Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM FOR CONTROL OF STICKIES IN RECOVERED AND
VIRGIN PAPER PROCESSING
BACKGROUND OF THE INVENTION
The present invention relates to paper making processes and more
particularly relates to enhanced removal and the control of adhesive
contaminants and stickies in recovered paper processing.
Conventional recycling of old paper products such as old newsprint,
old corrugated containers, and mixed office waste is an important aspect of
paper production today due to environmental demands that many paper
grades have a portion of recycled fibers contained within the paper product.
However, the recycling of the recovered paper generally requires additional
processing steps in order to produce pulp, which is suitable for use in the
final recycled paper product.
Conventional recycling of recovered paper to produce pulp
coinparable to that used to originally make the virgin sheet is known in the
art as "de-inking," and typically involves pulping, soaking, screening,
cleaning, washing, flotation, dispersion, thickening, and bleaching steps.
Conventional recycling is usually conducted with surfactants, bleaching
chemicals, chemicals for water treatment, and other polymeric treatments,
and may use strong alkali treatments to solubilize insoluble contaminants.
Generally, the first step in conventional recycling is to disassociate the
paper
into individual fibers with water to form a pulp slurry and to detach the ink
and contaminants from the fibers, followed by removing ink and
contaminants from the fibers by a combination of various process steps, such
as screening, centrifugal cleaning, washing, dispersion, thickening, and
flotation. The screening and centrifugal cleaning steps remove large
contaminants, such as paperclips, staples, and plastics. The primary purpose
of washing and flotation steps is to remove the ink and contaminants' from
the stock. Surfactants and alkaline agents such as caustic are added to
facilitate the modification and separation of contaminants from the fibers.
Alkaline agents may cause yellowing of the fibers, which must then be
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bleached. The fibers may or may not then be blended with virgin fibers and
used in the papermaking process.
Recent developments in waste paper de-inking make use of enzymes
to aid in the detachment and removal of inks and contaminants from the
fibers. These processes describe the use of particular types of enzymes to
facilitate ink removal without the negative effects of caustic treatment on
brightness along with the use of flotation, washing, cleaning, and screening.
In the past, chemical additives have been added to remove or make less
problematic organic contaminants, known as "stickies." Stickies are
generally adhesives, glues, hot melts, coatings, coating binders, ink
residues,
deinking chemicals, wood resins, rosin, pitch, and unpulped wet strength
resins that typically are present with the fiber to be recycled. These organic
contaminants typically must be removed or pacified in substantial quantities
so that they do not detrimentally affect the subsequent processing steps in
the
deink plant, the paper machine, and with the printer or user of the final
recycled sheet. Stickies have a broad range of glass transition temperatures
and melting points and different degrees of tackiness depending upon the
composition of the stickies. Temperature, pH, and composition can affect the
tackiness of stickies. Recycled paper contains many components that, when
repulped in recycled fiber plants, become stickies. Recycled furnishes may
have as many as a dozen different types of stickies, each having its own
characteristics. Sources of stickies may include any of the following:
adhesives, glues, hot melts, coating binders, ink residues, deinking
chemicals, wood resins, rosin, pitch, and wet strength resins. The actual
tacky deposits found on paper machines may be a combination of several of
these organic contaminants including fines, fibers, and ink particles as well
as inorganic particles such as talc, clay, or calcium carbonate.
"Stickies" can generally be divided into two categories: synthetic and
natural materials. Examples of synthetic materials include adhesives such as
styrene-butadiene copolymer (SBR), polybutradiene (PBD), polyisoprene
(PIP), polyacrylate, polyethylene (PE), and polypropylene (PP); hot melts
such as waxes, resins, vinyl acrylates, and poly(vinyl acetate) (PVA); ink
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residues such as mineral oils, resin esters, alkyd resins, styrene-acrylates,
polyacrylates, and epoxy acrylates; and wet-strength chemicals such as urea-
formaldehyde and melamine-formaldehyde. Examples of natural materials
include wood resins, resin and fatty acids or esters such as resin acids,
fatty
acids, and resin and fatty salts.
Stickies deposits on paper machine surfaces, fabrics, wires, felts, and
rolls lead to problems such as wet end breaks, pressroom breaks, dryer
section breaks, holes, sheet defects, high dirt counts, and difficulties in
paper
converting. These deposits and associated problems lead to a significant
amount of downtime and waste. The cost of stickies is considerable, when
factoring in the cost of downtime, chemical costs, production losses, scrap,
rejected materials, and customer complaints.
Some mills control stickies by using wastepaper grades that contain
less stickies. These grades are becoming more difficult to find and are sold
at much higher prices. To manage the stickies present in the wastepaper, a
number of different methods have been described for use in stickies control.
The removal methods may be divided into two groups, mechanical methods
such as cleaning, screening, and dispersion, and physicochemical methods
such as flotation, washing, detackification, pacification, and coagulation and
agglomeration. Stickies control strategies may use multiple approaches.
Screening typically removes larger or macro stickies (>1.0 mm2).
Forward and reverse cleaners can be used based on density differences using
centrifugal force. Forward cleaners remove containinants heavier than water
and reverse cleaners remove particles lighter than water. Cleaning removes
more macro stickies than micro stickies. Flotation removes intermediate-size
stickies (50-300 microns), which are troublesome because they are small
enough to pass through screening and cleaning but too large to be removed
by washing. In disperging, the stock is thickened, passing through a device at
high temperature, pressure, and shear, which breaks organic contaminants,
including stickies, into smaller pieces.
Physicochemical methods remove or control stickies by modifying
the surface properties of stickies through either adsorption of adsorbents or
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addition of other chemicals or in combinatioxs, so that the stiekies can be
easily removed or pacified, The methods include flotation, waslring, addition
of solid materials, treatment with suxfactants and polymers.
For instance, in pacification, additives like ta1c, clay, nonionic
organie polymers, other inorganic particles, and enzymes are used to render
the sticIdes less tacky. Knudsen, et al., "I.ong-term Use of Enzymatic
Deinldng at Stora Dalum Plant, 7s' Intemationai Con~erenoe on
Biotechnology, in the Pulp Paper Ind., vol. A, June 1998, p. 1-4, genetally
refers to the use of enzymes to reduce sticldes in recovered paper. Sykes, et
al., 'Bnzymatic Removal of Stic1Qe Contaminants" Pulping Conf.1997, pp.
687-691 descxibes the use of cellulase, lipase or a mixture thereof to reduce
stickies contaminants. See also Wong and 1Vlans$eld "Enzymatic processing
for pulp and paper manufacture" APPrT'A J. 52(6):409-418 (1999) and U.S.
Patent No. 6,471,826. A method of treatment paper pulp to eliminate or
restrict organic compounds derived from pitch is described In WO 95/07385.
At various stages of the recycling process, dispersants, surfactants, and
solvents are used to make stickies smaller. Some other approaches use
chemiaals to agglomerate the stickies to enhance their removal though stages
such as screaning, Still other chemical treatments aim to make the stickies
more hydrophobic to enhance removal through flotation or more hydrophilic
to enhance their removal through washing. With Sxation treatments, the
stickies are attached to the paper sheet by usino a water soluble polymer,
which adds charge to the stickies particles.
With dispersing and fixation treatments, a dispersant is added first to
reduce the size of the stickies and then a cationic polymer is nsed to fix the
stickies onto the sheet. With passivation, the use of dispersants, solvents,
and
low molecular weight cationic polymers makes the paper machine less
susceptible to stickies,
Unfortunately, even with the best of all of these methods, too many
of the stickies are still present in the fmal product to avoid problems.
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095146100008
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It is therefore an object of the present invention to provide e-ohanced
stickies removal and control from recycled paper systems and virgin fiber
processing.
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SUMMARY OF THE INVENTION
Enhanced removal and/or control of adhesives materials, "stickies",
from recovered or recycled paper stock and virgin fiber processing is
achieved using a combination of enzyme treatment with adsorbents and/or
absorbents. Recovered paper stock to be treated is typically obtained from
old magazines, newspapers, home waste or office waste, but may include
corrugated cardboard boxes and other sources of recovered fiber. Enzymes
typically include hydrolases such as cellulases, hemicellulases, amylases,
proteases, (3-glucosidase, lipases, esterases, and pectinases, lyases such as
pectate lyase and oxidoreductases such as laccase, glucose oxidase, and
peroxidases. Individual enzymes or any combinations of different varieties
may be applied together with absorbents or adsorbents. Adsorbents include
bentonite, both activated and non-activated, microparticles, talc, clay and
modified silica gel. Absorbents typically include water soluble polymers,
which can be either cationic or anionic. Dispersants may also be used.
Waste paper is initially treated in a pulper to make a slurry, which is
screened mechanically and/or cleaned centrifugally and/or passed through a
washer, flotation process, or a disperger to remove large pieces. Enzymes
may be added in the pulper or later in the system, including before the paper
machine. Exemplary stages where enzymes may be applied include the
dump chest, soaking tanks, flotation, washer, water treatment, and storage
chests. Preferably the enzymes are selected so that they have optimal
activity at the pH and temperature range where the pulp is to be treated. In
the preferred embodiment, the adsorbent/absorbent is added to the pulp
slurry, preferably in a 1%-5% slurry by weight at a dosage of between about
0.05 to 2.0% of solids per air dried ton of wastepaper. The
adsorbent/absorbent can be added to the pulper, dump chest, flotation or
washer, bleaching, disperger, water clarifier, prior to the paper machine, or
prior to or in any stock storage tank. Good mixing is preferred to insure that
the material is thoroughly mixed with the stock and that stickies come in
contact with the enzymes, absorbents and or adsorbents.
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Examples demonstrate significantly more reduction with the
combination of enzymes and adsorbents or absorbent, than treatment with
either alone and is significantly more than an additive result.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic of an example mill flow sheet showing points
at which enzymes and adsorbent/absorbent can be added.
Figure 2 is a graph of stickies count (relative stickies deposit, %), for
a control test (100% is the stickies level with normal mill processing),
enzyme treatment alone ("Enzynk E4946"), activated bentonite treatment
alone, and the combined enzyme treatment plus activated bentonite
("Enzynk E4946 plus bentonite"). The furnish treated was a 60/40 blend
of US mixed office white ledger waste and office pack. Treatment was made
under highly controlled laboratory conditions. Stickies tests were made from
mixing identical quantities of stock at 8% consistency in a Kitchen Aid
mixer for 60 minutes followed by visual examination of the deposits on the
mixer blades. The analysis is measured on the percent coverage of the
leading blade by stickies.
Figure 3 is a graph of the stickies count (area, ppm) for a control test,
enzyme treatment alone ("Enzynk(D E2028"), activated bentonite treatment
alone, and the combined enzyme treatment plus activated bentonite
("Enzynk(V 2028 plus bentonite"). A dosage of 1.5 kg Enzynk E2028 per
ton of wastepaper and 4.0 kg bentonite per ton mixed office wastepaper were
added in the pulper. Analyses consisted of light microscope examination of
filtrate of machine chest stock after having been passed through a machine
fabric.
DETAILED DESCRIPTION OF THE INVENTION
A method to enhance removal and control of stickies from fibers has
been developed. The fibers are typically cellulose fibers and more typically
are recycled fibers from a variety of paper products or fiber containing
products, such as old corrugated containers (OCC), old newsprint (ONP),
mixed office waste (MOW), household waste (HW), other recovered paper
varieties, or combinations thereof. These types of paper containing products
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typically include significant amounts of organic contaminants that are sticky
in nature. When these types of paper products are recycled, sticky organic
contaminants are present along with the fibers during the pulping stage of a
papermaking process. These organic contaminants, if not substantially
removed or pacified, can severely interfere with the subsequent stages in the
papermaking process or with the enduser by affecting the quality of the
resulting sheets of paper formed and/or affecting the machinery used to
produce the paper. Accordingly, the removal or pacification of such organic
contaminants is important to the paper making process when such organic
contaminants are present in fibers.
Examples of organic contaminants that are known in the industry as
"stickies" include, but are not limited to, synthetic polymers resulting from
adhesives, glues, hot melts, coatings, coating binders, ink residues, de-
inking
chemicals, wood resins, rosin, and wet strength resins. These types of
materials are typically found in paper containing products, such as newsprint,
corrugated containers, household waste, and/or mixed office waste. These
organic contaminants typically will have polymers present, such as styrene
butadiene rubber, vinyl acrylates, polyisoprene, polybutadiene, natural
rubber, ethyl vinyl acetates, polyvinyl acetates, ethylvinyl alcohols,
polyvinyl alcohols, styrene acrylates, and other synthetic types of polymers.
The enhanced removal is achieved through a combination of (1)
enzyme treatment, using one or more enzymes and (2) treatment with
adsorbent and/or absorbent.
As used herein, enhanced removal, pacification and/or control of
stickies refers to a reduction in the size of particles and/or a reduction of
the
number or amount of measurable particles present, and/or a reduction of the
tackiness of the organic contaminants.
Measurement of stickies can be done through many procedures. One
procedure uses a fine slotted screen, such as a Pulmac Master Screen, to
screen out large contaminants and then use multiple methods to separate and
measure the stickies components. One such method uses heat and/or
pressure to press the rejected contaminants against a surface, such as a sheet
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or clear overhead transparency such that the stickies are transferred to the
sheet or transparency and the stickies can be counted manually or through
image analysis. Variants on this approach use dyes to color the stickies prior
to counting or scanning. A vibrating slotted screen, such as a Summerville
Screen, can also be used to separate the contaminants from the stock. Still
other tests use powders, either dark or light in color, which are transferred
to
the sticky reject contaminants with the resulting powder stuck on the stickies
being scanned for area. Microscopic techniques can also be used to measure
microstickies, such as visual inspection of pulp stock filtrates with an
assessment by particle size of stickies viewed by light microscope. Stickies
counts are usually measured as count or ppm area per fixed quantity of pulp
(e.g., per 100g air dried fiber).
1. Compositions and Systems for Reduction in Stickies
Compositions for removal or reduction in stickies are typically sold
as a two component treatment system including at least two components: one
or more enzymes and adsorbents/absorbents. Treatment systems may
include other additives. Materials will typically be shipped together, but
packaged separately, for administration in the appropriate amounts and in the
optimal forms at different stages in the processing. For example, many of
the inorganic materials are best added in low consistency slurries, so they
are
typically shipped to mills as a dry product. A typical process is depicted in
Figure 1.
A. Enzymes
Enzymes are used to modifiy stickies particles. Representative
examples of useful enzymes include esterases, lipases, hydrolases such as
cellulases, hemicellulases, amylases, pectinases, (3-glucosidases, and
proteases, lyases such as pectin lyase, and oxidoreductases such as laccases,
glucose oxidases, and peroxidases, typically added in an amount of between
0.0005% and 0.5%based on air dried ton of fiber, more preferably between
about 0.0025 and 0.25% based on air dried ton of fiber. These are
commercially available from a number of different suppliers.
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Lipases can be derived or isolated from pancreatic sources (e.g.,
pancreatic lipase) or from various fungi and/or bacteria, and/or other
microorganisms. Examples include triacylglycerol acylhydrolase and triacyl
glycerol lipase, lipases and esterases capable of hydrolyzing triglycerides to
glycerol and fatty acids. Enzymes can be obtained from Enzymatic Deinking
Technologies, Norcross, Georgia, USA. Commercially available products
containing esterase or lipase can be used such as Buzyme.RTM 2515 and
Buzyme.RTM 2517, available from Buckman Laboratories International,
Inc. Products containing such enzymes as Resinase A2X, Novocor ADL,
Pancreatic Lipase 250, Lipase G-1000, Greasex 50L, and Greasex 100L
products are available from such commercial sources as Genencor and Novo
Nordisk. Esterases and lipases are described in U.S. Patent Nos. 5,507,952
and 5,356,800. The esterase and lipase compositions can also be stabilized
compositions using the formulations described in U.S. Patent Nos. 5,356,800
and 5,780,283.
Enzymes can generally be used in any form, such as liquid form or
solid form. They can either be added to the pulper in a preferred
embodiment or later in the deink plant system, or even in the chest prior to
the paper machine. Preferably, the amount of esterase, other lipase, other
hydrolase, or other enzyme variety used in the methods is in a sufficient
amount to control the organic contaminants present in the fiber. Individual
enzymes or any blends of these enzymes may be applied in an amount of
between 0.0005% and 0.50% based on air dried fibers, preferably between
0.0025% and 0.25%, and most preferably between 0.05% to 0.15% based on
air dried fibers, in an amount of sufficient quantity to provide a meaningful
degree of reaction with the targeted substrate. Other enzymes used in this
method such as other hydrolases and other enzyme varieties can be added in
similar points of the process, individually or in any combination with
esterases such as lipases. Enzyme application on virgin stock to control
natural stickies can be made in one of several storage tanks in which the
pulped stock is held or prior to the paper machine.
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B. Adsorbents and Absorbents
A variety of different adsorbents and absorbents can be used. The
difference between adsorbents and absorbents can be determined when a
material extracts one or more substances from a fluid (gas or liquid) medium
on contact. If the material undergoes any physically and/or chemical changes
or both, it is an absorbent; otherwise it is an adsorbent. Both absorbent and
adsorbent are usually porous solids, which take another material into its
interior resulting from contact. The mechanism of an absorbent is to
encapsulate the stickies particles within crevices of the absorbent for the
purpose of covering the sticky surface or binding the stickies particles with
a
material that is hydrophobic or hydrophilic and would enhance the removal
of the stickies contaminant. Adsorbents are used to attach to the stickies
particles for similar purposes of covering part of the sticky surface or
making
a stickies/adsorbent complex that is more hydrophobic or hydrophilic or
otherwise easier to handle with mill equipment.Preferred materials have a
higli surface area. These may be in the form of powders, particles, gels,
beads or microparticles, and added in dry form or as a liquid slurry.
The most preferred materials are clay, bentonite, silica gel or
colloidal silica, and talc. Acid or alkaline activated bentonite having a high
surface area of 400-1000 m2/gram or more is most preferred. Modified silica
beads are also preferred. In both cases the adhesives enter and bind into the
crevasses and are encapsulated within the materials. Materials such as talc
tend to bind the adhesives on their surfaces.
These materials are usually added as a water slurry, typically of
0.05% to 10.0% consistency in water and more typically between 1.0% and
5% consistency in water. Dosing of the absorbent or adsorbent is expressed
in weight of absorbent or adsorbent to air dried stock and is in the range of
0.005% to 5.0%, more preferably 0.05% to 3.0%, and most preferably
0.10% to 1.5%.
C. Other Additives
Water soluble polymers such as a cationic water soluble polymer can
be used to attach the stickies to a substrate for removal. Examples of such
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polymers include epichlorohydrin/dimethylamine polymers (EPI-DMA) and
cross-linked solutions thereof, polydiallyl dimethyl ammonium chloride
(DADMAC), DADMAC/acrylamide copolymers, and ionene polymers.
Examples of ionene polymers include those set forth in U.S. Patent Nos.
5,681,862, 5,575,993, and 5,256,252. The polymer can be used in any
amount and preferably in dosage ranges of from about water soluble polymer
added in a dosage range of from about 0.1 to 1000 ppm, more preferably 1.0
to 100 ppm, and most preferably 2.5 to 10 ppm.
Other materials include dispersants such as surfactants which could
include, but are not limited to, soaps, fatty acid alkoxylates, fatty alcohol
akloxylates, and EO/PO polymeric surfactants. Other conventional paper
treatment chemicals or ingredients such as solvents, suspension aids, fillers,
chelants, preservatives, buffers, water, and stabilizers can also be added
during processing.
II. Methods of Treatment
Each mill may utilize a different process, depending on the material
to be recycled, nature of the problem, water loops, age of plant, end use, and
goals from the treatment. Individual enzymes or a blend of any
combinations of enzyines may be applied with or without the absorbents or
adsorbents. A typical mill scheme is shown in Figure 1. As shown in Figure
1, pulp is created in a pulper 10, passed through screens 12, optionally
through a primary flotation 14 and cleaners 16, then washers 18, thickeners
20, then disperger 22, then bleaching 24, optionally a secondary flotation 26,
thickener 28, then a wet lap machine 30 or in the case of integrated use,
through a storage chest 32 and then on to the paper machine. Water from the
dewatering stages may pass through water clarification such as a dissolved
air flotation unit 19 and 29.
Enzymes are typically added into the pulper 10, which is used to mix
the enzymes thoroughly through the pulp and utilize the time in the pulper
and the time in the dump chest for the reaction of the enzymes. Typical
pulping cycles may take up to 60 minutes and mixing time in the subsequent
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dump chest may be up to 240 minutes. Enzymes typically include
hydrolases, lyases, and oxidoreductases. Individual enzyme or any
combinations of them may be applied together with absorbents or adsorbents.
Hydrolases include cellulases, (3-glucosidases, hemicellulases, pectinases,
amylases, proteases, and esterases and other lipases, which may break down
poly (vinyl acetate) types of stickies materials. Lyases include pectate
lyases,
which may break down the pectin types of materials holding the stickies
particles together, or break the stickies particles free from fines.
Oxidoreductases include laccases, peroxidases; which may modify other
impurities attached to stickies particles and make the stickies particles more
hydrophobic or hydrophilic or free from fibers and/or fines in order to
enhance either the stickies removal or make them less troublesome to paper
recycling or papermaking processes. These enzymes may be applied
individually or in any combinations and the treatment time be from 1 minute
to 16 hours, preferably 10 minutes to 4 hours and most preferably 30 minutes
to 60 minutes. The enzymatic treatment pH may be in a range of between 3.5
to 12.0, and preferably between 4.5 and 9.5. The temperature of enzymatic
treatment may be in a range of between 35 C and 90 C, and preferably
between 40 to 75 C. The dosage of enzymes may be from 0.0005% to 0.50%
based on air dried fibers, more preferably from 0.0025% to 0.25%, and most
preferably from 0.05% to0.15% based on air dried fibers.
Enzymes can also be introduced prior to the pulping stage, typically
by spraying or other means, onto the paper containing product which is
going to be introduced into the pulper. Also, or alternatively, the enzymes
can be present or introduced into the pulper during the pulping stage which
can be by any conventional pulping technique such as mechanical pulping or
chemical pulping for virgin fibers and batch, semi-batch or continuous
pulpers for recycled fiber treatments, or combinations thereof. The enzymes
can be introduced or brought into contact at any stock storage chest, other
holding tank, or prior to the flotation deinking -stage. In one embodiment,
the
enzymes are introduced after the flotation stage and prior to a washing stage.
In another embodiment enzymes are applied prior to fine screens, and in
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another embodiment enzymes are applied before the paper machine. The
composition can also be administered into the paper machine white water or
in the makeup water in the deinking plant. Alternatively, the enzymes can be
applied in the water treatment loops of virgin or recycling mills to treat
stickies in the water filtrates.
Absorbent and/or adsorbent is added to the pulper, dump chest -
flotation cells or mixing cells, washer, bleaching storage chest disperger, in
the water treatment process, and in tanks holding the final product or prior
to
the paper machine. Material is mixed such that the absorbent/adsorbent
achieves a suitable coverage of the stock and stickies particles. Longer
residence time after the materials are mixed with the stock can be helpful,
but is not necessary. The absorbents and/or adsorbents may be applied
before, after and/or together with enzymatic treatment. The dosage of the
adsorbents and/or absorbents is between 0.005% and 5.0%, more preferably
between 0.05% and 3.0%, and most preferably between 0.10% and 1.5%
based on air dried fibers. The stock pH may be between 3.5 to 12.0, and
preferably between 4.5 and 9.5. There is no limit on the application
temperature of absorbents and/or adsorbents into the recycling process.
The introduction of these materials can be immediate, slow release,
timed release, intermittent, and/or continuous. Adsorbents/Absorbents can
remain with the material as it is processed, since the stickies are trapped
and
no longer freely distributed within the fiber slurry to be processed.
Typically, the remaining aspects of the papermaking operation as is
known to those skilled in the art can be used in order to produce paper
products. Thus, the conventional additive materials used with paper making
pulps during stock preparation and papermaking can be used as well as the
combination of enzymes and absorbents/adsorbents for stickies reduction.
Continuous or non-continuous paper making machines can then convert
aqueous suspensions of fibers and other ingredients into dry sheets of paper
using such conventionally known operations which involve Fourdrinier
machines or cylinder machines or other papermaking devices. Subsequent
treatments of the sheets of paper to achieve the desired characteristics such
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as machine calendaring and/or coating of the paper sheets can be used
following treatment.
The present invention will be further understood by reference to the
following non-limiting examples.
Example 1: Comparison of treatment with enzyme alone, absorbent
alone, and enzyme in combination with absorbent under controlled
conditions.
A comparative study was conducted to look at stickies removal using
enzymes (Enzynk E4946, a mixture of acid and neutral cellulases,
amylases, and lipases obtained from Enzymatic Deinking Technologies,
LLC, Norcross, GA, USA) treatment alone, activated bentonite treatment
alone, and the combination of enzymes and activated bentonite treatment, in
the laboratory in a Kitchen Aid mixer under highly controlled conditions of
temperature, time (one hour), dosage, mixing conditions, and stickies.
The furnish treated was a 60/40 blend of US mixed office white
ledger waste and office pack. A 1.5 kg quantity of the furnish was pulped in
a high consistency pulper. Stickies were contributed from the waste paper
plus an additional amount was added to ensure the batch contained a high
quantity of stickies. Stickies added were 1 page of Avery Labels (#5160), 5
pieces of C-Line Products Border Badges, 10 pieces of 3M Post-It Notes,
and 5 pieces of 3M Post-It Fax Pads. Both the enzymes and the bentonite
were added with the wastepaper at the beginning of the pulping process.
The results are shown in Figure 2. Using the amount of stickies
remaining without additional treatment as 100%, a reduction of 30% was
obtained using enzyme treatment only and a reduction of 45% was obtained
using bentonite treatment only. The combination removed 75% of the
stickies, a result not predictable based on the use of either treatment alone.
Example 2: Large Scale Study Comparing Enzyme Treatment Alone,
Absorbent Alone, and the Combination of Enzyme and Absorbent.
This study was conducted at a waste paper processing mill under
normal processing conditions. Materials were added at the pulper. 1.5 kg
Enzynk E2028 was added per ton wastepaper and 4.0 kg EnzAid A3300
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(activated bentonite) was added per ton mixed office wastepaper. The
Enzynk E2028 is a mixture of acid and neutral cellulases, amylases, and
lipases and the EnzAid A3300 is an activated bentonite treatment.
Enzymes and bentonite were added at the pulper. Analyses consisted of light
microscope examination of filtrate of machine chest stock after having been
passed through a machine fabric.
As shown in Figure 3, the stickies count (area, ppm) is significantly
reduced by enzyme treatment alone and by bentonite treatment alone, from
3.50 to 2.62 and 2.52, respectively. However, treatment with the
combination of enzyme and adsorbent provides an even more striking
reduction as measured in the machine chest, from 3.50 with no treatment to
1.22 with the combination treatment. This degree of reduction could not
have been predicted based on the results obtained with the individual
treatments.
