Cellulose particles, method for producing them and their use

Cellulose particles are provided which have cationic groups even in the interior.

This invention relates to cellulose particles and to a method for producing 
the same. It further deals with applications of the cellulose particles. 
Due to various measures such as circuit concentration, increased use of 
deinking pulps and high-yield pulps such as wood pulp and TMP 
(thermomechanic pulp), and neutral processing, there has been a rise in 
the load of interfering substances (trash) in the water circuits of the 
paper industry. 
Interfering substances were first defined as all those substances which 
reduce the efficacy of cationic retention aids in the paper stock, i.e. 
those substances added in order to improve the retention of the 
fiber/filler mixture on the wire. Recently this definition has been more 
precisely stated. Interfering substances are thus dissolved or colloidally 
dissolved anionic oligomers or polymers and nonionic hydrocolloids. 
These interfering substances have different effects. They impair the action 
of retention aids, dry- and wet-strength agents, i.e. substances 
increasing the strength of the paper, and furthermore lead to deposits in 
the paper machine circuit, forming and drainage disturbances and a loss of 
paper strength, whiteness and opacity. 
In order to eliminate the adverse effects of these interfering substances 
on papermaking one uses alum, polyaluminum chloride, low- and 
high-molecular fixers, cationic starch and inorganic adsorbents. All these 
substances become attached to the anionic trash with the aid of 
electrostatic interactions and form complexes therewith. Through binding 
of these complexes to the fibers or through filtration effects on the wire 
these aggregates are removed from the paper machine system. 
However all these products have their own disadvantages. For example 
aluminum salts can only be used to a limited extent in neutral processing, 
which is gaining importance due to the increasing use of calcium carbonate 
as a filler, since they are not cationically charged and thus not very 
effective in this pH range. 
The use of highly charged, cationic polyelectrolytes in turn involves the 
problem of exact metering. Otherwise an overcationization of the paper 
machine circuit and thus cationic dispersion can occur. This means that 
there can be poor fine-substance retention and reduced sizing. 
The problem of the invention is to provide new cellulose particles 
characterized by special properties and possible applications. The problem 
of the invention is further to provide cellulose particles which permit 
interfering substances in the paper circuit, machine circuit or water 
circuit to be bound in the paper in the greatest possible quantity and 
thus removed from the circuit without the above-described problems 
occurring. 
The problem of the invention is also to state further possible applications 
of the cellulose particles. 
The invention is based on the finding that this problem can be solved by 
cellulose particles which have cationic groups even in the interior of the 
particles. 
At least 10%, preferably at least 50%, in particular at least 90%, of the 
cationic groups are thereby generally present in the interior of the 
particles. As a result cellulose particles are thus provided which have 
cationic groups bound to the cellulose distributed over the total cross 
section of the particles. 
So that the particles have sufficient cationicity, at least one cationic 
group should be present per 100, preferably per 50, anhydroglucose units 
of the cellulose. 
For producing the inventive cellulose particles one reacts the cellulose 
with a cationizing agent. 
The cellulose used can be unsubstituted pulp but also substituted 
celluloses, in particular cellulose ester or ether such as methyl 
cellulose, carboxymethylcellulose, cellulose sulfate, cellulose acetate or 
chitosan. The degree of substitution (DS) should be smaller than 1, that 
is, no more than one of the three OH groups of the anhydroglucose units of 
the cellulose should be substituted on the average. The DS must not be too 
great so that a sufficient number of hydroxyl groups are available for 
reaction with the cationizing agent. Further, alkali cellulose, in 
particular sodium cellulose, can be used as cellulose. 
The reaction of the cellulose with the cationizing agent can be performed 
as a solids reaction. The cellulose used can be alkali cellulose which is 
reacted with the cationizing agent in a kneader. 
For producing the inventive cellulose particles the cellulose can also be 
dissolved and the dissolved cellulose mixed with the cationizing agent, 
whereupon the cationized dissolved cellulose is precipitated into the 
cellulose particles. 
Dissolving the cellulose can be done by converting the cellulose with 
sodium hydroxide solution and carbon disulfide into sodium xanthogenate, 
but also by dissolving it in N-methylmorpholine-N-oxide, lithium chloride 
dimethylacetamide, tetraammine copper copper(II) hydroxide, 
cupriethylenediamine or cuprammonium. 
N-methylmorpholine-N-oxide monohydrate has a melting point of about 
70.degree. C. It can therefore be recovered easily as solids. In contrast 
to xanthogenate, no bad smell occurs and no waste materials such as sodium 
sulfate are obtained. 
In the case of water-soluble cellulose derivatives one can use water as a 
solvent. Water-soluble cellulose derivatives are preferably prepared by 
the viscose process. 
The cationic groups can be bound covalently to the hydroxyl groups of the 
cellulose. However a bond via ionic and/or hydrogen bridges is also 
possible. 
The cationizing agents used can be aluminum salts such as polyaluminum 
chloride or sodium aluminate. The polyaluminum chloride can be partly 
hydrolyzed. The aluminate is precipitated together with the xanthogenate 
with sulfuric acid. 
The cationizing agents used can further be cationic polyelectrolytes, such 
as polydialkyldiallylammonium salts, in particular 
polydialkyldiallylammonium chloride (poly-DADMAC), dicyandiamide, 
dicyandiamide condensate, polyamines, polyimines such as polyethylene 
imine, or ionenes. The cationizing agents used can further be reactive 
monomers, for example primary, secondary and tertiary amines, quaternary 
ammonium bases each with at least one residue reacting with a hydroxyl 
group of the cellulose. 
If the cationizing agent does not react with the hydroxyl groups of the 
anhydroglucose units of the cellulose, as in the case of aluminum salts 
and cationic polyelectrolytes, the solubility of the cellulose does not 
change much or at all. In this case the ratio of cationizing agent to 
cellulose can fluctuate within wide limits. Normally, however, the weight 
ratio of aluminum salts or cationic polyelectrolytes to cellulose is 
between 0.03:1 to 1:1 based on the absolutely dry substances (abs. dry). 
The reactive monomers, however, are preferably added to the cellulose in a 
quantity such that the degree of substitution (DS) is no more than 0.2. 
Otherwise cellulose particles with excessive water solubility can arise. 
The cationizing agent with reactive groups, i.e. reactive monomers, used 
can be in particular 2-chloroethane trimethylammonium chloride or 
propoxytrimethylammonium chloride. 
By precipitating dissolved cellulose with a high degree of substitution, 
for example carboxymethylcellulose, in an aqueous solution with cationic 
polyelectrolytes one can likewise obtain the inventive cationized 
cellulose particles. 
Since the cationic charges in the inventive cellulose particles are fixed 
predominantly in the interior of the particles, one can beat (grind) the 
particles to make further charges accessible which can act as functional 
groups. 
If reactive monomers are used as a cationizing agent the reactive groups 
are residues reacting with cellulose hydroxyl groups. The reacting residue 
can be for example a halogen atom, epoxy groups or imino groups. In order 
to form an epoxy group, a halogen atom can for example be bound to one 
carbon atom, and a hydroxyl group to the adjacent carbon atom, of an alkyl 
residue of the amine or quaternary amronium base. For example the ammonium 
compound can be 3-chloro-2-(hydroxypropyl)-trimethylammonium chloride. 
In order to prevent crosslinking of individual cellulose fibers in 
particular in the case of dicyandiamide and other polyelectrolytes, the 
cellulose can be reacted in relatively high dilution with the cationizing 
agent. That is, when mixed with the cationizing agent the dissolved 
cellulose is present in a concentration of preferably no more than 2 
percent by weight, in particular no more than 1 percent by weight. 
Reacting the dissolved cellulose with the cationizing agent is preferably 
done with stirring, in a time period of for example 10 seconds to 30 
minutes depending on the reactivity of the cationizing agent. If the 
reaction time is too long there is the abovementioned danger of 
crosslinking. 
Precipitating the dissolved cationized cellulose can be done for example 
through fine spinning jets in precipitation baths. 
If the dissolved cellulose used is cellulose xanthogenate, the precipitant 
can be for example a polyaluminum chloride or sulfuric acid, whereby the 
sulfuric acid may optionally have salts, e.g. a sulfate such as sodium or 
zinc sulfate, added. 
As has turned out, the cellulose particles can also be obtained by adding a 
precipitant to the dissolved cationized cellulose with stirring and thus 
causing precipitation directly in the reactor. 
The size of the cellulose particles, or the length of the precipitated 
cellulose fibers, is then dependent on, among other things, the dilution 
of the dissolved cationized cellulose and the stirring rate during 
precipitation. 
The particles of cationized cellulose preferably have a mean particle size 
of 0.001 to 10 mm, in particular a mean particle size of 0.1 to 1 mm. The 
particles are preferably spherical. However they can also exist in the 
form of fibers. 
A desired size and structure of the cellulose particles can in particular 
also be obtained by beating. 
For comminuting the cellulose particles one can use a great variety of 
beating apparatuses, in particular standard devices for pulp beating such 
as a Jokro mill, conical refiner or disk refiner. The beaters customarily 
used for beating paper fibers are also very suitable. Beating causes a 
substantial enlargement of the cellulose particle surface and thus 
increased cationicity and efficacy. 
The single figure shows cellulose particles in a dark field image. The 
particles are in a swollen state. The particles are actually spherical in 
three dimensions but they are squeezed between the slides in the picture. 
The enlargement factor is 100. The random fibril structure with fibrils in 
the range of 10 to 50 microns is easily recognized. 
When the cellulose particles are used in papermaking the particle size must 
obviously not be thicker than the paper thickness, while a fiber structure 
can be advantageous. 
When the cationized cellulose fibers are used as a means for fixing the 
interfering substances in the paper they should not be longer than 0.5 mm 
in order to rule out forming problems. The cationized cellulose fibers are 
preferably no longer than 0.1 mm. 
For other applications, e.g. as a flocculant, in particular a flocculant 
for waste-water purification, a mean particle size of 0.1 to 1 mm is 
usually preferred. 
The cellulose particles are used as a solid or in the form of a suspension. 
The inventive cellulose particles can be termed water-insoluble. This means 
that the cellulose particles virtually do not dissolve in water in the 
usual dwell times and application methods. The dwell times are in the 
range of minutes. 
In the inventive cellulose particles the cationic groups are bound 
covalently to the cellulose or immobilized within the cellulose membrane. 
This covalent bond or immobilization prevents any relevant loss of 
cationic activity during use of the cellulose particles. 
The inventive cellulose particles are used as solids, whereby they can 
contain up to 80% water. It is also conceivable to dry these cellulose 
particles and use them as dry granules. Alternatively one can use them in 
the form of a suspension, for example with 3% solids content, or in the 
form of a paste with higher solids contents up to 20%. 
After precipitation of the dissolved cationized cellulose polymer chains 
the cationic groups are contained in the cellulose particles uniformly 
distributed over the total cross section thereof. 
The cationic groups present in the interior of the cellulose particles are 
insensitive to mechanical action, being e.g. not removed by the shear 
forces caused by stirring. 
The inventive cationized cellulose particles are an outstanding means for 
fixing interfering substances in the paper which are present in the water 
circuits during papermaking. 
Use of the cationic cellulose has no adverse effect on the paper 
properties, unlike known means for fixing interfering substances in the 
paper such as bentonite. 
At the same time the inventive cationized cellulose causes the fine 
substances, in particular the fine filler particles, to bind with the 
fibers, thereby improving the fine-substance or ash retention and the 
distribution of fine substances in the paper and obtaining a more 
homogeneous sheet. That is, the inventive canionized cellulose permits the 
fine substances to be retained both on the side of the cellulose 
particle/filler mixture facing the wire and on the upper side. 
Above all else, however, the inventive cationized cellulose causes anionic 
trash, which (as mentioned above) occurs in greater quantity in the paper 
machine circuit nowadays, to bond with the cellulose particles of the 
cellulose particle/filler mixture and thus be discharged from the circuit. 
In particular when the inventive cationized cellulose fiber is short, i.e. 
has a length of e.g. 0.1 mm or less, this in addition demonstrably 
increases the strength of filled paper, a crucial property for judging 
paper quality. This is possibly due to the fact that short cationized 
cellulose particles collect in the spaces between longer cellulose fibers 
of the paper and form bridges there between the cellulose fibers of the 
paper. 
In the paper industry the inventive cationized cellulose particles can thus 
be used as a strength-increasing means for filled paper or as a means for 
fixing interfering substances in the paper, thereby removing these 
interfering substances from the water circuit. 
Furthermore the inventive cationized cellulose particles are a means for 
retaining fine substances in the paper during papermaking. That is, fine 
ash or other filler particles or other fine solids particles which are to 
be incorporated in the paper are retained by the inventive cationized 
cellulose particles, i.e. protected from being washed out and thus kept in 
the paper. This achieves increased homogeneity and dimensional stability 
of the paper. Since the fine substances are bound better, this at the same 
time reduces the tendency to dust during processing (f the paper. In 
addition the inventive cationized cellulose particles lead to an increase 
in strength in filled paper. 
The invention thus includes in particular a method for producing paper 
using a closed water circuit to which the inventive cellulose particles 
are added. The interfering substances are thereby bound and rendered 
harmless. One generally adds 0.1 kg of cationized cellulose particles per 
ton of paper stock (abs. dry). The upper limit is generally 10 kg/ton for 
reasons of cost. 
At the same time the inventive cationized cellulose particles are an 
outstanding flocculation aid for poorly precipitable organic sludges. The 
inventive cationized cellulose particles can thus be used in particular as 
a flocculant for waste-water purification, above all in clarification 
plants for flocculating digested sludge. Compared to conventional 
flocculants, in particular polyelectrolytes, the inventive cationized 
cellulose particles have a greatly enlarged, stable cationic surface on 
which the substances to be flocculated can be precipitated. In contrast to 
conventional flocculants one thus obtains a more stable floc which can 
also be dewatered better. 
It has turned out that use of the inventive cellulose particles in 
combination with water-soluble polymers produces surprising results, both 
when the cellulose particles are used in sludge drying and when they are 
used in papermaking. 
Especially good results are achieved in combination with cationic, 
water-soluble polymers. However combinations with anionic or nonionic 
polymers are also conceivable. 
An especially advantageous combination has turned out to be the combination 
of the inventive cellulose particles with water-soluble cationic 
polyacrylamide. Along with polyacrylamide one can in particular use 
polyethylene imine and water-soluble cellulose derivatives, for example 
cationic hydroxyethylcelluloses or carboxymethylcelluloses. 
In sludge drying the inventive, water-insoluble cellulose particles are 
preferably added in mixture with the water-soluble polymers. However 
separate addition is equally possible. 
Based on the water-soluble polymer, for example polyacrylamide, the 
addition of inventive cellulose particles can be within very wide limits 
from 0.1 to 99.9 wt %. However preferred weight percentages of cellulose 
particles are 1 to 50% preferably 1 to 10%, particularly 2 to 7% and in 
particular 3 to 5%. The percentage of cellulose particles is determined by 
the sludge quality, the desired dry content of the sludge and the 
throughput capacity. 
When the inventive cellulose particles are used in combination with a 
cationic polymer, the two components are preferably premixed, stored and 
transported dry. Before application, the mixture is dissolved or dispersed 
in water and charged to the sludge directly without filtration, which is 
unnecessary for sludge. 
This preferred use of the mixture of cellulose particles and polymers is 
only possible with cationic polymers, not with anionic polymers, since the 
latter would react with the cationic cellulose particles. Anionic polymers 
are therefore added separately from the cellulose particles. 
When the inventive cellulose particles are used in combination with anionic 
polymer, the cellulose particles are stored, transported, prepared and 
metered separately, in a dry form or in the form of an aqueous suspension. 
The anionic polymer can likewise be stored and transported dry, dissolved 
in water, or as an emulsion. In any case the two components must be 
charged to the sludge separately as an aqueous solution or a suspension. 
One can use either possibility of charging, first cellulose particles or 
first polymer. 
The synergistic effect obtained by the combination of water-soluble 
polymers and water-insoluble cellulose particles is impressive. The 
mechanism of action is unknown, however. For example, tests with 
biological sludge have shown that the use of 94.3 wt % polyacrylamide and 
5.7 wt % cellulose particles, rather than the use of pure polyacrylamide, 
allows an increase in speed of the band press of 62 to 100% and an 
increase in sludge throughput of 28 m.sup.3 /h to 33 m.sup.3 /h. 
Other tests aimed at a higher dry content have also shown impressive 
results. Thus the addition of only 3 wt % cellulose particles to the 
polyacrylamide used resulted in an increase in dry content after pressing 
of 48 to 53%. 
The combined use of cationic, water-soluble polymers and the inventive 
water-insoluble cellulose particles has also shown surprising results 
particularly in papermaking. 
In papermaking a separate addition of cellulose particles and water-soluble 
polymers is preferred. It is advantageous to filter the water-soluble 
polymer as a solution continuously before the metering point in order to 
filter out gel particles impairing paper quality. It is better to add the 
cellulose particles before and the water-soluble polymers only later. In 
particular it is advantageous to add the cellulose particles in the 
initial phase of papermaking, while the water-soluble polymers are added 
in the final phase shortly before sheet formation. 
Expressed as time history and assuming a total circulating time of about 90 
seconds, the cellulose particles are added in 30 to 60 seconds before the 
feed of the paper stock to the headbox, and the water-soluble polymers 
about 10 to 20 seconds before. 
The mixture ratio of cellulose particles and cationic polymers is variable 
within wide limits, for example from 90:10 to 10:90. However it is 
preferable to add 40 to 60% cellulose particles based on weight. The 
preferred quantity depends on the grade of paper, among other things. 
Higher percentages are preferred for paper with little filler. 
In papermaking, the cellulose particles are preferably added in the form of 
a suspension in water, for example a 3% suspension. The polymer solution 
is added as an aqueous solution, for example in a concentration of 0.2 to 
0.8%. 
When anionic water-soluble polymers are used in combination with cellulose 
particles the same mixture ratios and manners of addition or adding times 
are preferred. 
It has turned out that use of the inventive cellulose particles in 
papermaking can achieve greater quantities of filler in the paper. This is 
desirable for economic reasons since fillers are cheaper than paper 
fibers. Fillers achieve better properties, in particular improved opacity 
and printability. 
A further advantage which has emerged from the addition of cellulose 
particles is improved forming of the paper and thus improved paper 
quality. 
The term "cellulose particles" also refers in this patent application to 
fibers of any form and length, in particular spun fibers. Cellulose fibers 
have diverse applications in the industrial and textile field. 
The special feature of the inventive fibrous cellulose particles is their 
greatly improved dyeing behavior. In particular the fibers can be dyed 
with favorable anionic dyes. The dyed fibers are characterized by 
particular color fastness, which is due to one fact that the cationic 
groups reacting with the dyes are immobilized in the cellulose fiber or 
bound covalently to the cellulose molecules.

The following examples will explain the invention further. 
EXAMPLE 1 
An 8.5 weight percent, aqueous sodium cellulose xanthogenate solution is 
diluted with 0.02 N sodium hydroxide in a ratio of 1:25. 
250 ml of the diluted sodium cellulose xanthogenate solution is mixed with 
stirring (350. rpm) with 1 ml of a 40 weight percent, aqueous solution of 
dicyandiamide. 
After five minute of stirring the speed is increased (600 rpm), whereupon 5 
ml of an 18 weight percent, aqueous polyaluminum chloride solution is 
added dropwise. 
The precipitated cellulose fibers are washed with water until the 
supernatant has no more cationic charges. 
EXAMPLE 2 
100 kg of pulp is converted with 18% aqueous sodium hydroxide into alkali 
cellulose (AC). 20 kg of 3-Cl-2-hydroxypropanetrimethylammonium chloride 
is added to the pressed AC. The reaction is performed in the kneader with 
cooling at 35.degree. C. for 6 hours. Then neutralizing is done with 
hydrochloric acid and washing with water. The obtained cationized 
cellulose is dried and beaten to the necessary particle size. 
EXAMPLE 3 
To detect the cationicity of the cellulose fibers obtained in Example 1 one 
uses methyl red as an anionic dye. The cationicity of conventional 
precipitated, unmodified cellulose fibers was compared with the cationized 
cellulose fibers produced according to Example 1. The fibers were mixed 
for this purpose with the methyl red solution and then centrifuged. After 
centrifugation, the color of the fibers and the coloration of the 
supernatant were judged. 
In the cationized cellulose fibers produced according to Example 1 there 
was a clear coloration of the fibers and at the same time a decolorization 
of the supernatant, in contrast to unmodified cellulose fibers. 
As a control, methylene blue was used as a cationic dye. With the weakly 
anionic unmodified cellulose fibers a coloration of the fibers was 
observed, while the cationized cellulose fibers produced according to 
Example 1 did not color. Also, in the cationized fibers there was no 
decolorization of the supernatant. 
EXAMPLE 4 
To check the efficacy of the cellulose fibers produced according to Example 
1, paper stock from a woody and ashy production (raw material for natural 
rotogravure) was mixed with the cationic cellulose fibers produced 
according to Example 1, whereby sheets were formed by the standard method. 
Sheet weight, bursting pressure, tear propagation strength and forming in 
the paper were judged. It turned out that the cationized cellulose fibers 
produced according to Example 1 had a positive influence on the 
distribution of fine subscances, including the ash distribution, and the 
strength and forming in comparison to a simultaneously performed 
comparative test (without addition of such cationized fibers). 
EXAMPLE 5 
With cationized cellulose fibers produced according to Example 1 with an 
average length of about 4 cm, a flocculation test was performed with 
digested sludge from a waste-water clarification plant which is difficult 
to flocculate since it is very fine. It turned out that the cationized 
cellulose fibers yielded good flocculation, a high settling rate and a 
clear supernatant, whereas a comparative test with a conventional 
flocculant, namely polyacrylamide, showed only little flocculation. 
EXAMPLE 6 
An 8.5 weight percent aqueous solution of sodium cellulose xanthogenate was 
diluted with an aqueous solution of sodium hydroxide (4 g/l) to 4.25% (as 
cellulose). 
The cationizing agent, a 40% aqueous solution of a dicyandiamide 
formaldehyde condensate resin (a commercially available product from SKW 
Trostberg, MELFLOCK C3), was diluted with water to 2 weight percent active 
concentration. 
600 ml of the above diluted 2% dicyandiamide formaldehyde condensate resin 
solution was stirred with a stirrer at 750 rpm and then 940 ml of the 
above sodium cellulose xanthogenate solution, diluted to 4.25%, was slowly 
added to the stirred cationizing agent. 
This mixture already containing precipitated particles was then slowly 
added to the precipitation bath. The precipitation bath consisted of 3000 
ml of aqueous solution containing 35 g of sulfuric acid (98%), which was 
likewise continually stirred. In this precipitation bath there was a 
quantitative precipitation of the product. More acid was added if 
necessary to ensure a pH of less than 2. 
The precipitated, fibrous product was filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, taken up and shaken in 1000 ml of 
deionized water. The pH was adjusted to between 4.5 and 5.5 with diluted 
sodium hydroxide solution. 
The precipitated product was once again filtered out through a 
filter-funnel fitted with a fine plastic gauze sieve, repeatedly taken up 
and shaken in 1000 ml of deionized water and filtered until no significant 
further cationicity could be detected in the supernatant. 
During this washing stage, the residual cationicity, if any, was measured 
by titrating an aliquot against a standardized anionic polymer with a 
particle charge detector (.mu.Tek PCD 02), or detected by a suitable dye 
(ortho-toluidine blue) as an indicator. 
The wet product (solids content approximately 12 to 20%) was removed from 
the filter and then stored in this state. 
EXAMPLE 7 
An 8.5 weight percent aqueous solution of sodium cellulose xanthogenate was 
diluted with aqueous sodium hydroxide solution (4 g/l) to 1% (as 
cellulose). 
The cationizing agent, a 40% aqueous solution of a 
polydiallyldimethylammonium chloride (a commercially available product, 
FLOERGER FL 45 C), was diluted with water to 1 weight percent active 
concentration. 
2000 ml of che above sodium cellulose xanthogenate solution diluted to 1% 
was stirred with a high-shear stirrer without allowing air to be drawn 
into the solution. 600 ml of the above 1% polydiallyldimethylammonium 
chloride solution was subsequently added to the stirred solution over a 30 
second period. The resultant mixture was stirred vigorously for one 
further minute. 
The reaction of the cationizing agent with the cellulose xanthogenate 
solution causes an immediate and increasing rise in viscosity in the 
mixture. If, for example, the undiluted substances viscose and poly-DADMAC 
are mixed together (at the above solids contents) the mixture immediately 
solidifies, subsequently separating to a solid phase and a liquid phase. 
1000 ml of an aqueous solution containing 25 g of sulfuric acid (98%) was 
added to the stirred mixture and the precipitation thus completed. More 
acid was added if necessary to ensure a pH of less than 2. 
The precipitated, fibrous product was filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, taken up and shaken in 500 ml of 
deionized water. The pH was adjusted to 4.5 to 5.5 with diluted sodium 
hydroxide solution. 
The precipitated product was again filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, repeatedly taken up and shaken in 
500 ml of deionized water and filtered until no significant cationicity 
could be detected in the supernatant. 
During this washing stage, the residual cationicity, if any, was measured 
by titrating an aliquot against a standardized anionic polymer with a 
particle charge detector (.mu.Tek PCD 02), or detected by a suitable dye 
(ortho-toluidine blue) as an indicator. 
The wet product (solids content approximately 12 to 20%) was removed from 
the filter and then stored in this state. 
EXAMPLE 8 
The same procedure as Example 6 was also conducted with a different 
cationizing agent, a 20 weight percent solution of polyethylene imine (a 
commercially available product from BASF, POLYMIN SK). The polyethylene 
imine solution was diluted with water to 2% concentration. 600 ml of this 
diluted cationizing agent solution was used in the reaction. 
EXAMPLE 9 
The same procedure as Example 6 was also conducted with a different 
cationizing agent, a 50 weight percent aqueous solution of a polyamine (a 
commercially available product, FLOERGER FL 17). The polyamine solution 
was diluted with water to 2% concentration. 600 ml of this diluted 
cationizing agent solution was used in the reaction. 
EXAMPLE 10 
An 8.5 weight percent aqueous solution of sodium cellulose xanthogenate was 
diluted with aqueous sodium hydroxide solution (4 g/l) to 4.25% (as 
cellulose). 
The cationizing agent, a solution of reactive, cationic monomers (a 
commercially available product from Raisio, RAISACAT 65), comprised the 
following ingredients (approximately 70% concentration): 
______________________________________ 
1) 3-Chloro-2-hydroxypropyl-trimethylammonium chloride 
ca. 2% 
2) 2,3-Epoxypropyl-trimethylammonium chloride 
ca. 66% 
3) 2,3-Dihydroxypropyl-trimethylammonium chloride 
ca. 3% 
______________________________________ 
2,2 g of the commercial product was diluted to 200 ml with deionized water. 
470 ml of the above sodium cellulose xanthogenate solution diluted to 4.25% 
was stirred at 800 rpm with a propeller stirrer without allowing air to be 
drawn into the solution. 200 ml of the above diluted cationizing agent 
solution was subsequently added over a 30 second period into the stirred 
solution. The resultant mixture was stirred for a further 30 minutes. 
670 ml of an aqueous solution containing 18 g of sulfuric acid (98%) was 
added to the stirred mixture and the precipitation thus completed. More 
acid was added if necessary to ensure a pH of less than 2. 
The precipitated, fibrous product was filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, taken up and shaken in 500 ml of 
deionized water. The pH was adjusted to 4.5 to 5.5 with diluted sodium 
hydroxide solution. 
The precipitated product was once again filtered out through a 
filter-funnel fitted with a fine plastic gauze sieve, repeatedly taken up 
and shaken in 500 ml of deionized water and filtered until no significant 
further cationicity could be detected. 
During this washing stage, the residual cationicity, if any, was measured 
by titrating an aliquot against a standardized anionic polymer solution 
with a particle charge detector (.mu.Tek PCD 02), or detected by a 
suitable dye (ortho-toluidine blue) as an indicator. 
The wet product (solids content approximately 12 to 20%) was removed from 
the filter and then stored in this state. 
EXAMPLE 11 
The same procedure as Example 7 was also conducted with a different 
cationizing agent, a 40 weight percent aqueous solution of a special, 
highly branched, polydiallyldimethylammonium chloride. The 
polydiallyldimethylammonium chloride was diluted with water as in Example 
7. 
EXAMPLE 12 
The same procedure as Example 7 was also conducted with a different 
cationizing agent, a 48.5 weight percent aqueous solution of a special, 
low-molecular polydiallyldimethylammonium chloride. The 
polydiallyldimethylammonium chloride was diluted with water to 1% 
concentration as in Example 7. 
EXAMPLE 13 
The same procedure as Example 6 was also conducted with a different 
cationizing agent, a 40 weight percent solution of a copolymer of 
diallyldimethylammonium chloride and acrylic acid, the monomer component 
acrylic acid constituting less than 10%. The copolymer solution was 
diluted with water to 1% concentration in this example. 
EXAMPLE 14 
An 8.5 weight percent aqueous solution of sodium cellulose xanthogenate was 
diluted with aqueous sodium hydroxide solution (4 g/l) to 2% (as 
cellulose). 
The cationizing agent, a 29% aqueous solution of a polyaluminum chloride (a 
commercially available product from Ekokemi, EKOFLOCK 70), was used in 
undiluted form. 
1000 ml of the above sodium cellulose xanthogenate solution diluted to 2% 
(as cellulose) was stirred with a propeller stirrer vigorously but without 
allowing air to be drawn into the solution. 21 ml of the above undiluted 
cationizing agent solution was subsequently added to the stirred solution 
over a 30 second period. The resultant mixture was stirred vigorously for 
one further minute. 
1000 ml of an aqueous solution containing 20 g of sulfuric acid (98%) was 
added to the stirred mixture and the precipitation thus completed. More 
acid was added if necessary to ensure a pH of less than 2. 
The precipitated, fibrous product was filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, taken up and shaken in 500 ml of 
deionized water. The pH was adjusted to 3 to 4 with diluted sodium 
hydroxide solution. 
The precipitated product was once again filtered out through a 
filter-funnel fitted with a fine plastic gauze sieve, repeatedly taken up 
and shaken in 500 ml of deionized water and filtered. 
The wet product (solids content approximately 12 to 20%) was removed from 
the filter and then stored in this state. 
EXAMPLE 15 
An 8.5 weight percent aqueous solution of sodium cellulose xanthogenate was 
diluted with aqueous sodium hydroxide solution (4 g/l) to 2% (as 
cellulose). 
The cationizing agent, a 45% aqueous solution of a sodium aluminate (a 
commercially available product from Mare, FIMAR A 2527), was used in 
undiluted form. 
1000 ml of the above sodium cellulose xanthogenate solution diluted to 2% 
was stirred with a propeller stirrer vigorously but without allowing air 
to be drawn into the solution. 24 ml of the above undiluted cationizing 
agent solution was subsequently added to the stirred solution over a 30 
second period. The resultant mixture was stirred vigorously for one 
further minute. 
1000 ml of an aqueous solution containing 37 g of sulfuric acid (98%) was 
then added to the stirred mixture and the precipitation thus completed. 
More acid was added if necessary to ensure a pH of less than 2. 
The precipitated, fibrous product was filtered out through a filter-funnel 
fitted with a fine plastic gauze sieve, taken up and shaken in 500 ml of 
deionized water. The pH was adjusted to 3 to 4 with diluted sodium 
hydroxide solution. 
The precipitated product was once again filtered out through a 
filter-funnel fitted with a fine plastic gauze sieve, repeatedly taken up 
and shaken in 500 ml of deionized water and filtered. The wet product 
(solids content approximately 12 to 20%) was removed from the filter and 
then stored in this state. 
EXAMPLE 16 
The same procedure as Example 7 was also conducted with a modified 
cellulose (sodium methyl cellulose xanthogenate). Low-substituted, 
water-insoluble methyl cellulose was used instead of the unmodified 
cellulose. 
EXAMPLE 17 
A solution of cellulose in lithium chloride, dimethyl acetamide (DMA) and 
water is prepared as follows. 
Cellulose pulp which has been bleached and stored moist is added to a 
mixture of lithium chloride and dimethyl acetamide so that the components 
are present in the following ratio: 5 parts cellulose (dry weight), 11 
parts lithium chloride, 82 parts dimethyl acetamide and some water (from 
the moist pulp). 
This mixture is homogenized with a high-shear stirrer, and heated under 
vacuum over a water bath until the water content of the mixture is less 
than 3%. A dry nitrogen trickle-sparge is used to aid water removal. 
The resultant suspension is cooled in a refrigerator to 5.degree. C. and 
held for a day at this temperature. Periodic stirring aids dissolution of 
the suspended cellulose. The resultant solution is warmed to 50.degree. C. 
and filtered through a fine sieve. 
A 40 weight percent, aqueous solution of a polydiallyldimethylammonium 
chloride (a commercially available product, FLOERGER FL 45 C) is used as 
the cationizing agent. 
Based on dissolved cellulose, 10% cationizing agent (as an active 
substance) in undiluted form is added slowly with continuous mixing. The 
small amount of water introduced into the solution with the cationizing 
agent normally does not interfere with the solution equilibrium of 
cellulose-lithium chloride-dimethylacetamine-water so that the cellulose 
does not precipitate but the viscosity of the resultant mixture begins 
rapidly to rise and the next stage follows immediately. 
The resultant mixture, at a temperature of 50.degree. C., is poured into 
the vortex region of a stirred aqueous precipitation bath whereby the 
cationized cellulose precipitates out. 
The precipitated, fibrous product is filtered out of the mixture through a 
filter-funnel fitted with a fine plastic gauze sieve. 
The filtered out product is shaken in deionized water and refiltered. This 
washing process removes residual amounts of salts and DMA from the 
product. 
The product is once again washed with deionized water and filtered. This 
process is repeated until no significant further cationicity in the 
filtrate water can be detected. 
The wet product (solids content approximately 12 to 20%) is removed from 
the filter and then stored in this state. 
EXAMPLE 18 
A solution of cellulose in N-methylmorpholine-oxide (NMMO) was prepared as 
follows. 
An NMMO/water mixture is analyzed for water content. This is normally 
around 30% water at this stage. 
Pure cellulose in powder form was added to the above mixture at a level to 
give 3.6 weight percent (based on NMMO). This mixture was then placed in a 
vacuum flask fitted with a stirrer and a sparge pipe which is used to 
trickle-feed dry nitrogen gas under the liquid surface. The flask was then 
heated to 95.degree. C. in a water bath. A vacuum was applied, the stirrer 
was turned on and a small quantity of nitrogen was allowed to bubble 
through the liquid phase, thus progressively removing water. 
At a certain concentration of water and NMMO (approx. 88% NMMO) the 
cellulose dissolves. The nitrogen purge and vacuum pump were then stopped. 
In this experiment a 40% solution of a polydiallyldimethylammonium 
chloride (a commercially available product, FLOERGER FL 45 C) was used as 
a cationizing agent. 
Based on dissolved cellulose, 10% cationizing agent (as an active 
substance) was added in undiluted form to the cellulose solution with 
stirring. The small amount of water (approximately 0.5%) introduced into 
the NMMO solution by the cationizing agent normally does not alter the 
solution equilibrium of cellulose-NMMO/water as to cause precipitation of 
the cellulose. 
The resultant mixture was pumped using a gear-wheel pump through a glass 
wool packed filter and then through a spinning jet into a water bath, 
where the cationized cellulose coagulated and could be formed into fibers. 
These fibers were filtered off, washed and dried and then cut to 
approximately 1 cm length. 
EXAMPLE 19 
A 2 weight percent aqueous solution of carboxymethylcellulose (CMC) having 
a degree of substitution of approximately 0.55 was prepared and stirred 
for one hour to ensure complete dissolution of the CMC. 
The canionizing agent, a 40% aqueous of a dicyandiamide formaldehyde 
condensate resin (commercially available from SKW Trostberg, MELFLOCK C3), 
was diluted with water to 4 weight percent concentration. 
1000 ml of the above 2% CMC solution was stirred at 800 rpm with a 
propeller stirrer and 125 ml of the above aqueous solution of 
dicyandiamide formaldehyde condensate resin diluted to 4% was subsequently 
added in a 10 second period. This mixture already containing precipitated 
cationized cellulose was stirred for a further 5 minutes. 
The precipitated product was filtered out through a filter-funnel fitted 
with a fine plastic gauze sieve, repeatedly taken up and shaken in 500 ml 
of deionized water and filtered until no significant further cationicity 
could be detected in the supernatant. 
During this washing stage, the residual cationicity, if any, was measured 
by titrating an aliquot against a standardized anionic polymer solution 
with a particle charge detector (.mu.Tek PCD 02), or detected by a 
suitable dye (ortho-toluidine blue) as an indicator. 
The wet product (solids content approximately 12 to 20%) was removed from 
the filter and then stored in this state. 
EXAMPLE 20 
The solids content of the cationized cellulose from Example 6 was measured. 
Enough of the wet product to give 10 g of dry product was taken and made 
up to 200 g with water. This dispersion was transferred to a Jokro mill 
and beaten for 10 minutes at 1500 rpm. This type of mill is normally used 
in a paper laboratory to test the beating characteristics of fibers for 
papermaking. The above beating parameters are comparable to those used for 
testing firers for papermaking. 
The procedure was also repeated using beating times of 5, 15, 30 and 45 
minutes. After measuring the solids content, the beaten particles were 
diluted to 3 weight percent suspension. The wet product (solids content 
approximately 3%) was stored in this state. 
EXAMPLE 21 
The cationicity of the various products from Example 20 was measured by 
titrating against standardized 0.001 N sodium polyethylene sulfonic acid 
(Na-PES) using ortho-toluidine blue as an end-point indicator. 
Alternatively, the cationicity was measured by back titration as follows. 
Product obtained by the above methods was mixed with an excess amount of 
standardized 0.001 N sodium polyethylene sulfonic acid (Na-PES) and 
stirred for one hour. The solids were then centrifuged out and an aliquot 
of the clear supernatant titrated against 0.001 N 
polydiallyldimethylammonium chloride (poly-DADMAC) in a particle charge 
detector. The charge of the product was calculated from the consumption of 
poly-DADMAC. 
The cationicity measured by back titration is normally higher than directly 
measured cationicity. This can be explained by the fact that during back 
titration the reagent can penetrate the cellulose structure due to the 
longer duration and thus react with the less accessible charge carriers. 
The following table shows the cationicity of the product from Example 6 as 
a function of different beating times. One can see that the cationicity 
increases with an increase in beating time, which can be explained by the 
fact that longer beating reduces the particle size and thus the specific 
surface area and the available charge. 
______________________________________ 
Beating time in Jokro mill 
Cationic charge (dry product) 
(minutes) (micro-equivalents/gram) 
______________________________________ 
0 251 
5 394 
10 748 
15 911 
30 978 
45 1027 
______________________________________ 
EXAMPLE 22 
The nitrogen content of the dry product from Example 6 was measured using 
the Kjeldahl method. 
The nitrogen content of the dried cationizing agent from Example 6 was 
likewise measured. 
The reference value used for nitrogen content was non-cationized cellulose 
precipitated out in acid as sodium cellulose xanthogenate. However the 
values were below the detection limit of this method. 
By comparing the amount of cationizing agent used and the nitrogen content 
in the finished product one can derive the yield of the reaction. 
Depending on the choice of cationizing agent, it is typically between 60 
and 90%. 
EXAMPLE 23 
The solids content of cationized cellulose made with similar raw materials 
as in Example 6 was measured. Enough of the wet product (solids content 
15%) to give 380 g as dry product was added to the pulper of a Sulzer 
Escher Wyss P 12 laboratory conical refiner. This refiner is normally used 
in the paper laboratory for testing the beating characteristics of fibers 
for papermaking. 
The above amount of cationized cellulose was filled up with water to 12.5 
liters and dispersed for 1 minute. The slurry was then transferred to the 
refiner section of the apparatus, the entrained air was removed and the 
product pumped under continuous circulation through the refiner for 5 
minutes and thus beaten. 
The power setting was kept at 350 watts by an automatic control during 
beating, the speed of the rotor was 1500 rpm. The beating energy for 
processing the cationized cellulose was approximately 0.08 kW/kg. 
The above beating parameters are comparable to those which are used for 
beating fibers for papermaking. 
The beating of the product was also conducted with different times (1, 2, 
3, 4, 6, 7, 8, 9 and 10 minutes). 
After beating, the solids content was measured again, the beaten product 
was diluted to 3% concentration, and stored in this state. 
EXAMPLE 24 
The product from Example 6 was dried in a hot air oven at 105.degree. C. 
until the moisture content was between 4 and 8%. In this form the product 
could easily be broken up into small lumps, the consistency being 
comparable to hard bread, and stored for some time in this state. 
EXAMPLE 25 
The dried product from Example 24 was wetted with water for about 10 
minutes and then beaten in a Jokro mill for 10 minutes as described in 
Example 20. After beating, the solids content was measured again and the 
beaten product diluted to 3% concentration and stored in this state. 
EXAMPLE 26 
The dried product from Example 24 was ground in the dry state in a Braun 
model 4045 coffee mill at the finest setting for 5 minutes and then stored 
in this state. 
EXAMPLE 27 
The cationized cellulose from Example 6 was beaten for 10 minutes using the 
procedure from Example 20. The resultant fine solids particles were 
filtered out of the beaten slurry onto a microfine synthetic filter cloth 
and subsequently dried at 90.degree. C. In this state the product could 
easily be broken up into small lumps, comparable to hard bread, and was 
stored in this state. 
EXAMPLE 28 
The product from Example 20 was spun in a laboratory centrifuge for 5 
minutes at 1000 rpm. The supernatant aqueous phase was decanted off. The 
pasty compound remaining in the tubes had a solids content of 
approximately 18% and was stored in this state. 
EXAMPLE 29 
The product produced in Example 28 was diluted with water to about 3% and 
slowly stirred. The very fine, pasty product could thus be dispersed in 
water again very easily and within a short time. 
EXAMPLE 30 
The product produced in Example 28 was added to a solution of a 
water-soluble cationic polyacrylamide (FLOERGER FO 4190) as is used for 
sludge dewatering. In this case, 50% of the cationized cellulose based on 
the dry weight of cationic polyacrylamide was added. 
The mixture was stirred slowly. The product could thus be dispersed in the 
polyacrylamide solution very easily and within a short time. 
EXAMPLE 31 
The dried product from Example 27 was added to water to give a 
concentration of 3% and stirred for 10 minutes. Then dispersion was 
performed in a high-shear mixer for 5 minutes, resulting in a homogeneous 
suspension. 
EXAMPLE 32 
The product made in Example 20 using a 10 minute beating time was stirred 
slowly to maintain the uniformly dispersed state of the product. The 
stirring was turned off and after one hour the cationized cellulose 
particles were seen to be partially sedimented out. 
After several days a sediment paste formed that constituted about one half 
of the liquid volume. The stirrer was once again switched on whereby this 
sediment could readily redisperse uniformly in the water. 
The thus diluted product, now at approximately 3% solids content, was 
pumped in a circuit using a diaphragm pump (maximum capacity 23 
liters/hour) fitted with ball valves at the suction and delivery sides and 
with suitable pipework of 16 mm internal diameter. After 24 hours of 
continuous circulation there was no reduction of the pumping efficiency. 
Another portion of the dispersed product (also now at 3% solids content) 
was pumped in a circuit using a small, screw-feed or "Mohno" pump (maximum 
capacity 20 liters/hour) fitted with a rubber stator for aqueous media. 
After 24 hours of continuous circulation there was no reduction of the 
pumping efficiency. 
EXAMPLE 33 
Dewatering of Biological Sludge 
Cationized cellulose from Example 20 was used as a 3% dispersion in 
combination with a cationic, water-soluble polyacrylamide-based flocculant 
used in the prior art for dewatering sludge (commercially available as 
Allied Colloids, DP7-5636). This accelerated the dewatering of biological 
sludge and increased the solids content of the dewatered sludge compared 
to use of the cationic polyacrylamide flocculant alone. 
The sludge used in this field test is from a combined municipal/industrial 
sewage works and contains a mixture of primary and biological sludge. This 
sludge was taken from a point between the sludge thickener after the 
anaerobic digester and the final dewatering press, before any 
precipitants/flocculants were added. The solids content was approximately 
2%. 
The standard powdery polymer used in this plant was prepared as an aqueous 
0.3 weight percent solution. This cationic, water-soluble polymer was 
chosen as the most suitable product after a series of optimization trials. 
The cationized cellulose was diluted with water further to a 0.3% solids 
content. This means that any mixture of the two products will always have 
the same concentration of active ingredients. 
The following setup was used for the laboratory tests: 
1) A Britt-jar drainage test apparatus (see enclosed diagram) was fitted 
with a preweighed black ribbon filter (Schleicher & Schull 589, 110 mm 
diameter, ashless). The sieve normally used in the paper laboratory for 
dewatering tests and the precision stirrer were not used. 
2) The drainage tube, equipped with an off/on valve, was connected using 
flexible silicone tubing to a vessel placed on a balance. The balance was 
programmed to send a signal of the registered weight at set time intervals 
to a computer, where it was recorded. This permitted dewatering curves of 
filtrate weight against time to be recorded. The collecting vessel was 
also fitted with a flexible tube to a vacuum pump so that a preset vacuum 
level was adjustable during dewatering. 
3) The precision stirrer supplied with the Britt-jar was installed so that 
the content of a 500 ml beaker could be stirred. 
4) Filter papers (Schleicher & Schull 589, black ribbon, 110 mm diameter), 
dosing syringes, balance, drying oven, etc. 
The following measuring procedure was used. 
A series of flocculant solutions were prepared by mixing 0.3% cationized 
cellulose dispersion with the 0.3% cationic, water-soluble polyacrylamide 
(PAA) flocculant to give a range from straight PAA through various 
mixtures to straight cationized cellulose. The concentration of active 
ingredients was the same in all mixtures. 
500 ml of fresh untreated sludge with 2% solids content was placed in a 
beaker and stirred at 200 rpm for 1 minute. 15 ml of the flocculant was 
then added (45 mg) using a syringe. This simulates the dosage used in 
practice. 
The thus treated sludge was mixed slowly for a further 2 minutes. During 
this time, the vacuum pump was turned on so that the vacuum could 
stabilize. The filter paper in the Britt-jar was moistened and the balance 
zeroed. 
130 ml of flocculated sludge from the beaker was added to the Britt-jar, 
thereby forming a layer of sludge approx. 1.5 cm deep. The valve between 
the Britt-jar and the collecting vessel was opened and the data 
transmission from the balance to the computer started. 
The filtrate weight in the collecting vessel was thus recorded 
automatically during dewatering. When the sludge was fully dewatered, as 
seen by a cessation of liquid coming into the collecting vessel and by air 
being drawn through the sludge into the collecting vessel or, in the case 
of poor dewatering, by the filter being blocked by fine substances, the 
test was stopped. The sludge remaining on the filter was tested for solids 
content. The filtrate was tested for turbidity and for chemical oxygen 
demand (COD). 
The procedure was repeated for various flocculants. The results of filtrate 
weight were plotted against time for each of the flocculants used. The dry 
substance content as well as the filtrate turbidity and COD were also 
tabulated against each flocculant used. 
Results: 
TABLE 1 
______________________________________ 
(Dewatering speed of sludge) 
Dewatering of biological sludge, with various levels of cationized 
cellulose used in combination with polyacrylamide - Filtrate weights 
at various times 
______________________________________ 
Flocculant system for sludge dewatering tests as 
percent of particular component 
% cationized 
0 0 1 2 4 6 8 10 50 100 
cellulose 
% cationic poly- 
0 100 99 98 96 94 92 90 50 0 
acrylamide 
Drainage time 
(minutes) Weight of filtrate over time (g) 
1 5 31 37 48 50 31 32 27 25 8 
2 5 48 50 55 57 46 45 39 30 10 
3 7 54 56 62 67 50 47 44 31 10 
4 8 58 61 69 75 52 51 46 35 15 
5 10 64 67 73 76 55 53 46 37 17 
6 10 67 69 75 80 58 57 53 42 20 
______________________________________ 
TABLE 2 
__________________________________________________________________________ 
(Solids content of dewatered sludge) 
Dewatering of biological sludge, with various levels of cationized 
cellulose 
in combination with polyacrylamide - Solids content of dewatered 
__________________________________________________________________________ 
sludge 
Flocculant system for sludge dewatering tests as percent of 
particular component 
% cationized cellulose 
0 0 1 2 4 6 8 10 50 100 
% cationic polyacrylamide 
0 100 
99 98 96 94 92 90 50 0 
Solids content of dewatered sludge (%) 
* 19.6 
20.8 
22.7 
24.2 
21.9 
21.5 
21.0 
16.1 
* 
__________________________________________________________________________ 
Note. 
Samples marked * could not dewater in a reasonable time since the filter 
was blocked by fine substances. 
TABLE 3 
__________________________________________________________________________ 
(Turbidity and COD of filtrate) 
Dewatering of biological sludge, with various levels of cationized 
cellulose used in 
combination with polyacrylamide - Filtrate turbidity and 
__________________________________________________________________________ 
COD 
Flocculant system for sludge dewatering tests as percent of 
particular component 
% cationized cellulose 
0 
0 
1 
2 4 6 
8 
10 
50 
100 
% cationic polyacrylamide 
0 
100 
99 
98 
96 
94 
92 
90 
50 
0 
Chemical oxygen demand of filtrate (mg O.sub.2 /l) 
COD mg O.sub.2 /l 
1580 
1080 
1060 
980 
970 
1000 
1040 
1050 
1400 
1590 
Turbidity of filtrate (FNU) 
Turbidity FNU 
+450 
405 
400 
388 
364 
393 
402 
415 
+450 
+450 
__________________________________________________________________________ 
The replacement of approximately 4% of the water-soluble cationic 
polyacrylamide by cationized, water-insoluble, beaten cellulose particles 
yielded a surprising and significant increase in the dewatering speed for 
this sludge, together with a marked increase in the solids content of the 
dewatered sludge and a reduction in the turbidity and chemical oxygen 
demand in the filtrate. 
EXAMPLE 34 
Dewatering of Primary Sludge 
The same test procedure as in Example 33 was used for this sludge except 
for the following differences. 
The cationized cellulose used was that made in Example 7 with poly-DADMAC 
as the cationizing agent, the cellulose being beaten for 10 minutes by the 
procedure described in Example 20. 
The sludge used in this example was taken from an industrial, mechanical 
waste-water plant where waste water is normally precipitated, sedimented, 
the sediment concentrated in a sludge thickener and then, after treatment 
with a water-soluble cationic polyacrylamide, dewatered on a band press. 
The standard product used in this plant is known by the trade name FLOEGER 
FO 4190. The sludge used for the laboratory tests was again taken from a 
point between the sludge thickener and the band press, before any 
flocculant was added. The solids content of this sludge was 2%. 
Results: 
TABLE 4 
______________________________________ 
(Filtrate weight during dewatering time) 
Dewatering of biological sludge, with various levels of cationized 
cellulose used in combination with polyacrylamide - Filtrate weights 
at various times 
______________________________________ 
Flocculant system for sludge dewatering tests as 
percent of particular component 
% cationized 
0 0 1 2 4 6 8 10 50 100 
cellulose 
% cationic poly- 
0 100 99 98 96 94 92 90 50 0 
acrylamide 
Drainage time 
(minutes) Weight of filtrate from dewatering of sludge (g) 
0.5 8 21 22 23 25 26 25 21 18 12 
1.0 12 37 40 42 43 44 41 31 24 17 
1.5 14 49 52 55 57 58 52 42 30 19 
2.0 15 54 56 60 64 67 60 49 35 21 
2.5 18 57 58 63 67 72 63 54 40 23 
3.0 20 59 60 66 72 76 69 59 46 24 
______________________________________ 
TABLE 5 
__________________________________________________________________________ 
(Solids content of dewatered sludge) 
Dewatering of biological sludge, with various levels of cationized 
cellulose used in 
combination with polyacrylamide - Solids content of dewatered 
__________________________________________________________________________ 
sludge 
Flocculant system for sludge dewatering tests as percent of 
the particular component 
% cationized cellulose 
0 0 1 2 4 6 8 10 50 100 
% cationic polyacrylamide 
0 100 
99 98 96 94 92 90 50 0 
Solids content of dewatered sludge (%) 
* 32.1 
33.8 
34.4 
37.6 
42.3 
38.5 
35.2 
27.6 
23.1 
__________________________________________________________________________ 
Note. 
The samples marked * could not dewater in a reasonable time since the 
filter was blocked by fine substances. 
TABLE 6 
__________________________________________________________________________ 
(Turbidity and COD of filtrate) 
Dewatering of biological sludge, with various levels of cationized 
cellulose used in 
combination with polyacrylamide - Filtrate turbidity and 
__________________________________________________________________________ 
COD 
Flocculant system for sludge dewatering tests as percent of 
the 
particular component 
% cationized cellulose 
0 
0 1 2 4 6 8 10 
50 
100 
% cationic polyacrylamide 
0 
100 
99 
98 
96 
94 
92 
90 
50 
0 
Chemical oxygen demand of filtrate (mg O.sub.2 /l) 
COD mg O.sub.2 /l 
1250 
890 
880 
810 
740 
790 
870 
880 
1120 
1150 
Turbidity of filtrate (FNU) 
Turbidity FNU 
+450 
320 
308 
285 
252 
267 
312 
338 
401 
449 
__________________________________________________________________________ 
The replacement of approximately 6% of the water-soluble cationic 
polyacrylamide by cationized, water-insoluble, beaten cellulose particles 
yielded a surprising and significant increase in the dewatering speed for 
this sludge, together with a marked increase in the solids content of the 
dewatered sludge and a reduction in the turbidity and chemical oxygen 
demand in the filtrate. 
EXAMPLE 35 
Coagulating Agent in Waste-Water Treatment 
The wash water from a paper coating machine often contains anionically 
charged latex which is a constant problem as a interfering substance when 
this wash water is reused in paper manufacture, as is desirable. It is 
normally required that this wash water be coagulated by neutralization so 
that it can be reused as dilution water on a paper machine or passed into 
the waste-water purification plant. 
The coagulating agents normally used for this purpose are either based on 
water-soluble, highly cationic polymers or solutions of multipositive 
metal ions, or combinations of the two. 
This example demonstrates how the addition of cationized cellulose 
eliminates anionic, colloidal material from the water. Subsequently the 
sedimentation of these ingredients by treatment with conventional 
chemicals is also improved. 
Waste water from a paper coating machine was taken fresh. By titration with 
a .mu.Tek PCD-02 titrator system, the charge, which was highly anionic, 
was measured. The turbidity and the chemical oxygen demand were also very 
high. 
As a control, a sample treated with a standard precipitant (polyaluminum 
chloride ()) was used which was subsequently flocculated with two types 
of a water-soluble, polyacrylamide (anionic+cationic). 
Approximately 10% cationized cellulose, based on the amount of the dry 
weight of polyacrylamide, was added to the waste-water sample and mixed 
for a fixed time. Then the normally used amount of was added, followed 
by the amount of polyacrylamide reduced by the weight of added cationized 
cellulose (=90% of the standard amount). 
The thus treated waste water was poured into a calibrated measuring 
cylinder and allowed to stand for one hour. 
The sludge volume was then measured. A smaller volume indicates a higher, 
and thus more advantageous, sludge density. The turbidity and chemical 
oxygen demand were also measured. As this water would normally be reused 
as process water or alternatively passed into the waste-water purification 
plant, low turbidity and COD are an advantage. 
TABLE 7 
______________________________________ 
(Volume of sediment, turbidity and COD) 
Application of cationized cellulose in coagulation and sedimentation 
of paper coating machine waste water. Analysis of sedimentation in a 
100 ml measuring cylinder. 
Volume of Turbidity of 
COD of 
Coagulation/floccu- 
sediment supernatant 
supernatant 
lation system used 
after 1 hr. ml 
liquid FNU 
liquid mg O.sub.2 /l 
______________________________________ 
none 30 +450 1640 
(poor separation 
of sediment) 
+ PAA 12 44 260 
(cationic) 
+ PAA 14 36 290 
(anionic) 
cat. cellulose + 
10 35 230 
+ PAA (cationic) 
cat. cellulose + 
10 33 220 
+ PAA (anionic) 
______________________________________ 
Surprisingly, the pretreatment of the waste water with cationized cellulose 
clearly improved the sedimentation, turbidity and COD over those levels 
obtained with the standard system. These positive properties were detected 
in combination with both cationic and anionic PAA. 
EXAMPLE 36 
Paper Manufacturing 
Cationized cellulose from Example 6 was beaten for 10 minutes as in Example 
20 and diluted to 3% suspension. This product was used in a laboratory 
test rig for paper retention systems either as a substitute or as an 
additional component, thereby yielding various improvements for the 
papermaking process. 
Retention/Fixation 
A Britt-jar drainage tester was used. 
Part 1) Application in woodfree, fine paper stock 
In the first part of this example, a synthetic paper stock was prepared 
from a mixture of woodfree, beaten, short and long fibers together with 
ground calcium carbonate filler. This thick stock was diluted, salts were 
added to adjust the conductivity, and the pH was adjusted to neutral. The 
stock, when filtered, had a negative charge due to the dissolved or 
colloidally dissolved substances (anionic trash). 
This anionic charge is measured as cationic demand and results from 
titrating an aliquot of the filtrate against a standardized cationic 
polymer (0.001 N polyethylene imine) in a particle charge detector, or 
using suitable color indicators such as ortho-toluidine blue as an 
end-point indicator. 
A series of drainage tests was carried out using various retention systems 
and also replacing individual components of these systems by the 
cationized cellulose explained above. These drainage tests were conducted 
with the Britt-jar stirrer in operation. 
In tests using cationized cellulose as part of the retention system, this 
component was added before the second component, a water-soluble polymer. 
The second component was only added shortly before the start of the 
dewatering phase. 
The Britt-jar filtrate (A) was tested for solids content by being filtered 
through a preweighed, ashless filter paper giving a second filtrate (B). 
The filter paper was ashed to determine the content of filler retention. 
The second filtrate (B) was tested for chemical oxygen demand (COD), for 
turbidity, and for residual anionic charge or cationic demand, as 
described above. 
The results of this test series are shown in Table 8. 
TABLE 8 
______________________________________ 
Effect of cationized cellulose combined with water-soluble polymer on 
total retention, filler retention, etc. Britt-jar test - woodfree, fine 
paper stock, carbonate filler, neutral conditions 
Britt-jar filtrate 
post-filtered Britt-jar filtrate 
total 
filler cationic 
solids 
content turbidity 
CSB demand 
g/l g/l FNU mg O.sub.2 /l 
mg PSK/l 
______________________________________ 
Retention aid system FNU mg O.sub.2 /l 
mg PEI/l 
no retention aid 
2.03 1.14 445 1060 49 
(blank) 
0.6% cationic 
1.71 1.17 294 810 9.6 
polyacrylamide 
0.3% cationic 
1.59 1.22 432 790 18 
polyacrylamide + 
1.0% bentonite 
0.3% cationized 
1.34 0.95 297 770 8.7 
cellulose + 
0.3% cationic 
polyacrylamide 
______________________________________ 
Part 2) Application in a groundwood/deink containing stock 
In the second part of the test series, paper stock was taken as thick stock 
directly from a paper machine mixing chest. This stock contained 
groundwood pulp, deinking pulp, a small amount of pulp fibers together 
with china clay as a filler and was diluted to 1% consistency. 
The same test procedure as above was conducted on this stock. This time a 
water-soluble polyethylene imine was used as a standard retention aid for 
the Britt-jar drainage tests. This polyethylene imine, which is also the 
standard retention aid on the paper machine concerned, was partly replaced 
by cationized cellulose. 
The results of this test series are shown in Table 9. 
TABLE 9 
______________________________________ 
Effect of cationized cellulose combined with water-soluble polymer on 
total retention, filler retention, etc. Britt-jar test - groundwood/ 
deinking/woodfree mixed stock, clay filler, pseudo-neutral conditions. 
Britt-jar filtrate 
post-filtered Britt-jar filtrate 
total 
filler cationic 
solids 
content turbidity 
CSB demand 
g/l g/l FNU mg O.sub.2 /l 
mg PSK/l 
______________________________________ 
retention aid system FNU mg O.sub.2 /l 
mg PEI/l 
no retention aid 
8.8 6.2 237 345 41 
(blank) 
0.6% polyethylene 
7.1 5.3 128 242 25 
imine 
0.3% cationized 
6.6 5.0 94 226 21 
cellulose + 
0.3% polyethylene 
imine 
______________________________________ 
The replacement of some of the water-soluble cationic polymer (either 
polyacrylamide as in Example 1 or polyethylene imine as in Example 2) by 
cationized, water-insoluble, beaten cellulose particles yields a 
surprising and significant increase in the retention of fine substances 
including filler, and reduced turbidity, reduced chemical oxygen demand 
and anionicity and thus a marked decrease in the dissolved and colloidally 
dissolved anionic trash in the second filtrate. These improvements are 
naturally of significant interest to the paper manufacturing process. 
Dewatering 
Part 3) Application in paper stock (woodfree, fine paper) 
In the second series, the Britt-jar was equipped with a larger-diameter 
drainage spout allowing the drainage speed of the stock to be measured 
directly as a function of the stock, the aids added and the sieve used. 
During this modified Britt-jar procedure, the filtrate was collected in a 
vessel placed on an electronic balance. The balance was programmed to send 
a signal of the registered weight at set time intervals to a computer, so 
that dewatering curves of filtrate weight against time could be recorded. 
The results of these tests are shown in Table 10. The retention/dewatering 
system percent refers to dry weight of retention aid on dry weight of 
paper stock. 
TABLE 10 
______________________________________ 
Dewatering of woodfree, carbonate filled, neutral condition paper stock 
measured time 
in sec until definite volumes are reached 
50 ml 
100 ml 150 ml 200 ml 
______________________________________ 
retention/dewatering 
system Dewatering time (seconds) 
no retention system 
47 125 235 312 
0.06% cat. poly- 
13 38 87 141 
acrylamide (PAA) 
0.03% cat. cellulose + 
9 22 52 117 
0.03% cat. PAA 
______________________________________ 
The replacement of some of the water-soluble cationic polymer normally used 
(in this case polyacrylamide) by water-insoluble, cationized, beaten 
cellulose particles yields a surprising and significant increase in the 
dewatering speed for this paper stock. This means that when applied to a 
paper machine, the speed and thus the paper production can be increased. 
EXAMPLE 37 
Cationized cellulose from Examples 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 
17, 18, 19, 25 and 31 was used as a partial replacement of a water-soluble 
polymer retention system in papermaking and the results compared with each 
other. As a control, the polymer alone and a blank were used, and a 
cellulose was also included which was prepared using the procedure of 
Example 7 but without adding any cationizing agent. 
Each product was beaten for 10 minutes by the beating procedure in Example 
20 and used as a 3% slurry. 
The test procedure used was the method of Example 36, Part 1. Each product 
was added in a standard concentration of 0.4% cationized cellulose with 
0.2% water-soluble polyacrylamide as a retention aid system. The paper 
stock was also the same as in Example 36, Part 1. 
The results are shown in Table 11. 
TABLE 11 
______________________________________ 
Britt-jar - comparison of various cationized cellulose products. 
Retention expressed as solids in Britt-jar filtrate 
cationized cellulose product used - 
total solids in Britt-jar filtrate 
example no. g/l 
______________________________________ 
none used (blank) 
4.42 
non-cationized cellulose 
4.35 
100% polymer - no cat. cellulose 
3.01 
6 2.42 
7 2.72 
8 2.66 
9 3.00 
10 3.21 
11 2.56 
12 2.90 
13 2.87 
14 2.58 
15 2.77 
16 2.94 
17 2.80 
19 2.91 
25 2.70 
31 2.87 
______________________________________ 
In this Britt-jar test the retention was always higher with the use of 
cationized cellulose than with the polymer alone. This effect could not be 
detected with the use of non-cationized cellulose. 
EXAMPLE 38 
Paper Properties 
This example demonstrates that by replacing part of conventional retention 
systems by cationized cellulose one can maintain or improve the strength 
of the paper sheet with an increased filler content. This is of interest 
because increased filler content normally reduces paper strength. 
Paper sheets were made using a laboratory sheet former. The stock used was 
basically similar to that used in Example 36, Part 1, that is a mixture of 
woodfree short and long fibers with calcium carbonate filler. 
The cationized cellulose used was that from Example 7, with poly-DADMAC as 
the cationizing agent and 10 minutes of beating as described in Example 
20. 
A range of paper sheets were made using various retention systems and part 
of these retention aids being replaced by cationized cellulose as 
explained above. 
TABLE 12 
______________________________________ 
Properties of paper made on a laboratory sheet former 
Woodfree, carbonate filled stock. Neutral conditions 
Paper gram- 
Filler Porosity 
Breaking 
mage content to air 
length 
Retention system 
g/m.sup.2 % ml/min 
km 
______________________________________ 
None 65.1 2.2 2880 5.9 
0.2% cat. PAA + 1.5% 
66.5 13.1 2710 4.4 
bentonite 
0.6% cat. PAA 67.4 13.9 2850 4.3 
0.4% cat. cellulose 
67.0 15.4 2980 4.4 
(Ex. 7) + 0.2% cat. PAA 
______________________________________ 
EXAMPLE 39 
Fixing Agent for Anionic Trash in Papermaking 
The product from Example 14, beaten for 10 minutes as described in Example 
20, was used to treat a sample of groundwood papermaking fiber stock to 
fix anionic trash. 
This stock, taken as an approximately 4% stock directly from the incoming 
fiber stream for a paper machine, contained relatively high levels of 
anionic trash, such as ligninbased, soluble and colloidally soluble 
substances that interfere with the papermaking process, especially the 
retention system. 
The efficiency of cationized cellulose as a trash catcher was compared with 
inorganic, cationic fixing agents (polyaluminum chloride from Ekokemi) and 
organic, water-soluble cationic polymers (BASF CATIOFAST SL). 
It could also be shown that an overdosing of conventional fixing agents can 
lead to overcationization of the paper machine water circuit, and thus 
also to adverse effects on retention. 
Cationized cellulose was added to 500 ml of the ground-wood stock and mixed 
for 5 minutes. The thus treated ground-wood stock was subsequently 
filtered through a Schleicher & Schull 589 black ribbon filter in a 
vacuum, and the filtrate was tested for turbidity, chemical oxygen demand 
and cationic demand. 
This anionic charge is measured as cationic demand and results from 
titrating an aliquot of the filtrate against standardized cationic polymer 
(0.001 N polyethylene imine) in a particle charge detector or using 
suitable dyes such as ortho-toluidine blue as an end-point indicator. For 
overcationized filtrate, a standardized anionic polymer solution (0.001 N 
Na-PES) was used. 
From these first tests, the cationic demand of the groundwood stock was 
calculated depending on the fixing agent used, and then twice the 
particular amount needed was added. The degree of overcationization of the 
filtrate was measured by titration and is expressed in the table as 
negative cationic demand. 
TABLE 13 
______________________________________ 
Anionic trash fixation in woody paper stock 
Cationic 
Addition on 
Turbidity 
COD in 
demand in 
solids in filtrate 
filtrate 
filtrate 
Fixing agent % dry/dry FNU mg O.sub.2 /l 
mg PSK/l 
______________________________________ 
Blank - none 0 268 328 57.5 
Polyaluminum chloride 
0.3% 220 312 49.7 
() 
- overdosed 
3.5% 262 326 -18.8 
(2.times. neutrality) 
CATIOFAST SL 0.05% 165 302 40.2 
(organic polymer) 
C. SL - overdosed 
0.33% 191 366 -27.5 
(2.times. neutrality) 
Cationized cellulose 
0.1% 171 305 47.9 
Cat. cell. - overdosed 
1.2% 167 278 1.3 
(2.times. neutrality) 
______________________________________ 
The cationized cellulose from Example 14 exhibits a significant ability to 
fix anionic trash compared with conventional fixing agents but has the 
advantage that, due to its water-insoluble nature, it does not lead to 
overcationizing of the filtrate as occurs with the addition of 
water-soluble products. 
EXAMPLE 40 
Dyeing Behavior of Cationic Cellulose Threads 
In a dye bath with a concentration of 5 g/l orange II the inventive 
cationized cellulose of Example 6 or alternatively non-cationized 
cellulose from the xanthogenate process is dyed. Spun threads with 3 dtex 
were used. The bath ratio is 1:6. The dyeing took place at room 
temperature for 30 min. After removal of the spent bath, rewashing with 
desalinated water and drying are performed. 
Measuring results: 
______________________________________ 
Extinction of spent 
Whiteness ISO 
bath 1:100 dil. 
L A B 
______________________________________ 
Blank value 
0.3 
Non-cat. cellulose 
1.732 15.40 71.96 
+38.97 
+42.73 
Cat. cellulose 
0.461 1.38 37.74 
+51.23 
+44.58 
______________________________________ 
Elrepho 2000 for whiteness/color location measurement 
Sample preparation: 
The dried thread is wound as uniformly as possible onto a cardboard strip 
30 mm wide. The winding thickness must be so high that no change of 
measured value takes place through the surface of the cardboard. 
It turns out during the washes of the samples that the fibrous material 
consisting of cationized cellulose has much higher color fastness than the 
non-cationized quality.