Liquid suspension of polyethylene oxide for use in treating paper and pulp wastewater

A flocculating agent which comprises: a particulate ethylene oxide polymer present in an amount of between about 20 to about 35% by weight; an inert liquid vehicle comprising a mixture of a glycol which is present in an amount between about 25 to about 30% by weight, and glycerine which is present in an amount between about 45 to about 50% by weight, wherein the specific gravity of the ethylene oxide polymer is approximately the same as the specific gravity of the inert liquid vehicle; and a suspension agent which is present in an amount between about 0.4 to about 0.6% by weight, wherein the flocculating agent has a viscosity in the range between about 1800 to about 5900 cps.

The present invention is directed to a unique flocculating agent and a 
process capable of improving the retention and purification of cellulose 
fibre suspensions, and clarification of wastewater generated from the 
paper, pulp and board industries. 
BACKGROUND OF THE INVENTION 
Prior to delivery of paper and pulp wastewater to a dissolved air flotation 
(DAF) unit the wastewater is pre-treated with chemical additives which aid 
in the retention and separation of cellulose fibre suspension, fillers and 
other dispersed particles from the water. 
In the dissolved air flotation process, clarification is achieved by 
forming micron-sized air bubbles in the water-fibre suspension which 
attach themselves to the suspended fibre or ash and float to the surface 
where they can be skimmed off with a mechanical scoop. The air bubbles are 
formed by dissolving air under 60-90 psi pressure. When released to the 
atmosphere in the DAF unit, the gas comes out of solution producing 
bubbles which average 20 microns in size. 
Another advantage of dissolved air is that the lifting action of the 
bubbles tends to concentrate solids at the surface often making it 
possible to recover solids at concentrations of 2-4%. DAF units are 
typically designed such that the aerated mixture is laid in the unit at 
essentially zero velocity. In circular units this is accomplished by 
matching the speed of rotation of the inlet manifold to the flow. This 
minimizes turbulence and cross flow allowing the unit to take full 
advantage of coagulation, flocculation, and the lifting action of the 
bubbles. 
Despite the inherent efficiency of DAF units and recent improvements and 
innovations in design, in most cases it is desirable and cost effective to 
enhance their performance by using synthetic coagulants and flocculants. 
Such polymer additives can increase throughput and aid in the removal of 
fillers such as clay, titanium, and calcium carbonate which are often in a 
highly dispersed state due to the charge balance of the influent. 
Canadian Patent No. 1,004,782 discloses the use of a phenol formaldehyde 
resin in combination with a high molecular weight polyethylene oxide to 
improve the retention at the dewatering of cellulose fibre suspensions. It 
was determined therein that the polyethylene oxide facilitates 
agglomeration of the flocculations formed with the phenol formaldehyde 
resin whereby retention and clarification are facilitated. 
Swedish Patent Publication No. 454,507 (assigned to Berol Kemi Ab) 
discloses that the retention and/or purification of cellulose fibre 
suspensions and clarification of wastewater within the paper, pulp or 
board industry may be improved through pre-treatment with phenol 
formaldehyde resin and high molecular weight polyethylene oxide in 
combination with a cationic starch derivative or a cationic cellulose 
derivative. 
Both of the aforementioned conventional pre-treatment methods utilize a dry 
particulate polyethylene oxide flocculant to facilitate retention and 
clarification. That is, these conventional methods call for the addition 
of polyethylene oxide to wastewater by diluting dry particular 
polyethylene oxide with water to approximately 0.2% by weight immediately 
before addition. 
The present inventors have developed a novel liquid suspension of 
polyethylene oxide which exhibits a much lower viscosity even at a higher 
concentration (based on percent active), i.e., a product which is more 
pumpable and which goes into solution much faster than dry polyethylene 
oxide. Experiments have shown that the novel liquid suspension of 
polyethylene oxide demonstrated a replacement ratio of 2:1 when compared 
to dry polyethylene oxide. It is believed that possible explanations for 
the markedly improved viscosity and flow rates of liquid suspension of 
polyethylene oxide verses dry polyethylene oxide are: (1) more effective 
solubilization of the liquid suspension due to the presence of a wetting 
agent, and (2) shear sensitivity of the polyethylene oxide (i.e., shear 
degradation). That is, liquid suspension of polyethylene oxide facilitates 
solution of the polyethylene oxide particles at a faster rate and higher 
level of activity than the conventional dry feeder approach. 
Although it has not been applied to the treatment of pulp, paper and board 
industry wastewater, U.S. Pat. No. 3,843,589 (Wartman), which issued on 
Oct. 22, 1974, does disclose the forming of a pumpable slurry of 
polyethylene oxide. According to the Wartman patent, a stable slurry 
formulation may be formed by mixing particulate polyethylene oxide, an 
inert liquid vehicle of a glycol and glycerine, and a thickening agent, 
e.g., colloidal silica. This patent was particularly concerned with the 
pumping of polyethylene oxide slurries against a head pressure using some 
type of positive displacement pump, e.g., gear pumps, moyno pumps, and 
diaphragm pumps. These pumping configurations can result in a phenomenon 
called "synaeresis", i.e., liquid carrier medium flows back through the 
clearance while the particles are not free to do so, thus resulting in the 
forward chamber of the pump becoming filled with semi-dry polymer due to 
the backflow of the liquid carrier medium. This liquid suspension exhibits 
high resistance to stratification and molecular weight degradation of the 
active polymer. 
The primary difference between the liquid suspension of polyethylene oxide 
according to the present invention and that disclosed in the Wartman 
patent is that the present invention produces a flocculating agent which 
is suitable for use as a pre-treating aid in paper and pulp wastewater. 
Moreover, the present invention utilizes a suspension agent to assist in 
maintaining the polyethylene oxide in suspension within the inert liquid 
vehicle. It also results in a liquid suspension which has a much lower 
viscosity than that of Wartman, and which is better suited for use as a 
flocculant in the pre-treatment of paper and pulp wastewater. 
One reason for the drastic difference in viscosity is that the Wartman 
patent discloses the use of a thickening agent, such as colloidal silica, 
which does not reduce viscosity as the solids loading is increased. To the 
contrary, the suspension agent used in the flocculating agent of the 
present invention provides for a dramatic reduction in viscosity, 
increased stability and an increased solids loading. 
The present invention also provides many additional advantages which shall 
become apparent as described below. 
SUMMARY OF THE INVENTION 
A flocculating agent which comprises: a particulate ethylene oxide polymer 
present in an amount of between about 20 to about 35% by weight; an inert 
liquid vehicle comprising a mixture of a glycol which is present in an 
amount between about 25 to about 30% by weight, and glycerine which is 
present in an amount between about 45 to about 50% by weight, wherein the 
specific gravity of the ethylene oxide polymer is approximately the same 
as the specific gravity of the inert liquid vehicle; and a suspension 
agent which is present in an amount between about 0.4 to about 0.6% by 
weight. 
The glycol is preferably propylene glycol. The suspension agent comprises a 
mixture of a polymeric fatty acid ester and a dispersing agent. Moreover, 
the flocculating agent has a Brookfield viscosity in the range between 
about 1800 to about 5900 centipoise (cps). 
The specific gravity of the ethylene oxide polymer is in the range between 
about 1.13 to about 1.22, and the specific gravity of the inert liquid 
vehicle is in the range between about 1.11 to about 1.23. 
An additional object of the present invention is a method of treating 
paper, pulp or board wastewater to improve retention and purification of 
cellulose fibre suspensions and clarification of the wastewater. The 
method comprises the addition thereto of a flocculating agent which 
comprises a particulate ethylene oxide polymer present in an amount of 
between about 20 to about 35% by weight, an inert liquid vehicle 
comprising a mixture of a glycol which is present in an amount between 
about 25 to about 30% by weight, and glycerine which is present in an 
amount between about 45 to about 50% by weight, wherein the specific 
gravity of the ethylene oxide polymer is approximately the same as the 
specific gravity of the inert liquid vehicle, and a suspension agent which 
is present in an amount between about 0.4 to about 0.6% by weight. 
The flocculating agent according to this method is used in a concentration 
in the range between about 0.2 to about 0.5%, more preferably in the range 
between about 0.4 to about 0.5%.

Other and further objects, advantages and features of the present invention 
will be understood by reference to the following examples. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Paper, pulp and board wastewater is pre-treated with a liquid suspension of 
polyethylene oxide (i.e., flocculating agent) to improve retention and/or 
purification of cellulose fibre suspensions, and clarification of the 
wastewater. The wastewater is typically pre-treated prior to clarification 
within a dissolved air flotation (DAF) unit where the recovered solids and 
colloidal material are floated to the surface of the DAF unit and skimmed 
off by a mechanical scoop. The resultant clarified water is thereafter 
sent on for further processing. 
Optionally, this flocculating agent is used together with a settling 
clarifier for primary clarification of effluents from a pulp or paper 
production process. 
The flocculating agent comprises: a particulate ethylene oxide polymer 
present in an amount of between about 20 to about 35% by weight; an inert 
liquid vehicle comprising a mixture of a glycol which is present in an 
amount between about 25 to about 30% by weight, and glycerine which is 
present in an amount between about 45 to about 50% by weight; and a 
suspension agent which is present in an amount between about 0.4 to about 
0.6% by weight. 
The ethylene oxide polymer is preferably polyethylene oxide having a 
molecular weight in the range between about 100,000 to about 20,000,000, 
preferably about 5,000,000 to about 20,000,000, more preferably about 
8,000,000 to about 12,000,000. 
The glycol is preferably propylene glycol. Although it is also possible 
that the glycol could also be 1,3-butylene glycol, 1,6-hexylene glycol, 
ethylene glycol, and dipropylene glycol. It is also possible that the 
glycol could be replaced with butyl carbitol. 
It may also be possible to substitute any of the following compositions for 
glycerine 1,2,3,4,5,6 hexane hexol, 1,2,3,4 butane tetrol, pentaerythritol 
and ethylene carbonate. 
The suspension agent comprises a mixture of a polymeric fatty acid ester 
and another dispersing agent. An example of a preferred polymeric fatty 
acid ester is a 40% polymeric fatty acid ester, e.g., Atkemix Hypermer LP6 
sold by ICI. The Atkemix Hypermer LP6 fatty acid ester is preferably 
combined with another dispersing agent such as Atkemix Hypermer PS2 sold 
by ICI. Other potential dispersing agents are stearic monoethanolamide, 
N,N'-ethylene bis stearamide, polyacrylic acid, polyacrylate, and aluminum 
stearate. The suspension agent provides improved wetting, dispersion, 
stabilization and fluidization which can give rise to a variety of effects 
which may be used to advantage in many particulate suspensions. The 
effects of the suspension agent on the liquid suspension of polyethylene 
oxide is a dramatic viscosity reduction, increased stability and increased 
solids loading, i.e., can attain higher percent by weight polyethylene 
oxide than conventional polyethylene suspensions. 
The flocculating agent has a Brookfield viscosity in the range between 
about 1800 to about 5900, and more preferably 1800 to about 3200 cps. The 
specific gravity of the ethylene oxide polymer is approximately the same 
as the specific gravity of the inert liquid vehicle. Specific gravity of 
the ethylene oxide polymer is in the range between about 1.13 to about 
1.22, and the specific gravity of the inert liquid vehicle is in the range 
between about 1.11 to about 1.23. 
The preferred flocculating agent is prepared by initially charging a 
reactor vessel with 27.6% by weight of a propylene glycol and 47% by 
weight of a 95% solution of glycerine with agitation. Cool the mixture to 
approximately 15.degree.-25.degree. C., more preferably between about 
18.degree.-22.degree. C. The use of temperatures above 25.degree. C. can 
result in products which are more viscous than desirable. During mixing, 
accurately charge the reactor vessel with a suspension agent comprising 
0.2% by weight of a 40% polymeric fatty acid ester and 0.2% by weight of a 
dispersing agent. Continue to mix rapidly and slowly charge the reactor 
vessel with 25% by weight of a dry particulate polyethylene oxide. If 
added too rapidly, the polyethylene oxide tends to form lumps in the batch 
which are difficult to break up with mixing. After all of the polyethylene 
oxide is charged into the vessel, mix for an additional hour. 
The flocculating agent prepared above is used in treating paper, pulp or 
board wastewater to improve retention and purification of cellulose fibre 
suspensions, and clarification of the wastewater. The flocculating agent 
is preferably added to the wastewater in a concentration within the range 
between about 0.2 to about 0.5%, more preferably in the range between 
about 0.4 to about 0.5%. This is accomplished by adding the flocculating 
agent to water in a mixing vessel having a blade type of agitator which is 
capable of operating at between 350-400 rpm. 
The following comparative examples where conducted to demonstrate the 
advantages of the liquid suspension of polyethylene oxide according verses 
the conventional dry polyethylene oxide preparations and to determine the 
best formulation of the product. 
EXAMPLES 1-4 
Four samples were prepared and tested for viscosity and flow rate. Sample 1 
is a 0.1% solution of polyethylene oxide prepared from dry particulate 
polyethylene oxide. Sample 2 is a 0.2% solution of polyethylene oxide 
prepared from dry particulate polyethylene oxide. Sample 3 is a 0.4% 
solution of polyethylene oxide prepared from a liquid suspension of 
polyethylene oxide (i.e., flocculating agent) comprising 27.6% by weight 
of propylene glycol, 47% by weight of a 95% solution of glycerine, 0.2% by 
weight of a 40% solution of a polymeric fatty acid ester, 0.2% by weight 
of a dispersing agent, and 35% by weight of a dry particulate polyethylene 
oxide. Sample 4 is an 0.8% solution of polyethylene oxide prepared from 
the liquid suspension of polyethylene oxide describe in sample 3 above. 
The results are set forth in Tables 1 and 2 below. 
TABLE 1 
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[Viscosity Profile @ 350 rpm] 
SAMPLE 
30 sec 
60 sec 
120 sec 
5 min 
10 min 
15 min 
20 min 
25 min 
30 min 
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1 4.9 
11.9 
8.5 
8.0 
8.5 
8.1 
8.5 
8.4 
8.3 
2 5.2 
6.1 
6.9 
7.0 
8.0 
8.4 
8.5 
8.6 
9.0 
3 66.5 
78.4 
23.5 
13.5 
12.0 
12.1 
12.0 
12.0 
12.0 
4 88.0 
192 46.9 
44.1 
40.1 
39.6 
39.5 
39.5 
39.4 
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TABLE 2 
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[Flow Rate: Time for 20 mL to flow through a pipette] 
SAMPLE 
30 sec 
60 sec 
120 sec 
5 min 
10 min 
15 min 
20 min 
25 min 
30 min 
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1 30.4 
40.3 
40.8 
36.9 
35.6 
31.5 
31.1 
30.8 
30.6 
2 32.7 
33.7 
33.5 
32.3 
32.2 
32.9 
33.2 
31.3 
31.7 
3 173.4 
148.1 
84.2 
50.4 
46.0 
45.9 
46.4 
45.4 
44.7 
4 408.0 
305.7 
247.0 
156.0 
111.1 
89.7 
79.2 
71.9 
62.8 
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A lot of insoluble polymer was discovered in beakers of samples 1 and 2 
after 30 minutes. Also, it was determined that the liquid suspension of 
polyethylene oxide in samples 3 and 4 dissolved much faster than the dry 
polyethylene oxide used in samples 1 and 2. The viscosity of sample 3 was 
substantially lower than either of samples 1 or 2, based on concentration. 
EXAMPLES 5-13 
The following samples were prepared in accordance with the above-mentioned 
liquid suspension polyethylene oxide make-up procedure. Samples 5, 6, 7, 
9, and 13 remained stable after three days at 60.degree. C., while samples 
8, 10, 11, and 12 exhibited a slight separation. 
TABLE 3 
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Isoparaffinic 
Heavy Carbopol 934 
Sample 
Glycerine 
Solvent 
Aromatic Naptha 
(polyacrylate) 
PEO 
__________________________________________________________________________ 
5 70 5 -- 1 15 
6 70 10 -- 1 15 
7 70 -- 5 1.8 15 
8 70 5 -- 0.5 15 
9 70 5 -- 0.8 15 
10 75 -- -- 0.8 15 
11 80 -- -- 0.8 20 
12 75 -- -- 0.8 25 
13 70 5 -- 0.5 25 
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None of the aforementioned compositions produced a flocculating agent 
having the retention and clarification characteristics of the polyethylene 
oxide prepared in accordance with sample 3 above. 
EXAMPLE 14 
In order to improve the stability of the liquid suspension of polyethylene 
oxide made in accordance with the aforementioned method, a 1 liter sample 
was prepared from: 
______________________________________ 
27.5% (275 grams) 
of propylene glycol 
47.0% (470 grams) 
of 45% glycerine 
25.0% (250 grams) 
of a dry polyethylene oxide 
0.5% (5 grams) 
of a 40% polymeric fatty acid 
ester suspension agent 
______________________________________ 
Stability of the suspension was improved by the matching of the specific 
gravity of the polyethylene oxide and the combination of propylene 
glycol/glycerine. 
EXAMPLES 15-28 
The following examples were an attempt to determine the proper amount of 
suspension agent which can be added to the liquid suspension of 
polyethylene oxide without making the suspension unstable. 
The liquid suspension set forth in Table 4 below contained 20% by weight of 
dry polyethylene oxide, 29.5% by weight of propylene oxide, 50.5% by 
weight of 45% glycerine, and varying amounts of a suspension agent, i.e., 
40% polymeric fatty acid ester. 
TABLE 4 
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Sample % PEO % Suspension Agent 
Viscosity 
______________________________________ 
15 20 0 1300 
16 20 0.1 2550 
17 20 0.2 2850 
18 20 0.3 3100 
19 20 0.5 3050 
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The suspensions listed in Table 5 below included 25% by weight of 
polyethylene oxide, 27.5% by weight of propylene glycol, 47.5% of 45% 
glycerine, and varying amounts of suspension agent, i.e., a 40% polymeric 
fatty acid ester. 
TABLE 5 
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Sample % PEO % Suspension Agent 
Viscosity 
______________________________________ 
20 25 0 4400 
21 25 0.1 5500 
22 25 0.2 4500 
23 25 0.3 4900 
24 25 0.5 4900 
25 25 0.6 4500 
26 25 0.7 3500 
27 25 0.8 3500 
28 25 0.9 3500 
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Samples 15-18, 20-23 and 27-28 were not stable. Samples 25 and 26 exhibited 
slight separation. And samples 19 and 24, both of which included 0.5% by 
weight of a suspension agent of 40% polymer fatty acid ester, appeared 
stable. As such, samples 19 and 24 were considered satisfactory liquid 
suspensions of polyethylene oxide. It was later discovered that by 
combining the polymeric fatty acid ester with another polymeric 
dispersants such as Atkemix Hypermer PS2 that stable flocculating agents 
can be prepared from a suspension agent present in the range from about 
0.4 to about 0.6% by weight. 
EXAMPLES 29-33 
The samples set forth below in Table 6 appear to demonstrate that liquid 
suspensions of polyethylene oxide can be prepared with dry polyethylene 
oxide in amounts of 30% or more, although such flocculating agents are not 
as stable as those prepared with lesser amounts of PEO. 
TABLE 6 
__________________________________________________________________________ 
Sample 
% PEO 
% Propylene Glycol 
% Glycerine 
% Suspension Agent 
Viscosity 
__________________________________________________________________________ 
29 30 26 44 0.5 7500 
30 30 26 44 0.6 7500 
31 30 26 44 0.7 7500 
32 30 26 44 0.8 8000 
33 30 26 44 1.0 8000 
__________________________________________________________________________ 
EXAMPLE 34 
A flocculating agent was prepared which comprised 27.6% by weight of 
propylene glycol, 47% by weight of glycerine, 25% by weight of dry 
polyethylene oxide, 0.2% by weight of a polymeric fatty acid ester 
(Hypermer LP6), and 0.2% by weight of another dispersing agent (Hypermer 
PS2). This flocculating agent demonstrated a viscosity at 125.degree. C. 
of 1800 cps with a specific gravity of 1.153 and 2200 cps with a specific 
gravity of 1.147. 
It was determined after review of all of the aforementioned data that the 
best formula for producing a stable liquid suspension of polyethylene 
oxide includes an inert liquid vehicle comprising propylene glycol and 
glycerine, dry polyethylene oxide, and a suspension agent which comprises 
a polymeric fatty acid ester and another dispersing agent; wherein the 
specific gravity of the dry polyethylene oxide matches the combined 
specific gravity of the propylene glycol and the dispersing agent. This 
flocculating agent has a viscosity in the range between about 1800 to 
about 5900 cps, more preferably in the range between about 1800 to about 
3200 cps. 
While we have shown and described several embodiments in accordance with 
our invention, it is to be clearly understood that the same are 
susceptible to numerous changes apparent to one skilled in the art. 
Therefore, we do not wish to be limited to the details shown and described 
but intend to show all changes and modifications which come within the 
scope of the appended claims.