F O R M 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
METHOD FOR DEINKING WASTE PAPER

2. APPLICANT(S)
(a) NAME
(b) NATIONALITY
(c) ADDRESS
COATEX
FRENCH Company
35, RUE AMPÈRE,
F-69730 GENAY,
FRANCE
3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL
The following specification describes invention
COMPLETE (√)
The following specification particularly describes the invention
and the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble – “I/We claim”
on separate page)
6. DATE AND SIGNATURE ( to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the separate page)
Note:
*Repeat boxes in case of more than one entry
*To be signed by the applicant(s)or the authorized registered patent agent
*Name of the applicant should be given in full, family name in the beginning
*Complete address of the applicant should be given stating with postal index no. / code, state and country
*Strike out the column which is/are not applicable
This form is digitally signed.
2
Field of the invention
The present invention relates to a method for deinking, decolorizing, disinfecting and
bleaching recycled papers.It also relates to the use of aspecial dispersant in amethod of
deinking comprising at least one flotation step. Thus, the inventionapplies to alldeinking
plants using the method of flotation with dispersed (or circulating) air.
The large-scale recycling of paper and cardboard is nowa reality throughout the world, since
recycled fibers represent about half of the fiber resource needed for global production.
Among the steps of the recycling process, deinking is applied for recycling printed papers,
and aimsto remove the ink from the suspension of recycled paper.
The conventional methods of deinking find application in the treatment of recycled paper
from used paperthat is to be recycled.It is notably a question of treating paper, such as old
newspapers,journals, illustrated magazines, computer listings,continuous forms and
optionallyphotocopies. In the context of the presentapplication, the expression "recycled
paper" means generally all types of paper comprising cellulose fibers, mineral fillers and of
course ink, the latter being present in a tiny amount relative to the mineral fillers and the
fibers. When this waste pulp has been recycled, it only contains a greatly reduced amount of
mineral fillers, for example less than 10% of mineral fillers when initially the dry matter of
the recycled paper contained 28% of said fillers.
Depending on the nature of the paper to be recycled, the proportion of mineral fillers may
thus vary from 5 to 60 wt%, the remainder being cellulose and organic manufacturing
admixtures (latex, starch, antifoaming agents, dyes etc.).
Prior art
The recycled paper is made into a suspension in a device called a "pulper". The latter contains
a medium consisting of water, said recycled paper and at least one deinking agent.It is also
possible to add soda and hydrogenperoxide to the pulper. The whole is stirred/mixed for a
specified time, in order toobtain a pulp, from whichweaim to remove at least the ink in order
toobtainrecycled waste pulp that is ready to be used again, for example in the manufacture of
printing or writingpaper.
3
Removal of the ink from recycled paper is carried out essentially by the method of flotation
with dispersed (or circulating) air. When air bubbles are added to this suspension, which is
the principle of flotation, the ink particles will have a natural tendency to be adsorbed at their
interface.The air bubbles then transport them to the surface, generally forming a foam with a
high concentration of ink.
There are many types of flotationapparatus, which are notably described in documents
EP0 674 040, DE 3524071 or EP 0 305 251.
The flotation step may be repeated several times in succession, for example in different
chambers arranged in line, treating the suspension received from the preceding chamber, in
order toobtain a waste pulp having the desired level of whiteness. The whiteness of paper is
defined by international standard ISO 2470-2:2008, which defines said whiteness with a
value from 0 to 100, the latter value defining an optimal whiteness of pulp.
Each end use of the paper requires a specific whiteness. The more flotation steps the
suspension of waste pulp undergoes, the higher the level of whiteness obtained. However, a
high level of whiteness is obtained at the expense of the recycling yield, i.e. the amount of
recycled waste pulp decreases when we want to obtain a whiter recycled pulp. In other words,
for a given amount mo of paper to be recycled, an amountm1 of recycled waste pulp will be
obtained that is less than the amountm2if the desiredwhiteness for the paper m1 is greater than
the whiteness of the (recycled)waste pulp m2.
The successive flotation steps lead to the gradual removal of the mineral fillers, in addition to
the larger decrease of the ink (and resultant increased whiteness of the recycled waste pulp).
In fact, the inkis bound to the mineral fillers,notably in the case of coated papers,and the
flotation step entrains both the inkand the mineral fillers into the upper phase (classically
present in the form of foam), this phase being extracted in order to remove the ink.
Now, the presence of these mineral fillers at a sufficient level is necessary in all applications
where the paper must have functions or a particular texture, for example a bright appearance,
opacity, a certain density and good printability for various printing processes.
4
At present, because the mineral fillers are largely removed, it is necessary to add said fillers
to the recycled waste pulp again when the latter is intended for such applications. This
represents a considerable additional cost (cost of materials and process for incorporation),
and it would therefore be particularly advantageous, when recycling recycled paper, to be
able to preserve the mineral fillers in sufficientquantity in the recycled waste pulp.
Document WO 96-16223 discloses a method for deinking paper for flexographic printing.
The paper is disintegrated in the presence of an emulsion of particles of a polymer which is a
polymer with a hydrophobic character and therefore is not water-soluble.
DocumentUS 4599190 describes the use of a low-molecular-weight polyelectrolyte
dispersant in methods for secondary deinking of fibers in paper. This method does not
comprise a flotation step.
DocumentWO 2011-030003 relates exclusively to the deinking of inks for inkjet printing by
means of a specific enzyme, which is a laccase. No polyacrylate dispersant is used.
Thus, at present there is no system that is able to remove inks while preserving a sufficient
quantity of the mineral fillers in the waste pulp. The applicant intends to propose asolution
for filling this gap.
Brief description of the invention
In the context of the present invention, it was demonstrated that it is possible, in the flotation
step, to separate the mineral fillers from the ink and, moreover, allow the latter to be carried
preferentially into the upper phase, which is to be extracted. The invention notably involves
the use of a specific dispersant, of the polyacrylate type, used in defined proportions, which
promotes retention of the mineral fillers in the lower phase (which is kept) during flotation,
while allowing the ink to go into the upper phase (which is extracted or removed).
This is particularly advantageous, bearing in mind that a person skilled in the art knows that
the ink and the mineral fillers are bound to one another in the waste pulp.
5
Moreover, the nature of inks is extremely variable,more precisely the different types of ink
have either ahydrophilic nature (water-based inks, for example of the flexo or inkjet type) or
ahydrophobic nature (such as the inks for offset printing and heliogravure or toners).Thus, it
is advantageous for such a dispersant to be capable of separating the inks and the mineral
fillers that are initially bound to one another while being able to keep just the material fillers
in the lower flotation phase (which is kept).
Besides this ability to separate the inks and the mineral fillers in the two separate phases
created during flotation, the present invention also allows a very significant improvement of
the recycling yield (mass of recycled waste pulp, compared to the initial mass of recycled
paper,taking into account alevel of whiteness to be attained).
Thus, the present inventionrelates to amethod for deinking recycled paper,comprising:
- a pulping step consisting of putting said recycled paper into suspension with at least
water to form a pulp, then
- a flotation step consisting of circulating air bubbles in at least one chamber receiving
said pulp, diluted in aqueous solution, so as to form two adjacent phases, the upper
phase containing the ink and intended to be removed,
- a step of introducing at least one deinking agent during the pulping step and/or the
flotation step,
said method further comprising a step of introducing at least one dispersant of the
polyacrylate type, in an amount varying between 0.05 and 3.5 wt% relative to the weight of
the mineral fillers of the recycled paper.
It is to be understood here that the expression "recycled paper" describes all types of paper
comprising cellulose fibers, mineral fillers and inks.
The expression "mineral fillers" means all the inorganic elements that are intended to opacify
the paper (refractive index greater than cellulose), improve the printability and/or lower the
manufacturing costs of the paper (less energy for drying, lower cost of materials), such as
calcium carbonate, titanium oxide,kaolin and/or talc.
6
"Dispersant of the polyacrylate type" means a (meth)acrylic acid polymer having a dispersing
function when it is added to a suspension comprising mineral fillers. The dispersant
according to the present invention is defined more precisely here under.
Other advantageous features of the invention are stated below:
- according to one embodiment, at least one part of said dispersant of the polyacrylate
type is introduced during the pulping step;
- according to one embodiment,more than half of the aforesaid dispersant is introduced
during the so-called flotation step, for example the whole amount of the dispersant is
introduced during said flotation step;
- according to one embodiment, said dispersant of the polyacrylate type has a molecular
weight between 2000 g.mol-1 and 100 000 g.mol-1,preferably between 3000 g.mol-1 and
10 000 g.mol-1, as determined by SEC;
- according to one embodiment, said dispersant is introduced during the pulping step in an
amount varying between 0.25 and 3 wt% relative to the weight of the mineral fillers of
the recycled paper, preferably between 0.8 and 2 wt% relative to the weight of the
mineral fillers of saidpaper;
- according to one embodiment, soda and/or hydrogen peroxide are also added during the
pulping step;
- according to one embodiment, the dispersant of the polyacrylate type is an acrylic acid
homopolymer, optionally in neutralized form.
These various embodiments may be combined with one another.
Moreover, the invention relates to the use of a dispersant of the polyacrylate type in a method
for deinking recycled paper, said dispersant beingintroducedduring the method in an amount
varying between 0.05 and 3.5wt% relative to the weight of the mineral fillers of the recycled
paper.
According to one embodiment, said method for deinking comprises a pulping step, a flotation
step, a step of introducing at least one deinking agent, said dispersant of the polyacrylate type
being introduced during the pulping step.
7
According to one embodiment, said dispersant is introducedduring the method in an amount
varying between 0.25 and 3 wt% relative to the weight of the mineral fillers of the recycled
paper.
Detailed description of the invention
Regarding the deinking agent, this consists of one or more foaming agents known by a person
skilled in the art,for exampleasoap of fatty acid notably of the stearicor oleic type, a fatty acid
or a mixture of fatty acids, anonionic surfactant of the ethoxylated and/or propoxylated fatty
alcohol type, anonionic surfactant of the ethoxylated and/or propoxylated fatty acid type,
various mixtures of surfactants and fattyacids, which may also be combined with enzymes,
modified derivatives of the organosiloxanetype.
Regarding the dispersant used in the context of the invention, it comprises polymers obtained
from acrylic monomers. The acrylic monomer is selected from acrylic acid, methacrylic acid
and mixtures thereof. Thus, the polyacrylatepolymer obtained could be a homopolymer or a
copolymer. It is a water-soluble polymer, not apolymer emulsion.
"Homopolymer or copolymer of (meth)acrylic acid" means either apolymer consisting
exclusively of acrylic acid (acrylic acid homopolymer), or a polymerconsisting exclusively of
methacrylic acid (methacrylic acid homopolymer) or alternatively a polymer consisting of a
mixture of acrylic acid and methacrylic acid (acrylic acid/methacrylic acid copolymer) and
optionally of at least one other monomer unit. In the case of an acrylic acid/methacrylic acid
copolymer, according to one aspect of the invention, the molar ratio of the monomers of
acrylic acid to the monomers of methacrylic acid may vary between 1:100 and 100:1, for
example between1:1 and 100:1 or between 1:1 and 50:1.
Said monomer maybe partially neutralized. Thus, in one embodiment variant, 2 to 50 wt% of
the monomer of (meth)acrylic acid,relativeto the totalweight of the monomer of (meth)acrylic
acid introduced, is neutralized. This may be achieved using a single neutralizing agent or
several neutralizing agents. The monomer may, for example, be partially neutralized using an
alkali-metal or alkaline-earth hydroxide, an alkaline-earth oxide, and/or with an amine. We
may mention,as examples, sodiumhydroxide, potassiumhydroxide, lithiumhydroxide,
calciumhydroxide, magnesiumhydroxide, calciumoxide, potassiumoxide.
8
Moreover, the copolymer according to the invention may also further comprise one or more
otherethylenically unsaturated monomer(s) selected from the group consisting of
2-acrylamido-2-methylpropane sulfonic acid (AMPS), maleic acid, fumaricacid, crotonicacid,
itaconicacid, the unsaturated telomers of acrylicacid, the monomers of formula(I):
(I)
In which:
- Ra,Rb and Rc represent,independently of one another,H orCH3,
- n is an integer varying between 0 and 2 (i.e. 0,1 or2).
Inparticular, the monomermaybe allyl alcohol (n=1), methallylalcohol (n=1), isoprenol(n=2).
Advantageously, isoprenolisused.
"Unsaturated telomers of acrylic acid"means oligomers of acrylicacidor of acryloxypropionic
acid, of formula(II):
wheren is aninteger in the rangefrom1 to 10. These various oligomers maybemixed.
When n = 1, the oligomer is an acrylic acid dimer.
In the presence of other unsaturated monomer(s),according to one aspect of the invention, the
molar ratio of the monomers of (meth)acrylic acid to the otherunsaturated monomer(s) may
vary between 1:1 and 100:1, for examplebetween1:1 and 75:1orbetween1:1 and 50:1.
Other chemical constituents maybe added during the method for deinking, such as soda,
hydrogenperoxide, sodiumsilicate and soap.
Apart from the use of aspecific dispersant, in particular proportions during a step of the
method for deinking, the methodaccording to the invention is known by a person skilled in
the art. More particularly, the recycled paper passes through a pulper, a plurality of purifiers
9
and classifierstations, arranged at different places along the deinking chain, having the
respective function of removing the heavy and large particles, as well asat least one –
conventionally a plurality – flotation cell or chamber. Thus, the method for deinking
according to the invention uses the stations and materials that are usually employed, without
modifying them, but the invention is suitable for the flotation technique and not for the
washing technique.
EXAMPLES
A plurality of tests that have demonstrated the invention relative to the prior art as well as its
various particular features are presented below. For brevity and clarity, only a few results are
presented, but of course the applicant has carried out many other tests and analyses in order
to comprehend and evaluate the context of the invention as defined here.
Compounds used in the tests:
XP 1831(according to the invention):dispersant of the polyacrylate type consisting of 100%
of acrylicacid, with a molecular weight of 4000 g/mol(as determined by SEC),obtained by
conventional methods of radicalpolymerization.
ET1(outside the invention):polymer of the comb type consisting of hanging chains of the
poly(ethylene glycol)type with a molecular weight of about 50 000 g.mol-1
.
ET2(outside the invention):polymer of the comb type consisting of hanging chains of the
poly(ethylene glycol)type with a molecular weight of about 100 000 g.mol-1
.
ET3(outside the invention):Potassium tripolyphosphate(KTPP).
Liptol®
S100:deinking agent consisting of a surfactant of the ethoxylated/propoxylatedfatty
alcohol type marketed by the company CECA.
10
Molecular mass (or molecular weight)Mw of the dispersant of the polyacrylate type
according to the invention:
A technique of this kind employs liquid chromatography apparatus made by WATERSTM
,
equipped with a detector. This detector is a detector of refractometric concentration made by
WATERSTM
.
This liquid chromatography equipment is equipped with a size exclusion column suitably
selected by a person skilled in the art for separating the differentmolecular weights of the
polymers under investigation. The liquidphase forelution is an aqueousphaseadjusted to pH 9
with 1N soda containing 0.05M of NaHCO3,0.1M of NaNO3,0.02M of triethanolamine and
0.03% of NaN3.
In detail, according to a first step, the polymerization solution is diluted at 0.9% dry in the
dissolution solvent for SEC, which corresponds to the liquid phase forelution for SEC, to
which 0.04% of dimethylformamide is added, which performs the role of marker of flow rate
or internal standard. Then it is filtered at 0.2 µm.100 µL are then injected into the
chromatography apparatus (eluent: an aqueousphase adjusted topH 9.00with 1N soda
containing 0.05M of NaHCO3,0.1M of NaNO3,0.02M of triethanolamine and 0.03% of
NaN3).
The liquid chromatography apparatus contains an isocratic pump (WATERSTM 515), the flow
rate of which is set at 0.8 ml/min.The chromatography apparatus also comprises a furnace,
which in its turn comprises the following system of columns in series: aprecolumn of the
GUARD COLUMN ULTRAHYDROGELWATERSTMtype with a length of 6 cm and an
inside diameter of 40 mm, and a linear column of the ULTRAHYDROGELWATERSTMtype
with a length of 30 cm and an inside diameter of 7.8 mm. The detection system consists of a
refractometric detector of the RI WATERSTM 410type. The furnace is heated to a temperature
of 60°C, and the refractometer is heated to a temperature of 45°C.
The chromatography apparatus is calibrated using standards of sodium polyacrylate in
powder form with different molecular weights certified by the supplier: POLYMER
STANDARD SERVICE or AMERICAN POLYMER STANDARDS CORPORATION.
11
The test protocol consisted of adding these products as a supplementin a reference recipe
including a deinking agent and adding the dispersant, either in the pulper
("concentrated"medium at 27% of dry matter in water)or in aflotation cell/chamber ("dilute"
medium at 1% of dry matter in water).
A model HSM10laboratory pulper made by Hobart®
and aDelta®
25 flotation cell/chamber
from the company Voithare used in the context of these tests.
The raw materials considered are identical for all the tests in order to verify that this
parameter (raw materials)does not affect the results.It is a mixture based on newspaper (45%)
and weekly magazines (55%) in order to obtain a mixture with a fairly high level of mineral
fillers, of the order of 28% of the dry matter (the paper contains conventionally 10% of water,
the latter having been removed by drying the aforesaid mixture in aheat chamber).
Similarly, chemical elements, of identical nature and amountfor all the tests, were introduced
in the pulper, namely:
- sodaNaOHat a rate of 6 kg of pure product per tonne of recycled paper,
- sodiumsilicateat a rate of 18 kg of commercial product per tonne of recycled paper,
- hydrogenperoxideat a rate of 7 kg of pure product per tonne of recycled paper,
- Liptol S100 at a rate of 0.5kg of commercial product per tonne of recycled paper.
It should be pointed out that the tests were carried outwithanotherdeinking agent, namely a
mixture of ethoxylated-propoxylated fatty alcohol and fatty acid of the oleic type, and
showed results similarly to those observed with Liptol S100.
Tests carried out:
The method for deinking according to the invention is carried out, testing the various
dispersants mentioned above, introducing them first in the pulping step,and in a secondtest in
the flotation step. For all the tests, it is assumed that a whiteness of the recycled waste pulp of
56 and 59 must be obtained, and for each of these two levels of whiteness we determine the
yield, i.e. the amount of recycled waste pulp (at the desired whiteness) relative to the initial
amount of cellulose fibers present in the recycled paperdry matter (the result is expressed as a
percentage).
12
As a reminder, the dry matter corresponds essentially to the cellulose fibers and the mineral
fillers (as well as the inks), i.e. to the weight of the recycled paperafter removal of the water
and all the other ancillary materials (plastics, staples etc.). The dry matter corresponds to the
portion of the recycled paper that is put in the pulper.
The tests are conducted in the laboratory, using 250 grams of recycled paper each time
(i.e.,assuming 10% of water present, 225 g of dry matter). In order to determine the time
taken, in the flotation step, to obtain the desired level of whiteness (either 56, or 59), a
preliminary analysis is carried out for each test, during which a sample is taken every minute,
and its whiteness is measured. Once the flotation time has been determined for each of the
tests, the test is repeated, leaving the flotation to continue until whiteness of 56 is obtained,
and then a second time until whiteness of 59 is obtained. The yield is then found by
determining the amount of matter recovered (recycled waste pulp)relative to the amount of
dry matter initially present, i.e. of the order of 140 to 160 grams since the yields are of the
order of about 60% to 70%.
In the table given below, the amounts of dispersants are shown as percentage by weight of the
mineral fillers of the recycled paper, asis the traditional practice for dosing the deinking
agent.
Results of the tests carried out on the test specimens with the various formulations:
Besides the tests presented in the following table, complementary tests demonstrated that the
molecular weight of the dispersant according to the invention has an influence on its
effectiveness. Thus, it was demonstrated that the dispersant according to the invention needed
a molecular weight between 2000 g.mol-1 and 100 000 g.mol-1(gram per mole) and preferably
(gain in yield) between 3000 g.mol-1 and 10 000 g.mol-1
.
Moreover, in the method according to the invention, more than 35%, or even more than 40%,
of the mineral fillers present in the recycled paperare preserved in the recycled waste pulp.

13

Tests XP
1831
ET1 ET2 ET3 Yield
(whiteness
56), pulping
step
Yield (56),
flotation step
Yield (59),
pulping step
Yield (59),
flotation step
1 0.05 67.9 65.7 61.8 59.8
2 0.15 70.1 67.8 64.2 62.1
3 0.25 73 70.6 68.3 66.0
4 0.35 75.4 72.90 70.1 67.8
5 0.9 77.3 74.7 71.5 69.1
6 1.1 77.5 74.90 71.6 69.2
7 1.8 77.4 74.8 70.2 67.9
8 2.3 75.9 73.4 69.8 67.5
9 2.9 72.9 70.5 67.9 65.6
10 3.2 69.1 66.8 63 60.9
11 0.9 66.5 63.4 60.2 58.3
12 0.9 66.1 63.3 59.7 57.3
13 0.9 66.2 63.0 60.4 58.0
14 No dispersant 67.6 65.4 61.5 59.5
14
WE CLAIM:
1- A method for deinking recycled paper, comprising:
- a pulping step consisting of putting said recycled paper into suspension with at least
water to form a pulp, then
- a flotation step consisting of circulating air bubbles in at least one chamber receiving
said pulp, diluted in aqueous solution, so as to constitute two adjacent phases, the
upper phase containing ink and intended to be removed,
- a step of introducing at least one deinking agent during the pulping step and/or the
flotation step,
said method further comprising a step of introducing at least one dispersant of the
polyacrylate type, in an amount varying between 0.05 and 3.5 wt% relative to the
weight of the mineral fillers of the recycled paper.
2- The method according to claim 1, wherein at least one part of said dispersant of the
polyacrylate type is introduced during the pulping step.
3- The method according to claims 1 or 2, wherein said dispersant of the polyacrylate
type has a molecular weight between 2000 g.mol-1 and 100 000 g.mol-1, preferably
between 3000 g.mol-1 and 10 000 g.mol-1, as determined by SEC.
4- The method according to any one of the preceding claims, wherein said dispersant is
introduced during the pulping step in an amount varying between 0.25 and 3 wt%
relative to the weight of the mineral fillers of the recycled paper, preferably between
0.8 and 2 wt% relative to the weight of the mineral fillers of said paper.
5- The method according to any one of the preceding claims, wherein soda and/or
hydrogen peroxide are also added during the pulping step.
6- The method according to any one of the preceding claims, wherein the dispersant of
the polyacrylate type is an acrylic acid homopolymer, optionally in neutralized form.
15
7- The use of a dispersant of the polyacrylate type in a method for deinking recycled
paper, said dispersant being introduced during the method in an amount varying
between 0.05 and 3.5 wt% relative to the weight of the mineral fillers of the recycled
paper.
8- The use according to claim 7, wherein said method for deinking comprises a pulping
step, a flotation step, a step of introducing at least one deinking agent, said dispersant
of the polyacrylate type being introduced during the pulping step.
9- The use according to claim 7 or 8, wherein said dispersant is introduced during the
method in an amount varying between 0.25 and 3 wt% relative to the weight of the
mineral fillers of the recycled paper.