Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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6530-382
It is well known that polyacrylamides may be rendered
cationic by subjecting them to the Mannich reaction. This
consists of reacting a substantial quantity of the acrylamide
groups with formaldehyde and a lower dialkyl amine. The thus
reacted polymers may be rendered more basic by quaternizing them
with either a lower alkyl halide or a lower dialkyl sulEate.
Polymers of this type find use in many areas of indus-trial water
treatment for coagulating or flocculating suspended solids. A
particular useful area that utilizes quaternary ammonimum salt
derivatives of these cationic polymers is the coagulation of
suspended solids from industrial wastes and sewage. Polymers of
the above type and their method of preparation are described in
U.S. Patents 3,897,333 and 4,010,131. It should be noted that
these polymers are prepared utilizing either a conventional
polymerization technique or they are prepared by using a water-
in-oil emulsion polymerization technique which is described in
detail in U.S. 4,010,13].
In its broadest aspect this invention provides a method
of coagulating suspended solids from industrial waste water which
comprises treating said water with a few ppm, e.g. 5-200 ppm, of
a water-soluble, crosslinked polyacrylamide which has been
subjected to the Mannich reaction with formaldehyde, a lower
alkyl secondary amine, and subsequently quaternized with a lower
alkyl halide or a lower dialkyl sulfate, said crosslinked
quaternized polymer being further characterized in that the
starting uncrosslinked acrylamide polymer has a molecular weight
CASE 84-01 - 1 -
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within the range of 1,000 - 500,000.
As can be seen from the above generic description of
the invention, it may be distinguished from the prior art in tha-t
the star-ting polymer, which is subjected to the Mannich reaction
and then quaternized, is a water-soluble crosslinked acrylamide.
In order to prepare the polymers of the invention, the
uncrosslinked acrylamide having the molecular weight ranges
specified above is reacted with from between as little as about
.0005 up to about .1 percent by weight of a preferred divinyl
crosslinking agent, methylene bis acrylamide, to produce a
starting crosslinked polymer that, when further reacted as
described and quaternized, will be shown as having superior
coagulating actlvity over its parent non-crosslinked version.
As indicated, the starting acrylamide polymers are
crosslinked with a divinyl compound such as methylene bisacryl-
amide. The degree of cross-linking may or may not render the
polymers water-insoluble, however, the subsequent Mannich
reaction and quaternization will often bring the insoluble
materials into a suitable range of water solubility. The water
solubility of the polymers may at times becolloidal in nature,
yet if they are sufficiently dispersible, such would come within
the definition of water solubility as described heLein.
While methylene bisacrylamide is a preferred cross-
linking agent, other crosslinking agents such as the diacrylic
acid esters of polyglycols may be used. Any suitable divinyl
compound capable of producing crosslinking of the type achieved
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when methylene bisacrylamide is used can be employed.
The molecularweight of the uncrosslinked polyacryl-
amides as indicated range between 1,000 - 500,000. A preferred
molecular weight range is 2,000 to 200,000.
The Mannich reaction of the crosslinked acrylamide
polymer is accomplished by reacting formaldehyde with a lower
dialkyl amine. The lower dialkyl amines that may be used are
described in U.S. 4,010,131. The preEerred dialkyl amine is
dimethyl amine. The lower alkyl groups should not be greater
than 4 carbon atoms.
The quaternized agents used to quaternize the Mannich
amine crosslinked acrylamide polymer described above may be any
lower alkyl halide or a lower dialkyl sulfate. Such materials
are also described in U.S. 4,010,131. The alkyl group should
not exceed 3 carbon atoms. Preferred quaternizing agen-ts are
either methyl chloride or dimethyl sulfate.
The number of amide groups reacted with the formal-
dehyde and amine may be varied, as is discussed in U.S.
4,010,131.
Exa_ple
To illustrate the invention, the following is presented
by way of example:
A. Polymerization
1. Add the soft water to the glass reactor.
2. With mixing, charge the acrylamide monomer.
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3. Add the required amount of sodium acetate as buffering
agent.
4. Adjust the monomer pH with acetic acid to 5.0 - 5.1.
5. Add N,N'-methylene bisacrylamide as crosslinking
agent. Mix until completely dissolved.
6. Prepare two catalyst solutions, namely sodium
bisulphite and ammonium persulphate, with soft water
in two separate containers.
7. Purge the monomer solution with nitrogen gas for five
minutes.
8. With good mixing, add the ammonium persulphate
solution, followed immediately by sodium bisulphite
solution to the monomer. The polymeriæation reaction
should proceed rapidly and the batch should reach 90 -
100C in five minutes.
9. When the batch temperature starts to subside, maintain
the temperature at 90 - 95C with heating for one hour.
10. After the cook period, cool batch to room temperature
with cooling water.
B. Mannich Reaction
1. When the batch temperature reaches 25C, add the
paraformaldehyde flake with sufficient mixing.
2. With full cooling, immediately add the dimethyl amine
(DMA) solution through a separatory funnel. Do not
delay the addition of dimethyl amine after the
paraformaldehyde has been added. The temperature in
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the reactor must remain below 35 C and so a slow
addition rate is required.
3. When the addition is complete, mix the batch to dissolve
the paraformaldehyde while main-taining batch temperature
at 30 - 35C. After all the paraformaldehyde is
dissolved, mix for one additional hour.
C. Quaternization Reaction with Methyl Chloride
NOTE: This is a high pressure reaction (approximately
100 psig). Make sure that all valves are securely closed.
1. Use a Parr reactor or other stainless steel high pressure
reactor for this reaction.
2. ~efore the pH adjustmen-t, make certain that the methyl
chloride is ready to be used.
3. Cool ba-tch to 25C and adjust pH to 8.0 + 0.1 with
sulphuric acid. Apply cooling and adjust the addition
rate to maintain the batch temperature below 30C.
4. When the desired pH is obtained, shut off all valves so
that the reactor is completely enclosed.
5. Start pumping in the methyl chloride. Adjust the pump
rate to maintain the reactor pressure below 100 psig and
reactor temperature below 35C.
6. After all methyl chloride is in, hold at 35 C for five
to eight hours. Take a sample after each hour to check
on the pH and charge density. The batch is complete
when the batch pH is in the range of 4.3 - 4.7 and charge
density is a minimum of 1.8 meq/g sample.
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FORMULATION OF CROSSLINKED CATIONIC POLYMER
Raw Material % by weight
_A _B _C_ D E
soft water q.s. q.s. q.s. q.s. q.s.
acrylamide 34.26 34.26 34.26 34.26 34.26
sodium acetate 0.25 0.25 0.25 0.25 0.25
acetic acid 0.17 0.17 0.17 0~17 0.17
N,N'-methylene 0.0034 0.0075 0.05 0.03
bisacrylamide
ammonium persulphite 0.0553 0.0553 0.0553 0.0553 0.0553
sodium bisulphite 0.112 0.112 0.112 0.112 0.112
paraformaldehyde 7.76 7.76 7.76 7.76 7.76
dimethyl amine 17.75 17.75 17.75 17.75 17.75
methyl chloride 11.93 11.93 11.93 11.93 11.93
Note: Acrylamide weight % is based on 50% active.
Paraformaldehyde weight gO is based on 91% active.
Dimethyl amine weight % is based on 60% active.
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Polymers A, D~ and ~ were tested ln an industrial
water that contained suspended particles from recycled news-
print. It was basically tested therefore as a de-inking agent.
r~
The results are presented ~ ~t
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