Note: Descriptions are shown in the official language in which they were submitted.
WO95/04187 ~ 1 6 8 ~ 7 8 PCT~S94/08774
IMPROVED DEINKING METHOD USING INK AGGLOMERATION
Field of Invention
This invention generally relates to an improved
agglomeration process to deink printed paper. More
particularly, it concerns a process which provides more
effective agglomeration of ink particles by separating
the defibering and agglomeration steps which are subject
to different chemical and physical requirements.
Agglomerated ink particles are removed by size and
density separation procedures to produce an ink free pulp
medium used to make recycled paper and board products.
Backqround Art
In the past paper was printed with primarily water
or oil based inks which were satisfactorily removed by
conventional deinking procedures. In conventional
deinking procedures, the paper is mechanically pulped and
contacted with an aqueous medium containing a deinking
chemical. The pulping and presence of the deinking
chemical results in a separation of the ink from the pulp
fibers and the dispersed ink is then separated from the
pulp fibers by washing or flotation processes.
Today, increasing amounts of printed paper are
generated from electrophotographic processes such as
xerography and non-impact printing processes such as
laser and ink-jet printing. Deinking processes capable
of deinking these types of printed paper are very complex
and are capital intensive. In addition, multiple steps
are required for debris removal and actual ink removal.
Generally, ink removal procedures involve washing,
flotation, forward cleaning and high consistency
dispersion to reach the level of speck removal and
brightness required in the deinked pulp to produce
recycled paper.
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--2--
U.S. Patent No. 4,561,933 to Wood, discloses a
process for deinking xerographically printed wastepaper.
Repulped printed wastepaper is treated with a deinking
agent consisting of a mixture of alkanols and alcohol
ethoxylates to produce a suspension of ink particles.
The suspended ink particles are separated from the
resulting pulp-medium by washing and flotation process
steps. The deinking chemical and process in Wood,
however, is limited to deinking only xerographic waste
and utilizes multiple process steps to separate the ink.
To surmount these limitations, and as an alternative
to conventional deinking procedures, the prior art has
shown use of agglomeration deinking processes.
Agglomeration chemicals consisting of polymeric or
surfactant systems are employed to aid in the ink
agglomeration process. In deinking paper through
agglomeration processes the waste paper is repulped and
then deinked through chemical treatment to provide a
slurry of pulp and ink agglomerates. The ink
agglomerates are removed from the pulp by sedimentation
and separation procedures.
However, the polymeric systems used in these
agglomeration process~C are specific to certain types of
inks. See U.S. Patent No. 4,820,379 to Darlington, in
which the deinking chemical used is specific for
agglomeration of electrostatic inks, and U.S. Patent No.
4,076,578 to Puddington et al. in which the deinking
chemical used is specific for agglomeration of newspaper
inks. Alternatively, U.S. Patent Nos. 5,141,598 and
5,200,034 to Richmann et al. discusses surfactant systems
including alcohol, glycol and petroleum distillate
components, specific for agglomerating electrostatic
inks.
These patents disclose agglomeration processes in
which the repulping and agglomeration actions are carried
W095/04187 21~6 8 ~ 7 8 PCT~S94/o8774
out in the hydrapulper or similar device under the same
conditions. There is no distinction made as to the
different chemical and physical requirements for the
defibering and agglomeration actions. A major constraint
in simultaneous repulping and agglomeration is that the
action of the hydrapulper breaks the ink int-o smaller
particles at the same time that agglomeration is forming
larger particles. By separating the repulping and
agglomeration steps agglomeration will proceed without
any particle breakdown thereby producing larger
agglomerates which are easier to remove from the pulp.
Therefore, known deinking processes are not entirely
satisfactory in that the chemicals used are selective as
to the type of ink. Also high concentrations of
expensive chemicals are necessary to obtain effective
deinking results and adequate pulp cleanliness is not
necessarily achieved. Such process~s are cost
inefficient as well. Thus the present practice,
employing known deinking processes and agglomeration
chemicals have limitations to specific inks and require
complex and expensive procedures to obtain recycled grade
paper.
There is a need in the art for deinking processes
which are less complex and cause agglomeration of all
types of inks, both impact and nonimpact, for all grades
of paper. This invention is directed to the provision of
such processes which have a wide range of applications in
creating recycled grade paper. It would be appreciated
that advantage over conventional deinking procedures
would be obtained by providing an effective and efficient
deinking method applicable to all types of printed paper.
Accordingly, it is a broad object of the invention
to provide an improved deinking process producing more
effective agglomeration of ink particlçs through
separation of the defibering and agglomeration steps
WO95/04187 PCT~S94/08774
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-4-
which are subject to different chemical and physical
requirements.
A more specific object of the invention is to
provide a deinking process and related apparatus which
utilizes a two-component deinking chemical, including
alkanol and nonionic surfactant based systems, for the
agglomeration of all types of inks, both impact and
nonimpact, from wood containing and wood free grades of
paper, in which the components are added separately
during the deinking process to improve agglomeration of
ink particles.
Another object of the invention is to provide a low
cost agglomeration deinking process that effectively and
efficiently removes ink without using a high
concentration of expensive agglomeration chemicals.
A further specific object of the invention is to
provide an agglomeration deinking method which is less
complex than the prior art ink removal procedures.
Another object of the invention is to provide a
recycled paper product having a high level of cleanliness
made by the agglomeration deinking method of the
invention from printed wastepaper.
A further specific object of the invention is to
increase the pulp brightness by recirculating the
substantially ink free pulp medium and reject streams to
cause additional agglomeration of ink particles, wherein
removal of the reagglomerated ink particles produces a
cleaner pulp medium.
Disclosure of Invention
In the present invention, these purposes, as well as
others which will be apparent, are achieved generally by
providing an improved agglomeration process for deinking
printed paper by separating the defibering and
agglomeration steps which are subject to different
WO95/04187 PCT~S94/08774
5 7 8
chemical and physical requirements. Size and density
separation procedures are employed to remove agglomerated
ink particles and produce an ink free pulp medium for use
in the fabrication of recycled paper and board products.
The general deinking process comprises the steps of
defibering the printed paper to produce a pulp medium and
contacting with an aqueous medium containing an
agglomeration deinking chemical. The presence of the
deinking chemical causes agglomeration of ink particles
to produce an ink pulp medium. The defibering and
agglomeration are done separately in a defibering device
and mixing vessel, respectively. The ink pulp medium is
passed through a pressure screen and/or a centrifugal
cleaner to remove ink particles and to produce a
substantially ink free pulp medium. The substantially
ink free pulp medium is thickened and then made into a
recycled paper product through conventional papermaking
processes.
In an alternate embodiment of the process of the
invention the substantially ink free pulp medium is
recirculated to the mixing vessel to cause additional
agglomeration of ink particles. After reagglomeration,
the agglomerated ink particles are removed to produce a
cleaner pulp medium. Additionally, reject streams from
the production of the substantially ink free pulp medium
are recirculated to the mixing vessel to again cause
additional agglomeration of ink particles. After
reagglomeration, the agglomerated ink particles are
removed to increase pulp medium yield and ink removal
efficiency.
The pulp medium may be subjected to screening and
cleaning procedures to remove contaminants, such as
staples, glass, paper clips, plastic and stickies prior
to agglomeration in the mixing vessel.
The deinking chemicals used in the invention are
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--6--
generally a blend of chemicals having at least two
different component functionalities. The first
component, referred to as chemical A, acts to remove ink
from fiber, lower the glass transition temperature of
polymeric inks and to wet the ink particles. The second
component, referred to as chemical B, is a
coalescing/liquid bridging agent. The process of the
invention utilizes a single deinking agent containing the
combined components and functionalities of deinking
chemicals A and B. Alternatively, deinking chemical A
and deinking chemical B are added as separate components
at different points in the invention process. The net
effect is to split up the chemical actions of the
deinking agent to permit higher concentrations of active
agents at the unit operations where they are most
effective. Deinking chemical A is typically a nonionic
surfactant of the ethoxylate type, whereas deinking
chemical B is an alkanol which functions as a coalescing
and/or liquid bridging agent.
Process and reaction conditions are controlled in
the defibering device and mixing vessel so that effective
agglomeration of the ink particles is accomplished.
Concentrations of the deinking chemical, as well as the
pH and temperature of the aqueous medium are adjusted to
yield maximum agglomeration of the ink particles. Coarse
and fine ink particles are removed from the ink pulp
medium by size and density separation procedures. The
resulting ink free pulp medium has a speck removal and
brightness level sufficient to produce high-grade
recycled paper.
Preferred applications of the method of the
invention include use in deinking printed paper to
produce high-grade recycled printing and writing paper,
or other products such as tissue and towelling, bag
grades or board products. Advantageously, the deinking
WO95/04187 2 l 6 ~ ~ ~ 8 PCT~Sg4/08774
method of the invention provides agglomeration processes
that are less complex and ~Yp~cive and more efficient
than known agglomeration processes.
The invention also provides an apparatus for
deinking printed paper utilizing a repulping means, an
agglomeration means, a separation means for coarse ink
and fine ink and a production means to produce recycled
paper.
Other objects, features and advantages of the
present invention will be apparent when the detailed
description of the preferred embodiments of the invention
are considered in conjunction with the drawings, which
should be construed in an illustrative and not limiting
sense as follows:
Brief Descri~tion of the Drawings
FIG. lA is a diagrammatic view of the general
process steps of the invention for deinking of printed
paper;
FIG. lB is a diagrammatic view of another embodiment
of the general process steps of the invention for
deinking of printed paper;
FIG. 2 is a schematic view of an apparatus for
deinking of printed paper in accordance with the process
of the present invention; and
FIG. 3 is a schematic view of an apparatus for
deinking of printed paper in accordance with another
embodiment of the process of the invention.
DETAILED DESCRIPTION OF THE ~KKED EMBODIMENT
The present application is specifically directed to
a deinking process which provides more effective
agglomeration of ink particles by separating the
defibering and agglomeration steps. Effective
agglomeration of ink particles is achieved by splitting
WO95/04187 PCT~S94/08774
21 ~8~78
the defibering and agglomeration actions which are
subject to different chemical and physical requirements.
Agglomerated ink particles are removed by size and
density separation procedures to produce an ink free pulp
medium used to make recycled paper and board products.
Copending U.S. Patent Application No. 07/771,370
filed October 3, 1991 discloses use of an agglomeration
tower to separate the repulping and agglomeration steps.
Specific deinking chemicals used in the present invention
are disclosed in copen~;~g U.S. Patent Application Nos.
07/984,784 filed December 3, 1992 and 08/093,443 filed
July 16, 1993, both applications are a continuation-in-
part and a continuation, respectively, of U.S. Patent
Application No. 07/720,336 filed June 25, 1991, now
abandoned. The copending application specifications are
incorporated herein by reference.
With further reference to the drawings, FIG. lA and
lB are diagrammatic views of the general process steps
for the deinking of printed paper.
Defibering of the printed paper occurs in a
defibering device to produce a pulp medium 1. After
defibering the pulp medium is p~ce~ to a mixing vessel
containing a deinking chemical 2. The presence of the
deinking chemical causes agglomeration of ink particles
to produce an ink pulp medium. The resulting ink pulp
medium is passed through one or more steps of screening
3 or centrifugal cleaning 4, to remove large ink
particles and contaminants and to produce a substantially
ink free pulp medium 6.
As shown in FIG. lB, prior to reaching the mixing
vessel 2 the repulped fibers may be subjected to
screening and cleaning procedures lA to remove
contaminants, such as staples, glass, paper clips,
plastic and stickies prior to agglomeration.
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In an alternate embodiment of the process of the
invention, the substantially ink free pulp medium is
recirculated to the mixing vessel 2 to cause additional
agglomeration of ink particles, wherein reagglomerated
ink particles are removed to produce a cleaner pulp
medium. Additionally, reject streams from the production
of the substantially ink free pulp medium are
recirculated to the mixing vessel 2 to cause additional
agglomeration of ink particles, wherein reagglomerated
ink particles are removed to increase pulp medium yield.
In any of the embodiments the substantially ink free
pulp medium can then be made into a recycled paper
product through conventional papermaking t~chni ques.
The critical aspect of the present invention process
is in the separation of the defibering and agglomeration
steps. The mechAn;cal and chemical actions required for
the defibering and agglomeration steps are different.
The key differences are summarized in Table I below.
TABLE I
CONPARI80N OF D~r~ TNG AND AGG~OM~R~TION ACTION8
MRC~t'ICA~/PHY8ICAL REQU~:r~:r
D~rl~KING AGGT~M~TION
High attrition/shear Low attrition/shear
Moderate mixing Very good mixing
Batch/continuous Batch/semi-continuous
CHEMICAL REQUT~M~NT8
rl~r~ING ~"~T OMERATION
Any pH Preferably pH 7 to 11
Wetting agents Coalescing and/or
(optional) liquid bridging agent
Low temperature Normally elevated
temperature
SUB~TITUTE SHEET (RULE 26~
WO95/04187 PCT~S94/08774
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--10--
Generally, the defibering step is carried out in a
high shear device such as a hydrapulper. Other devices
providing similar action can also be employed. The
defibering step is carried out -preferably at low
temperature in the range of 25 to 45-C with or without
alkali to cause separation of the paper fibers.
Preferably defibering is carried out for lO to 20
minutes.
For effective agglomeration to occur, low shear
mixing is preferred which may be achieved in a mixing
vessel which is a device other than a pulper. A pulper
is generally used for the defibering step and not the
agglomeration step. Processes in which the repulping and
agglomeration actions are carried out in a hydrapulper or
a similar device result in the hydrapulper breaking the
ink into smaller particles at the same time that the
agglomeration action is forming larger particles. By
separating the repulping and agglomeration steps
agglomeration will proceed without any particle breakdown
thereby producing larger agglomerates which are easier to
remove from the pulp. This increases the utilization of
pulper capacity, which can be a serious limitation in
some commercial operations. The invention process
therefore provides for increased production through
better pulper utilization and increased yield of clean
pulp .
In addition to agglomeration the mixing vessel can
also be used for bleaching the pulp since temperature and
pulp consistency conditions are suitable. Multiple stage
bleaching could be accomplished in the vessel because of
its design for continuous gentle agitation.
After defibering, the pulp medium is passed to the
mixing vessel where the deinking chemicals are added.
Agglomeration deinking chemicals used in the
invention are a blend of chemicals having at least two
WO95/04187 PCT~S94/08774
216~78
different component functionalities. The first
component, referred to as chemical A, acts to remove ink
from fiber, lower the glass transition temperature of
polymeric inks and to wet the ink particles. The second
component, referred to as chemical B, is a
coalescing/liquid bridging agent. The process of the
invention utilizes a single de;nk;ng agent cont~;n;ng the
combined components and functionalities of deinking
chemicals A and B. Alternatively, deinking chemical A
and deinking chemical B are added as separate components
at different points in the invention process. The net
effect is to split up the chemical actions of the
deinking agent to permit higher concentrations of active
agents at the unit operations where they are most
effective.
Typically, Chemical A, which removes ink from the
paper fiber and reduces the glass transition temperature
of inks, is preferably an ethoxylated nonionic
surfactant, but any other nonionic surfactant may be
used. Chemical B is an alkanol, preferably a mixture of
C5 to C20 alkanols, but any liquid bridging or coalescing
agent for ink may be used.
Any deinking agent as known in the art can be used
in the process of the invention. Many types of deinking
agents which may be used have been proposed in copen~;ng
U.S. Patent Application Nos. 08/093,443 and 07/984,784.
These applications disclose deinking compositions
including a mixture of C5 to C20 alkanols and nonionic
surfactants. Alkanols with a carbon number range from 8
to 16 having a straight chain or a slightly branched
structure are most preferred. Alternatively, secondary
or tertiary alcohols or any chemical agent capable of
strong hydrogen bonding and forming liquid bridges
between ink particles causing them to agglomerate, are
used in the invention.
WO95/04187 PCT~S94/08774
21~5~
The prior applications also disclose a wide variety
of nonionic surfactants which may be used in the
invention including polyakyleneoxy ether,
polyoxyalkylether, polyoxyethylenephenol ether,
oxyethylene-oxypropylene block copolymer,
polyoxyethylenealkylamine, sorbitan fatty acid ester,
polyoxyethylenesorbitan fatty acid ester, polyethylene
glycol esters and diesters and any other nonionic surface
active agents with wetting power to reduce the surface
tension of water molecules. Particularly preferred
nonionic surfactants are of the polyakyleneoxy ether type
or ethoxylate derivatives of the C5 to Cz0 alkanols,
having an ethoxylate content sufficient to provide
detergency or wetting. Typically, the ethoxy (EO) group
to alcohol, mole/mole average ratio of the deinking
compositions range from 0.001 to 12. Hydrophobicity of
the compositions as measured hydrophobic-hydrophilic
balance (HLB) values range from 0.5 to 12. The cloud
point of the compositions are less than 200 F and
hydroxyl values (expressed as eq./100 g) are greater than
O . 0001 .
Further embodiments of the deinking compositions
have HLB values ranging from 0.5 to 6, ethoxy group to
alcohol, mole/mole avg. ratio ranging from 0.1 to 5,
cloud points in the range of 5 to 100 F and a hydroxyl
value between 0.1 and 1.
Other deinking agents which may be used in the
invention include a mixture of one or more C5 - C20
alkanols and alcohol ethoxylates in the ratio of 4:1 to
1:1.5 of alkanols to alcohol ethoxylates. Specifically,
where for every 10 parts by weight of alkanol and alcohol
ethoxylates there are between 3.0 and 8.0 parts alkanol
and between 2.0 and 7.0 parts alcohol ethoxylates.
FIGS. 2 and 3 illustrate embodiments of the
invention process. The net effect of the invention
W095/~187 216 g 5 ~ 8 PCT~S94/08774
process is to separate the defibering and agglomeration
actions. In FIG. 2, a single deinking agent containing
the combined components and functionalities of deinking
chemicals A and B are added to the mixing vessel, 14.
- 5 Alternately, in FIGS. 2 and 3, the deinking chemical
components A and B are split and added at different
points in the invention process. Deinking chemical A is
added to the pulper 12, and deinking chemical B is added
to the mixing vessel 14. This latter embodiment splits
the chemical actions of the deinking agent to permit
higher concentrations of active agents at the unit
operations where they are most effective.
FIG. 2 is a schematic view of an apparatus,
generally designated 10, for practicing the deinking
process of the invention. The process of the invention
entails defibering the wastepaper, causing agglomeration
of the ink particles with the addition of a deinking
chemical in aqueous medium, and removal of the
agglomerated ink by screening and forward cleaning.
As shown in FIG. 2, the printed paper is repulped in
an aqueous medium at hydrapulper 12 to produce a pulp
medium. The defibering of the printed paper is generally
at temperatures in the range of 25 to 45- and carried out
for a time long enough to cause separation of the paper
fibers. The aqueous medium in the mixing vessel is
maintained at a pH in the range of 7 - 11.5 and at
temperatures in the range of 40 - 90 C.
Any type of printed paper may be used in this
invention including computer printout paper, writing
paper, fine paper, coated and uncoated magazine paper,
newsprint and packaging board. This list is merely
representative of the different types of printed paper
and is not considered to be inclusive of all the possible
types of printed paper which may be used in the
invention.
WO95/04187 PCT~S94/08774
21 ~-85~8
-14-
TABLE II
TYPES OF PRINTED PAPER
COM~ul~:K PRlllO~l PAPER
WRITING PAPER
FINE PAPER
COATED/UNCOATED MAGAZINE
COATED PUBLICATION GRADES
MANILA FILE FOLDERS
NEWSPRINT
PACKAGING BOARD
The sorted printed waste paper is slushed at
consistency range between 3 and 30%, in the hydrapulper.
The repulping is preferably done in an alkali aqueous
medium, with sodium hydroxide added to speed the
repulping and to aid in the separation of ink particles
from the pulp fibers. Ambient temperature is preferred
when using highly contaminated waste in the hydrapulper
since at higher temperatures contaminants, such as
stickies, would break down making them difficult to
remove. The pulp medium may optionally be passed to a
detrashing unit (not shown), which removes large
contaminants such as large pieces of plastic or metal.
After defibering, the pulp medium is then pumped to
a mixing vessel 14 where the addition of the deinking
chemical causes agglomeration of ink particles to produce
an ink pulp medium. For effective agglomeration to
occur, low shear mixing is preferred and is achieved in
devices other than a pulper. Typically, the pulp medium
is passed to the mixing vessel for at least 10 minutes,
preferably from 20 to 60 minutes, and maintained at a pH
in the range of 7 - 11.5 at temperatures in the range of
40 to 90C. The deinking chemical is present preferably
W095/04187 21~ 8 ~ 7 8 PCT~S94/08774
-15-
at a dosage range between 0.1 to 3% by weight, calculated
on the dry weight of the pulp used.
The ink pulp medium is passed through dump chest 16
and a liquid cyclone 18, for removal of heavy
~ 5 contaminants, such as paperclips, staples and glass.
After removal of the heavy debris the ink pulp medium is
passed through a series of slotted screens 20, 22.
Preferably, the ink pulp medium, at consistencies ranging
from 0.5 to 6.0%, and temperatures from 25-55C, is
0 pA~Ce~ through slotted pressurized screens to remove
coarse contaminants and large ink particles. The coarse
screens 20, typically have hole sizes in the range of
0.040" to 0.062", and the fine screens 22, have slots of
width between 0.006" to 0.012". Preferably, secondary
and tertiary screening stages are often used for both
coarse and fine screening to reduce the loss of good
fiber from the system.
The slotted screens 22, remove a large percentage of
the stickies from the system, including adhesives from
self-stick envelopes and labels. Removal of the stickies
is critical during the deinking process. High efficiency
stickies removal by the fine screens is achieved in the
system by maintaining the screening temperature at close
to ambient temperature, so that the stickies do not
become softened and more deformable for extrusion through
the slots into the pulp accepts stream.
The ink pulp medium is diluted to 1% consistency or
less at dilution tank 24, for pumping through a set of
forward cleaners (centrifugal cleaners) 26, 28, for
removal of the agglomerated ink particles denser than
water to produce a substantially ink free pulp medium.
The large ink particles from the screening and
cleaning steps are easily separated into the cleaner
rejects, and are removed from the system for disposal by
landfilling or burning or for other uses.
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~168578
-16-
Optionally, the substantially ink free pulp medium
may be recirculated to the mixing vessel 14. The
presence of the deinking agent B causes additional
agglomeration of ink particles which are subsequently
removed by screening and cleaning procedures. In
addition, reject streams from the production of the
substantially ink free pulp medium may be recirculated to
the mixing vessel 14 where the prec~c~ of the deinking
agent causes additional agglomeration of ink particles.
The reagglomerated ink particles are removed by screening
and cleaning procedures. The further steps of
recirculating the substantially ink free pulp medium and
reject streams result in increased pulp medium yield and
produce a cleaner pulp medium.
The substantially ink free pulp is thickened 30, and
used to make recycled paper by conventional papermaking
techn; ques.
FIG. 3 is a modification of the process of the
invention in which the deinking chemical is separated
into chemical components A and B which are added at
different points in the invention process. This
embodiment splits the chemical actions of the deinking
agent to permit higher concentrations of active agents at
the unit operations where they are most effective.
In general, the printed paper is defibered in a
hydrapulper 12 and passed to a mixing vessel 14, where
deinking chemical A is added. Deinking chemical A acts
to remove ink from the pulp fiber, lower the glass
transition temperature of polymeric inks and wet the ink
particles. Preferably, deinking chemical A is an
ethoxylated nonionic surfactant, though many others may
be used as previously indicated. Contaminant removal is
achieved by passing the pulp medium through dump chest
16, liquid cyclone 18, slotted screens 20, 22. After
passing through dilution tank 24 and forward cleaning
W095/04187 216 8 ~ 7 8 PCT~S94/08774
-17-
stations 26, 28 the reject streams are passed to chest 34
where deinking chemical B is added. Deinking chemical B
is a coagulating/liquid bridging agent and is preferably
an alkanol. The presence of deinking chemicals A and B
causes agglomeration of ink particles to produce and ink
pulp medium. This ink pulp medium is recirculated to the
dump chest 14, and passed through screening and
centrifugal cleaners to remove ink particles from the ink
pulp medium to produce a substantially ink free pulp
medium.
Preferably chemical A at a dosage of 0.2 to 0.4% by
weight of pulp is added in the mixing vessel 14. This
addition helps reduce the pulping time to that sufficient
for defibering alone, 10 minutes instead of the normal 30
minutes, and allows a lower temperature to be used in the
pulper. This change would also provide for higher
throughput in the pulper.
Chemical B is added at a dosage of 0.2 to 0.5% by
weight of pulp. This leads to a 50% or more cost savings
in chemical costs and is more effective than conventional
processes.
Numerous alternative embodiments to the process of
the invention are possible. Another alternative
embodiment, is the replacement of the first set of
forward cleaners 26 with pressure screens having fine
slots, between 0.006" to 0.012" slot width, for removal
of the large agglomerated ink particles.
In yet another alternative embodiment, additional
sets of forward cleaners 26, 28 can be added in a 2, 3,
or 4 arrangement for further improvement in the
cleanliness and yield of the pulp.
A comparison of conventional agglomeration deinking
methods and the method of the invention is shown in
Example I below. In the conventional deinking process
printed wastepaper was defibered and contacted with a
WO95/04187 PCT~S94/08774
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-18-
deinking chemical in the same vessel, a hydrapulper, to
produce an ink pulp medium. Alternatively, utilizing the
process steps of the invention the printed paper was
defibered in the hydrapulper and then pAC~e~ to a mixing
vessel where a deinking agent was added. The deinking
agent used in Example I is a mixture of one or more C5 -
C20 alkanols and nonionic surfactants. Example II
illustrates the process of the invention in which the
deinking chemical is separated into chemical components
A and B which are added at different points in during the
deinking process. This embodiment splits the chemical
actions of the deinking agent to permit higher
concentrations of active agents at the unit operations
where they are most effective.
These examples are merely representative and are not
inclusive of all the possible embodiments of the
invention.
EXAMPLE I
Conventional Aqqlomeration Deinking Method
Laser computer printout (CPO) wastepaper was
repulped at 5% consistency in a Black Clawson Hydrapulper
at pH lO simultaneously with 0.8% by weight of an
agglomeration deinking agent, which is a mixture of one
or more C5 - C20 alkanols and nonionic surfactants. The
agglomeration was carried out for 30 minutes at 70C in
the pulper. Samples of the ink pulp medium were taken
after the agglomeration and labelled "Conventional".
Brightness and dirt/speck count measurements were taken.
The results are listed below in Table III.
Control
In a comparative experiment, the laser CPO was
repulped at pH 10 with no deinking agent for lO minutes.
A sample of the ink pulp medium was taken and labelled
"Repulped" and brightness/dirt/speck measurements were
carried out.
W O 95/04187 216 ~ S 7 ~ ~CT~US94/08774
--19--
~ Invention Agqlomeration Deinking Method
The Repulped sample, from the control experiment, at
5% consistency was transferred to a 5 gallon vessel. The
same agglomeration deinking agent as used in the
Conventional method was added at 0.8% by weight of pulp.
The temperature was maintained at 60-C with continuous
stirring using a "Lonar" stirrer to provide sufficient
mixing for 30 minutes. Brightness/dirt/speck
measurements were taken on this ink pulp medium and
labelled "Modified". The results are tabulated below in
Table III.
EXAMPLE I
TABLE III
SAMPLEBRIGHTNESS DIRT COUNT % DIRT
(G.E.) (ppm) REDUCTION
REPULPED74.02(0.41) 10194 0
COhv~NllONAL 75.98(0.32) 8476 16.9
MODIFIED77.48(0.37) 7800 23.5
Note: Numbers _n parenthesis are the st~n~rd deviatio
in the sample.
The results clearly demonstrate the invention
process increases the % dirt reduction over conventional
agglomeration deinking processes. The separation of the
defibering and agglomeration actions produce a pulp of
higher brightness and lower dirt count. Thus the
invention process increases the agglomeration action
which results in cleaner pulp and higher yield. The
additional advantages of the invention process are higher
- throughput, no pulper capacity limitation and lower
temperatures for agglomeration.
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EXAMPLE II
Twenty five pounds (25 lbs) of sorted white ledger
(SWL) was added to 35 gallons of water at 70C and
repulped for 5 minutes. A sample, labelled A, was taken
after repulping and measured for brightness and dirt
count. The results are listed below in Table IV. The
remaining repulped sample was split into sample B and C
and treated with a deinking chemical comprised of a
mixture of C1216 alcohol ethoxylates and C1012 alkanols by
the following processes.
To sample B, 0.8% by weight of a mixture of 1.25:1
blend of Alfol~1012 to Alfonic~1216-22 was added.
Alfol~1012 is a blend of C10.12 alkanols and Alfonic~1216-
22 is C1216 alcohol ethoxylates, both chemicals are from
Vista Chemicals, Houston, Texas. Sample B was repulped
with the deinking agent for 30 minutes at 70C.
Brightness and dirt count measurements were taken and
listed below in Table IV.
In sample C, the same deinking chemical and
component proportions were used, however, the components
were added during separate process steps. First the same
amount of Alfonic~1216-22 used in sample B was added to
sample C and repulped for 10 minutes. Five gallons of
the Alfonic~1216-22 treated sample was transferred to a
vessel where Alfol~1012 was added at the same percent
weight based on oven dry pulp as in sample B. The
mixture was stirred for 30 minutes at 70C. Brightness
and dirt count measurements were taken and listed in
Table IV.
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EXAMPLE II
TABLE IV
BRIGHTNESS DIRT COUNT SPECK COUNT
SAMPLE (% G.E.) (mm /m of (#/sq.m)
sheet)
A 74.4 10,879 156,905
B 74.3 5,300 88,921
C 77.1 5,310 83,381
The brightness data in Table IV shows an increase in
brightness of 2.7% GE when the chemicals are added
separately (sample C). This is due to improved
agglomeration, i.e. fewer small ink specks. The average
particle size at the end of the conventional treatment
(adding both components together- sample B) is 0.059
sq.mm. On the other hand when we split the components
and add them as necessary, then we increase the average
particle size to 0.064 sq. mm (sample C). This
demonstrates that split chemical addition provides for
improved agglomeration.
The simplicity of the equipment used and the high
amount of ink removal make the agglomeration deinking
process of the invention advantageous over prior art
practice.
Advantageously, the method of this invention for
deinking printed paper is less complex than conventional
deinking processes involving washing and flotation
procedures and known agglomeration procedures.
It will be r~cognized by those skilled in the art
that the invention has wide application in deinking a
variety of printed paper to produce recycled paper.
There are numerous advantages to separate the
defibering and agglomeration actions over conventional
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agglomeration deinking proceCc~c in which the actions
occur simultaneously under the same conditions. Overall
improved effectiveness in agglomeration deinking, lower
chemical costs, fewer screening/cle~ning steps are
generally required and improved hydrapulper utilization
are among some of the advantages to the process of the
invention.
Specifically, advantages of the process of this
invention include the increased utilization of pulper
capacity which can be a serious limitation in commercial
operations. Through better pulp and deinking chemical
utilization more effective agglomeration occurs leading
to better ink removal and increased yield of brighter,
cleaner pulp. The higher effectiveness of the
agglomeration step leads to lesser equipment requirements
and decreased capital costs. The invention process also
adds deinking chemicals at points where they would be
most efficient and could lead to a lower dosage of
chemicals used.
Numerous modifications are possible in light of the
above disclosure such as application of alternative
agglomeration deinking chemicals chosen according to the
wastep~per treated. In addition, alternative process
parameters may be employed in the invention, which
include using the deinking agent with no pH adjustment to
the wastepaper; using the deinking agent in an alkali pH
range; or using the deinking agent in the presence of
WO95/04187 216 ~ ~ 7 8 PCT~S94/08774
other chemicals suitably employed in a deinking and/or
papermaking process such as bleaching agents, defoamers,
sizing agents, brighteners, water quality processing
agents among others.
Therefore, although the invention has been described
with reference to certain preferred embodiments, it will
be appreciated that other composite structures and
processes for their fabrication may be devised, which are
nevertheless within the scope and spirit of the invention
as defined in the claims appended hereto.
