Method and adjuvant composition to improve retention of particles on a wire screen

Disclosed is a method for the production of paper and an adjuvant composition comprising the following ingredients: 30 to 80% by weight of phenolic resin or modified phenolic resin; 10 to 50% by weight of melamine resin; and 5 to 35% by weight of at least one naphthalene sulphonate salt. The ingredients are under granulated form or dissolved in an aqueous solution. The method comprises the step of admixing the adjuvant composition with a solution of one or several polyethylene oxide having a molecular weight varying from 1.times.10.sup.6 to 13.times.10.sup.6 and with an aqueous mixture comprising lignocellulosic particles and an aqueous medium to significantly improve the retention of particles such as fines and fibers, on a wire screen and the drainage of the aqueous medium.

The present invention relates to a method for the production of paper and 
to an adjuvant composition which significantly improves the retention of 
particles such as fines and fibers, on a wire screen and the drainage of 
the aqueous medium. 
Advantageously, a particles retention, especially a retention of fines and 
fibers can be achieved for kraft, sulphite (high yield and low yield), 
bisulphite, mechanical, OPCO, BTCMP, TCMP, BCMP, hard wood, such as oak, 
birch, maple, elm, wild-cherry, soft woods such as conifer trees, and TMP 
pulps and any mix in any proportion of two or more types of pulp. 
Applications may be the followings: 
any washer, thickener, save-all, disc filter or drum filter in any pulp 
making process; 
any pulp machine, board machine or paper machine in the production sector; 
any clarifier or flotation or fiber separation unit in the effluent 
treatment process, including krofta, posseidon, sedimentation clarifier, 
but not limited to these; 
any equipment used in the de-inking process, included or not above. 
The Applicant already disclosed in International Patent Application 
publised under no. WO 94/11575 on May 26, 1994 to use a mixture of one or 
more polyethylene oxides with naphthalene sulphonate salts, as an 
adjuvant, to improve the retention of fines and fibers on a wire screen 
from a mixture comprising lignocellulosic fines and fibers and an aqueous 
medium, and thereby to improve the drainage of the aqueous medium. 
The Applicant has now improved the method disclosed in PCT application 
number WO 94/11575 to reduce the amount of naphthalene sulphonate salts 
used in the production of paper. 
The Applicant found has a new and improved method involving a combined use 
of an new adjuvant composition with a solution of one or several 
polyethylene oxide having a molecular weight varying from 1.times.10.sup.6 
to 13.times.10.sup.6, in a mixture of lignocellulosic particles and an 
aqueous medium, which allows to further improve the retention of the 
particles on a wire screen and the drainage of the aqueous medium. 
More particularly, the invention relates to an improvement in a method for 
the production of paper and analogous products. This improvement is 
characterized by the fact that a retention and drainage aid composition 
hereinafter called adjuvant composition comprising following ingredients: 
30 to 80% by weight of phenolic resin or modified phenolic resin; 
10 to 50% by weight of melamine resin; and 
5 to 35% by weight of at least one naphthalene sulphonate salt, 
and a solution of one or several polyethylene oxide having a molecular 
weight varying from 1.times.10.sup.6 to 13.times.10.sup.6, are admixed 
with an aqueous mixture comprising lignocellulosic particles, such as 
fibers and fines, and an aqueous medium. The ingredients of the adjuvant 
composition are either under granulated form or dissolved in an aqueous 
solution. The polyethylene oxide is admixed with the aqueous mixture when 
this latter already contains at least a part of the adjuvant composition. 
The invention also relates to the adjuvant composition as defined above and 
to the use of said composition to improve the drainage. 
Preferably, the adjuvant composition comprises modified phenolic resin 
instead of phenolic resin. A modified phenolic resin is preferred to a 
non-modified phenolic resin since it is of lower lowered toxicity. 
Furthermore, the modified phenolic resin has a longer shelf life varying 
around 18-24 months instead of a few months for the non-modified phenolic 
resin. Among the modified phenolic resin suitable for embodying the 
adjuvant composition of the present invention, products sold under the 
commercial names CASTOPHEN PR-511, Liquid TRICORESERVE NSB, INTERATEX N-8 
150%, CENEKOL 1141, CENEGEN B conc, CENEKOL FT Supra, CENEGEN and CENEKON 
NCS Liquid are preferred. 
Advantageously, the adjuvant composition further comprises up to 10% by 
weight of at least one alkoxylated alkyl phenol, and preferably an 
ethoxylated nonyl phenol. 
Preferably, the adjuvant composition is in association with an aqueous 
excipient and the polyethylene oxide is in association with an aqueous 
excipient, both aqueous excipients being the same or different. Both 
associations may be admixed with a mixture comprising lignocellulosic 
fines and fibers to thus define either a pulpable pulp or an aqueous 
suspension. 
Advantageously, the adjuvant composition comprising the naphthalene 
sulphonate salt(s), especially sodium naphthalene sulphonate salt, is 
uniformly dispersed in the mixture before introducing one or several 
polyethylene oxide. Preferably, the adjuvant composition should be applied 
at least 30 seconds before it gets in contact with the polyethylene oxide 
to thus give enough time to the salts of the adjuvant composition to 
condition the particles, such as fines and fibers. 
Advantageously, the aqueous suspension is either of the type intended to be 
laid on a wire screen of a paper machine to form a sheet of paper or of a 
pulp machine, or of the type defining a white water collected in a wire 
pit of a paper machine of a pulp machine. This white water may be 
partially or totally recycled as an effluent of a step for preparing a 
pulpable pulp comprising lignocellulosic fines and fibers and an aqueous 
medium, or passed at least in part with other waste water through a 
clarifier. This white water charged with the adjuvant composition and 
polyethylene oxide contributes to make the clarifier more efficient. 
Preferably, in a pulp and paper plant, the admixture of the adjuvant 
composition with the mixture of lignocellulosic fines and fibers and 
aqueous medium may be applied anywhere in the system and advantageously 
not between fan pumps and a head box. It may be applied in the white water 
system (wire pit), mixing tank, in the preparation of clay system or any 
tank that could be in contact with fiber giving on the machine. 
Preferably, the admixture of the adjuvant composition with the mixture of 
lignocellulosic fines and fibers and aqueous medium is applied in the 
mixed pulp tank. The polyethylene oxide solution may be applied preferably 
between the fan pumps and the head box, but it is also possible to apply 
it before the fan pumps and remain efficient, like between the mix tank 
and the fan pumps. 
In use, the aqueous suspension is laid on a wire screen of a paper machine 
to form a sheet of paper fed in pulp machine type. The water collected in 
the wire pit of the paper machine or of the pulp machine and essentially 
consisting of a part of the aqueous suspension not retained on the wire 
screen and still containing the ingredients of the adjuvant composition 
and polyethylene oxide, is recycled for preparing either a pumpable pulp 
or a fresh aqueous suspension intended to be laid on the wire screen, 
being understood that the recycled white water contributes for a part to 
the admixture of the adjuvant composition and polyethylene oxide with the 
aqueous suspension. 
Preferably, an equilibrium is set between the amount of the ingredients of 
the adjuvant composition and polyethylene oxide retained on the wire 
screen and the amount of the ingredients of the adjuvant composition and 
polyethylene oxide collected in the white water in the wire pit and 
recycled to the preparation of either a pumpable pulp or a fresh aqueous 
suspension intended to be laid on the wire screen, to thus allow to admix 
to the pulp or fresh aqueous suspension intended to be laid on the wire 
screen, only the amount of the ingredients of the adjuvant composition and 
polyethylene oxide retained in the sheet of paper or in the pulp. 
Advantageously, the naphthalene sulphonate salt(s) comprised in the 
adjuvant composition are selected from the group consisting of sodium, 
potassium, ammonium, calcium and aluminium salt(s). 
Advantageously also, the polyethylene oxide has a molecular weight varying 
from 4,5.times.10.sup.6 to 12.times.10.sup.6. 
At least one enhancer may further be admixed to the mixture. This at least 
one enhancer is selected from the group consisting of polyaluminium 
sulphate, polyaluminium silicate sulphate, sodium aluminate, polyaluminium 
chloride, magnesium hydroxide and bentonite. 
Advantageously, the polyethylene oxide may be admixed with the aqueous 
mixture of lignocellulosic particles, such as fines and fibers, to 
represent from 10 to 1500 grams per ton of dry matter of the mixture, 
preferably from 30 to 600 grams per ton of dry matter of the mixture. 
Advantageously also, the ingredients of the adjuvant composition may be 
admixed with the aqueous mixture of lignocellulosic particles, such as 
fines and fibers, to represent from 50 to 1500 grams per ton of dry matter 
of the mixture, preferably from 50 to 500 grams per ton of dry matter of 
the mixture.

EXAMPLE 
A BRITT GAR test, well known in the industry, was performed on the three 
different compositions to test their efficiency to improve the retention 
of particles on the wire screen and the drainage of the aqueous medium. 
The first composition, referred to as INTERAC 1323, comprised the adjuvant 
of the present invention. More precisely, the adjuvant composition 
comprised: 
50% of phenolformaldehyde resin (sold under the trade name of CASCOPHEN 
PR-511 by BORDEN); 
30% of sulfonated melamine formaldehyde resin (sold under the trade name of 
MELADYNE by HANDY CHEMICALS); and 
20% sodium naphthalene sulphonate (sold by HANDY CHEMICALS). 
The second composition, referred to as INTERAC 1169, was the composition of 
the closest prior art, viz. the composition of the Applicant's own PCT 
application published May 26, 1994 under the publication number WO 
94/11575. More particularly, INTERAC 1169 comprises 100% of sodium 
naphthalene sulphonate (sold by HANDY CHEMICALS). 
The third composition comprised 100% of phenolformaldehyde resin (sold 
under the trade name of CASCOPHEN PR-511 by BORDEN). 
To each composition, 60 grams per ton of dry matter of a mix polyethylene 
oxide having a mean molecular weight ranging between 7 to 8.times.10.sup.6 
was added. 
Finally, to each composition, an aqueous mixture of lignocellulosic 
particles was admixed in such an amount that each composition represent 
either 564, 1128 or 1692 grams per ton of dry matter of the mixture. 
The resulting compositions were alternatively tested. For 20 each 
composition, the percentages of the First Pass Retention (%FPR), the First 
Pass Ash Retention (%F) and the drainage in milliliter of said 
composition has been mesured. The results concerning INTERAC 1323, INTERAC 
1169 and the third composition are reported in table 1, 2 and 3 
respectively. 
TABLE 1 
______________________________________ 
results of tests performed on INTERAC 1323 
First pass First pass ash 
Dosage retention retention Drainage 
g/T FPR % F % (ml) 
______________________________________ 
564 67.9 53.7 194 
1128 71.4 61.3 198 
1692 76.1 63.7 206 
______________________________________ 
TABLE 2 
______________________________________ 
results of tests performed on INTERAC 1169 
First pass First pass ash 
Dosage retention retention Drainage 
g/T FPR % F % (ml) 
______________________________________ 
564 32.8 31.1 190 
1128 39.7 33.4 194 
1692 41.2 37.9 192 
______________________________________ 
TABLE 3 
______________________________________ 
results of tests performed on the third composition 
First pass First pass ash 
Dosage retention retention Drainage 
g/T FPR % F % (ml) 
______________________________________ 
564 53.7 40.6 196.0 
1128 62.0 48.1 193.5 
1692 63.9 55.9 186.9 
______________________________________ 
Generally, the higher the values of %FPR and %F are, the more fibers are 
retained on the wire screen and the more efficient is the composition. 
Furthermore, more the %FPR and the %F values are and lesser the 
drainage values tends to be. However, higher is the drainage and shorter 
is the drying of the paper and the best dynamic properties the paper has. 
Consequently, one must find an optimal dosage range to obtain the best 
possible %FPR and still achieving a good drainage. 
The values of the tables 1, 2 and 3 have been normalized with a control to 
be suitable for comparison to each other. The control comprises 
lignocellulosic fibers only. The results obtained for the calibration with 
the control are listed in table 4. 
TABLE 4 
______________________________________ 
results of the calibration with the control 
First pass First pass ash 
Dosage retention retention Drainage 
g/T FPR % F % (ml) 
______________________________________ 
0 30.1 29.2 187 
______________________________________ 
According the results listed in the tables 1 to 4, it is possible to deduce 
the relative improvment of each composition by dividing the results of 
each composition by the results of the control. These results showing the 
relative improvment are listed in table 5. 
TABLE 5 
______________________________________ 
relative improvment of the three different compositions 
First pass 
First pass 
ash 
retention 
retention 
Dosage FPR % F % Drainage 
composition 
g/T (%) (%) (%) 
______________________________________ 
INTERAC 1323 
564 125.6 83.9 3.7 
1128 137.2 109.9 5.9 
1692 152.8 118.2 10.2 
INTERAC 1169 
564 9.0 6.5 1.6 
1128 31.9 14.4 3.7 
1692 36.9 29.8 2.7 
third 564 78.4 39.0 4.8 
composition 
1128 106. 64.7 3.5 
1692 112.3 91.4 0.0 
______________________________________ 
As apparent from table 5, INTERAC 1323, which is the adjuvant of the 
present invention, is significantly better than INTERAC 1169 or the third 
composition. The increase in the %FPR is higher for INTERAC 1323 than for 
any other composition. Furthermore, the superiority of INTERAC 1323 is 
clearly marked by the increase of the %F. Finally, the improvement in 
the drainage is as good or even better than the third composition or 
INTERAC 1169. 
In fact, according to table 5, the third composition seems better than 
INTERAC 1169, but not as good as INTERAC 1323. However, the third 
composition consisting of phenolic resin only would be to expensive to 
used. The composition has been illustrated herein for the comparison 
purpose only since, in the industry, this composition is not often used 
because it would be too expensive to use it. 
Accordingly, the present invention provides an adjuvant composition that is 
better and cheaper to produce and to use and comprising less hazardous 
compound such as the phenolic resin which is toxic, than the other 
composition. 
Although preferred embodiments of the invention has been described in 
detail in the specification and in the example, it is to be understood 
that the invention is not limited to these precise embodiments and that 
many changes and modifications may be effected therein without departing 
from the scope or spirit of the invention.