the
polyelectrolytes from which they were derived. Comparisons conducted at
mine sites were advantageously done by selecting a polyelectrolyte with
correct charge density for the materials being separated and comparing
these with modified polyelectrolytes comprising the same base
polyelectrolyte and possessing the same or similar charge density.
Whilst these examples are based on coal flocculation, the same and/or
similar benefits can be attained wherever polyelectrolyte technology is ln
use.
The following results ~Jere obtained in laboratory scale testing on
site at the following coal washeries:
3720M
~ 3a)~S 4 ~3
1. Mount Thorley [R.~. M~ller]
2. ~est Cllff [Kembla Coal & Coke]
3. Hunter Valley No.l [Coal & Allied]
1. Mount Thorley
A. Base Polymer No.6*
Settling Velocity 8.2m/h
Clarity Good
B. New Polymer No.6R*
Settling Velocity 18.0 m/h
Clarity Good
2. ~est Cliff
A. Base Polymer No.2~ No.3*
Settling Velocity 1.0 m/h 0.8 m/hz
Clarity Good Good
6. ~ew Polymer No.2R~ No.3R*
Settling Velocity 1.25 m/h 1.4 m/h
Clarity Very Good Very Good
3. Hunter Valley No.l
A. Base Polymer No.4 No.5 No.6
Settling Velocity 4.3 m/h 8.3 m/h 6.1 m/h
Clarity Very Poor Very Poor Very Poor
B. Base Polymer No.4R No.SR~ No.6R
Settling Velocity 9.9 m/h 20 m/h 20 m/h
Clarity <Poor <Poor <Poor
~ Indicates tne correct charge de1lsi~y on the base polymer
m/tl Metres/11oul^
R ~here a second reaction has been performed on the base polymer.
EXAMPLE 3
A Latex polymer of the following characteristics was prepared.
Organic solids 32.0X pH(1%) 6.0
Ratio Acrylamide:Dimethylaminoethyl
Methacrylate 60:40 nominal mw 2X106
This polymer was cooled to below 30C then further reacted with l.5%
by weight poly(methyl vinyl ether/maleic anhydride) with a mw 80,000
(daltons). The reaction was carrled out by dispersing the powder through the
latex and placing into a water bath at 50C for 50 minutes. On cooling the
flocculent latex was packaged.
V,~ r11~
- G - .
The following results were obtained from testing work on a
undigested sewerage sludge obtained from a sewerage -treatment pla~t.
A. Base Polymer dose 240 ppm
Settling Velocity 2.6 m/h
Shear resistance pass
8. New Polymer dose 240 ppm
Settling Velocity 4.7 m/h
Shear resistance pass
m/h Metres/hour
EXAMPLE 4
A solution polymer of the following characteristics ~as cooked.
Organic polymer solids 6/~ pH(neat) 8.0
Ratio Acrylamide:Acrylic Acid 60:100 nominal mw 6X106
This polymer was reacted with 0.5% polymer (methyl vinyl ether/maleic
anhydride) with a mw of 67 000 daltons(ex GAF). The reaction was carried out
by dispersing the powder through the solution and placing into a water bath at
60C for 4 hours. The resultant mixture was cooled to below 30C and 1.0% of
polyvinyl pyrollidone was dispersed into the mixture. The mixture was
replaced into the water bath for 2 hours. On cooling the flocculent solution
was packaged.
EXAMPLE 5
A latex polymer oF the following characteristics was prepared.
Organic solids 28.5% pll(~VL) 3.0
Ratio Acrylamide:Acrylic Acid 3~:23 nolllinal mw l2xloG
This polyrller was cooled to below 30C then flJrthet- reacted with 2.5%
by weight of poly(methyl vinyl ethQr/maleic anhydride) mw 67 000 (daltons)
dispersed in twice its weight of in aromatic solvent. This mixture was cooled
to below 30C and 0.5% of polyvinyl pyrrolidone was dispersed in the mixture.
The mixture was replaced into the water bath for 30 min. On cooling the
flocculent latex was packaged.
EXAMPLE 6
A solution polymer of the following characteristics was prepared.
Organic polymer solids 6X pH(neat) 8.0
Ratio of Acrylamide:Acrylic Acid 7:1 nominal mw 5X106
~;J~
-- 7 --
Th7s polymer was reacted wlth 0.5% poly(methyl v~nyl ether/male~c
anhydr~de~ with a mw 80 000 daltons. ~he reactlon was carr~ed out by
d7spers1ng the powder through the solution and plac~ng lnto a water bath at
60C for 4 hours. The resultant mixture was cooled to below 30C and 0.1% of
polyvinyl pyrrolidone was dispersed in the mixture. The mixture ~Jas replaced
into the water bath for 2 hours. On cooling the flocculent solution was
packaged.
EXAMPLE 7
A solution polymer of the following characteristics was prepared.
Organic solids 6% pH~neat) 8.0
Ratio of Acrylamide:Acrylic Acid 50:50
This base polymer was reacted with 0.5% w/w poly~methyl vinyl ether/
maleic anhydride) with a mw of 67 000 daltons. The reaction was carried out
by dispersing the powder throuyh the solution and placing into a sealed
container in a water bath for 4 hours at 60C. The resultant mixture was
cooled to below 30C and 0.1% of polyvinyl pyrrolidone was dispersed in the
mixture. The mixture was replaced into the water bath for 2 hours. On
cooling the flocculent solution was packaged.
EXA~PLE 8
A solution polymer of the following characteristics was prepared.
Organic solids (of acrylic acid) 6~1~ pHtneat) 8.0
This base polymer was reacted with 0.5% poly(methyl vinyl ether/maleic
anhydride) with a mw of 67 000 daltons. The reaction was carried out by
dispersing the powder through the solution and placiny i-t into a sealed
conr~iner in a water bath for ~ hours at 60C. Ttle resultant mixture WdS
cooled to below 30C and 0.1% of polyvinyl pyrrolidone was dispersed in the
mixture. The mixture was replaced into the water bath for 2 houls. On
cooling the flocculent solution was packaged.
The following results were obtained i.n labora-tory scale
testing on site at the following coal washeries:
I. Mount Thorley [R.W. Miller]
Hunter Valley CPP CCoal & Allled]
II. Ravensworth Colliery [Elcom]
III. West Cliff CKembla Coal & CokeJ
IV. Hunter Valley CPP [Coal & Allied]
I. Mount Thorley
A. Base Polymer
Settling Velocity 8.2m/h
Clarity Good
B. New Polymer
Settling Velocity 29m/h
Clarity Very Good
I. Hunter Valley CPP
; A. Base Polymer
Settling Velocity 6.lm/h
Clarity Very Poor
B. New Polymer
Settling Velocity 18.4m/h
Clarity poor
II. Ravensworth
A. Base Polymer
Dose 5ppm
Settling Velocity 4.0m/h
Clarity 65% at 400nm
B. New Polymer
Dose 5pp~l1
Settling Velocity 12.8m/h
Clarity >90% at 400nm
III . West Cli~f
A. Base Polymer
Settling Velocity 0.8m/h
Clarity Good
B New Polymer
Settling Velocity 2.9m/h
Clarity Very Good
IV. Hunter Valley CPP
A. Base Polymer
Settling Velocity 8.3m/h
fb,~ 3
. g
Clarity Very Poc,r
B. New Polymer
Settllng Veloclty 27.1m/h
Clarity Good m/h Metres/hour
It can be seen from the test data that not only are these compounds a
more cost efficient base (on the reaction being done on the compound of ideal
charge density in order to coincide with the material being separated), but
they also allow for a far greater latitude in charge density wllilst
maintaining performance. This is of particular importance in the mining
industry where frequent (and sometimes dramatic) changes in charge density
requirementS are experienced throughout the mining process [e.g. change in
orebody, change within a coal seam, or changes from coal seam to coal seam.
changes in climatic conditions affecting the treatment of sewerage. ~lany
other examples can be quoted]
INDUSTRIAL APPLICATION
The present invention provides modified polyelectrolytes which are
useful as flocculents and find use in separation processes from fields as
diverse as ~later treatment, oil refining, metal finishing, food processing,
paper milling, mineral processing and rnanufacturil-~g processes.
