Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE
8EP~RATION OF CE~ 08IC AND NON-CELL~08IC
FRACTIONS FRO~ PAPER PROD~CT8
FIELD OF THE INVENTION
5The present invention relates to a process for
the separation of cellulosic fibres from non-cellulosic
fractions in paper products. In particular, the present
invention relates to the separation of cellulosic fibres
from thermoplastic polymer film and/or metallic foil in
paper products having combinations of such components. In
particular aspects, the invention relates to the recycling
of absorbent sanitary paper products, coated paperboard and
the like. As used herein, absorbent sanitary paper
products include disposable diapers, incontinence products,
feminine hygiene products, bed pads and other related
absorbent and adsorbent products. Coated paperboard
- includes beverage and juice boxes and other laminates of
cellulosic fibres and thermoplastic polymers, some of which
also contain metallic foil.
BACKGROUND OF THE INVENTION
Absorbent sanitary paper products typically
consist of (i) a non-woven sheet formed from a liquid
permeable material, for example a liquid permeable membrane
formed from polypropylene, polyethylene, or woven products
formed from cotton or rayon, (ii) a liquid impermeable back
sheet formed from for example polyethylene, polypropylene,
starch based degradable plastic films, woven cloth or
rubber, and (iii) an adsorbent or absorbent core of air
laid wood pulp fluff, commonly referred to as air felt,
and/or synthetic pulp including polypropylene or
polyethylene filaments that may be bonded or unbonded, hemp
or other adsorbent fibrous material. The core is typically
wrapped or encased in a creped envelope of wet strength
tissue paper or a material with similar characteristics.
The wrapping on the core may or may not be breathable,
biodegradable, odour degradable or degradable or
dissolvable by other means. The core usually also contains
a super absorbent polymer (SAP) material, which is
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typically a polyacrylate, polyacrylamide, crosslinked
starch or other hydrophillic component, which may be
synthetic, and may be in granular, fibrous or laminate
form, possessing the ability to bond with water, urine or
other body fluids or retain them without substantial
release or discharge from the absorbent portion. Diapers
and incontinence products typically utilize pressure
sensitive adhesives ~or refastenable tape tabs or similar
closure m~ch~nisms. Feminine hygiene pads and incontinence
products often use pressure sensitive adhesives for glue
lines to attach the pad or liner to the user's
undergarments. Diaper and incontinence products typically
utilize elastic, polyurethane, puckering and welding or
adhesives to create close fitting cuffs around the leg and
waist openings to provide a more leakproof fit.
There is an increasing volume of coated
paperboard in which one or both sides or faces of the
paperboard have been coated with thermoplastic polymer film
or thermoplastic polymer film and e.g. aluminum foil. The
resultant coated paperboard is used, in particular, in the
beverage industry, for example, in the packaging of fruit
juices, other liquid drinks, e.g. flavoured and sweetened
aqueous drinks of various kinds, milk and a variety of
other beverages. The coated paperboard used in this
industry tends to be coated on both sides with an outer
layer of a heat sealable thermoplastic polymer, for
example, polyethylene or related polyolefin. Such coatings
serve the dual purpose of providing a barrier to retain the
li~uid within the beverage container as well as a means by
which the beverage container may be shaped and formed and
retained in its formed shape e.g. using heat sealing
techniques. The coated paperboard may have a layer of
aluminum or other metallic foil, usually as an intermediate
layer between the thermoplastic polymer and cellulosic
fibre layers.
Absorbent sanitary paper products and coated
paperboard products, and other related types of products,
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are normally disposed of along with garbage generated by
households, institutions, hotels and the like, by
incineration or in landfill disposal sites. Incineration
tends to result in air or other pollution being
generated. Landfill disposal results in an accumulation
of such products. Society is increasingly dem~nA~ng
alternate methods of disposing of such products, and
especially methods leading to recycling of components.
A process for the treatment of absorbent sanitary
paper products in order to separate cellulosic fibres
from other materials e.g. plastic layers, is disclosed in
published PCT application WO 92/07995 of M.E. Conway et
al, published May 14, 1992. A process for the treatment
of coated paperboard is disclosed in the patent
application of M.E. Conway and S.A. Martin filed
concurrently herewith.
WO 91/17304, published November 14, 1991, discloses
a method for separating plastic particles from
suspensions using turbulent flow to separate the
particles and scoops to separate lighter plastic
particles from the surface of the suspension. EP 0 570
757, published November 24, 1993, discloses a method of
separating paper fibre from mixed waste materials by
agitating the waste material in a hydrapulper. U.S.
4,129,259, issued December 12, 1978, discloses recovery
of paper fibre for re-use from waste paper materials
containing plastic sheet using a pulper equipped with a
junk remover.
SU~ RY OF THE I~V~NL1ON
An improvement has now been found in processes for
the treatment of absorbent sanitary paper products and
plastic coated paperboard, especially processes intended
for recycling of cellulosic fibres and other components,
in which thermoplastic polymer and/or metallic foil is
separated from an aqueous solution containing such
products in a comminuted form.
A~ENDEDSHc~
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Accordingly, one aspect of the invention provides a
process for the separation of cellulosic fibres from non-
cellulosic fractions, said non-cellulosic fractions
comprising at least one of thermoplastic polymer and
metallic foil, comprising:
(a) vigorously admixing paper product in aqueous
solution in a vessel, said paper product being in a
comminuted form and said vessel being such that the
solution has a surface within the vessel, said admixing
being effective for at least partial separation of
cellulosic fibres from thermoplastic polymer and metallic
foil and to form a suspension of cellulosic fibres so
separated in the aqueous solution; and
A~Na'9 S~ET
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(b) separating a fraction comprised of at least
one of thermoplastic polymer and metallic foil from the
surface of said aqueous solution in the vessel using a
bucket conveyer, said bucket conveyer extending below the
surface of the aqueous solution and discharging the
fraction so separated outside of said vessel.
In a preferred embodiment of the process of the
invention, the bucket conveyer has buckets with orifices
therein attached to a conveyer belt.
In another preferred embodiment of the process of
the invention, the bucket conveyer has at least two tynes
extending from a conveyer belt, especially 3-6 tynes.
In another embodiment, the paper product is
comminuted prior to being fed to the vessel, and in
particular is in a shredded form.
In yet another embodiment, the paper product is
comminuted in the vessel, and in particular the vessel is
a pulper vessel.
In a further embodiment, the aqueous solution has
a substantially neutral or alkaline pH, the latter
including a pH of at least 9.S.
In still another embodiment, the fraction
separated from the surface of the aqueous solution is
washed to separate cellulosic fibres from said fraction,
the cellulosic fibres being optionally combined with the
aqueous solution from the vessel.
In another embodiment, solution passing from the
vessel is passed to a screen having a mesh size to effect
separation of thermoplastic polymer and metallic foil from
cellulosic fibres, solution with cellulosic fibres passing
through the screen, and then subjected to at least two
hydrocyclone cleaners, the first of said hydrocyclone
cleaners being adapted for rejection of material heavier
than cellulosic fibres and the second of the hydrocyclone
cleaners being adapted for rejection of material lighter
than cellulosic fibres.
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In a further embodiment, the solution is alkaline
and contains potassium hydroxide and/or sodium hydroxide.
In a still further embodiment, the foil is
aluminum foil.
S DETAILED DESCRIPTION OF THE INVENTION
The present invention is illustrated by the
embodiments shown in the drawings, in which:
Fig. 1 is a schematic representation of the
process of the invention;
Fig. 2 is a schematic representation of a process
utilizing the process of the invention; and
Fig. 3A and 3B are schematic representations of
scoops for the bucket conveyer.
The present invention is generally described
lS herein with reference to the metallic foil being aluminum
foil. Other metallic foils may be used.
In the embodiment of the invention illustrated in
Fig. 1, the process is generally indicated by 1. Vessel 2
contains aqueous solution 3 that is stirred by stirrer 4.
Paper product is fed to aqueous solution 3 through feed
inlet 5.
A bucket conveyer, generally indicated by 6, has
conveyer belt 7 passing around upper drive wheel 8 and
lower drive wheel 9. Conveyer belt 7 has a plurality of
scoops 10 located thereon. Conveyer 6 is located so that
scoops 10 pass beneath surface 11 of aqueous solution 3 in
vessel 2, for removal of material therefrom. Scoops 10
would normally be fabricated to retain thermoplastic
polymer and/or metallic foil components but pass aqueous
solution and cellulosic fibres.
In particular, the scoops 10 of bucket conveyer
6 may be in the form of a bucket with orifices or mesh in
the bottom thereof, with the size of the orifices or mesh
being large e.g. at least about 2.5 cm in size and
especially in the range of about 2.5-6 cm in size.
Alternatively, the scoops of the bucket conveyer may be in
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the form of tynes. Although a single tyne could be used in
some circumstances, at least two tynes should be used and
especially 3-6 tynes. Such tynes may be spaced apart by at
least 2.5 cm and especially 2.5-6 cm. Other shapes of
scoops may be used. Tynes are preferred. It is understood
that the pieces of thermoplastic polymer and/or metallic
foil that are removed with the bucket conveyer may be
relatively large e.g. have dimensions of several
centimeters in one or more directions, and it is intended
that the bucket conveyer remove at least a substantial
proportion of such pieces from pulper vessel 2.
Upper drive 8 of bucket conveyer 6 is located
above transfer conveyer 12, such that material from scoops
10 of bucket conveyer 6 can fall onto the surface thereof.
Such material is indicated by 13. The discharge end 14 of
transfer conveyer 12 is located above wash vessel 15. Wash
vessel 15 has outlet 23 located in the upper section
thereof and fluid outlet 17 in the bottom. Water inlets 16
are located above wash vessel 15.
Outlet 18 in vessel 2 is connected by pipe 19 and
inlet 20 to vessel 21. Fluid outlet 22 passes fluid from
vessel 21.
In operation, paper product is fed through inlet
5 to vessel 2. The paper product may be in a comminuted
form, especially in a shredded form e.g. if the paper
product is absorbent sanitary paper product. In that
event, stirrer 8 is used to vigorously admix aqueous
solution 3. If the paper product is not in comminuted form
or if further comminution would be beneficial, stirrer 8
would be of a type that effects comminution of the paper
product e.g. vessel 2 could be a pulper and stirrer 8 could
be pulper knives. Vessel 2 is operated so that paper
product therein is in a form that permits removal of
thermoplastic polymer and/or metallic foil by the bucket
conveyer. Similarly, scoops 10 are cooperatively designed.
Bucket conveyer 6 is operated to remove
thermoplastic polymer and/or metallic foil from the surface
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of aqueous solution 3. The polymer and foil is then
deposited onto transfer conveyer 12 and subsequently into
wash vessel 15. The thermoplastic polymer and metallic
foil is washed in wash vessel 15, using water inlets 16,
especially to flush cellulosic fibre from the thermoplastic
polymer and foil. Aqueous solution and cellulosic fibre
passes from wash vessel 15 through outlet 17, and in the
embodiment shown is fed to vessel 21. Vessel 21 also
receives aqueous solution and cellulosic fibre from vessel
2 through transfer pipe 18. It is understood that aqueous
solution in vessel 21 will contain thermoplastic polymer
and metallic foil, especially such components in relatively
small particle size, received from both vessel 2 through
transfer pipe 19 and from wash vessel 15.
Solution passing from vessel 21 would normally be
subjected to further processing for recovery of components
therein, especially cellulosic fibres, for example using
the method discussed below. Thermoplastic polymer and
metallic foil passing from outlet 23 may be subjected to
further processing to separately recover the polymer and
metal.
Fig. 2 illustrates a method of treating
cellulosic fibre solution passing from vessel 21. Solution
is passed from vessel 21 through outlet 22 to first screen
vessel 24, which has coarse screen 25. On the upstream
side of coarse screen 25 is discharge outlet 26 for the
discharge of large particles i.e. particles not passing
through coarse screen 25, into bin 27. On the downstream
side of first screen vessel 24 is transfer line 28 for the
discharge of solution passing through coarse screen 25.
Transfer line 28 passes solution into the upstream of
second screen vessel 29. Second screen vessel 29 has a
discharge outlet 30 on the upstream side of fine screen 31
into bin 32 for particles that will not pass through fine
screen 31. The downstream side of fine screen 31 is
connected to transfer line 33.
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Transfer line 33 is connected to a hydrocyclone
cleaner that is referred to herein as a Posiflow cleaner
34, the discharge of heavy particles from Posiflow cleaner
34 occurs through discharge outlet 35. Solution with
lighter particles is discharged from Posiflow cleaner 34
through transfer line 36 to the inlet of a hydrocyclone
cleaner that is referred to herein as a Uniflow cleaner 37.
In operation of the embodiment of Fig. 2,
solution is continuously passed through transfer line 22
into first stream vessel 24, in which large particles of
thermoplastic material, usually essentially in the form of
thermoplastic film, and pieces of metallic foil are
separated as these are not passed through coarse screen 25.
These large particles would be particles that the bucket
conveyer has failed to scoop from the top of aqueous
solution 3. The mesh size of coarse screen 25 is selected
to effect such a separation. Cellulosic fibres and
solutions pass through coarse screen 25 and are transferred
into transfer line 28 into second screen vessel 29. Second
screen vessel 29 has the screen of a smaller mesh size than
that of first screen vessel 24. Further separation of
thermoplastic polymer and metallic foil particles is
effected in second screened vessel 29. Second screen
vessel 29 effects a separation of pieces of thermoplastic
film and metallic foil that were small enough to pass
through coarse screen 25. These particles of thermoplastic
film and metallic foil had discharged from the upstream
side of fine screen 31 into bin 32.
Cellulosic fibre and solution pass through fine
screen 31 and our transferred through transfer line 33 into
Posiflow cleaner 34. Posiflow cleaner 34 effects a
separation of dense particles from the solution, which are
discharged through discharge outlet 35. The bulk of the
solution, containing the cellulosic fibres is passed
through transfer line 36 to the inlet of Uniflow cleaner
37. Uniflow cleaner 37 effects a separation of low density
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particles from the solution, through discharge outlet 38.
Again the bulk of the solution passes through transfer line
39 into separator 40. Separator 40 effects a separation of
solution from cellulosic fibres. In a particular
embodiment, separator 40 is known as a dynamic washer,
which effects both separation of the cellulosic fibres and
the washing of those fibres, which are discharged through
upstream outlet 43.
Fig. 3A shows a section of a bucket conveyer,
lo having conveyer belt 60 with bucket 61 thereon. Bucket 61
is attached to conveyer belt 60 by bolts 62. Scoop 61 is
in the form of a bucket, having a base 63. Base 63 of
bucket 61 has a plurality of orifices 64. As discussed
herein, the orifices should have a diameter of at least
about 2.S cm and especially about 2.5-6 cm. ~hile Fig. 3A
shows a bucket with orifices in the bottom thereof, it is
understood that the bucket could have a mesh in the bottom
thereof.
Fig. 3B shows conveyer belt 60 having base plat
65 attached thereto by bolts 66. Base 65 has tynes 67
extending therefrom. In the embodiment shown in Fig. 3B,
four tynes 67 are shown, although the number of tynes could
be two or more, as discussed herein. Tynes 67 should be
spaced apart by at least about 2.5 cm and especially about
2.5-6 cm, as discussed herein.
The invention has been particularly described
herein the reference to the use of a bucket conveyer to
separate thermoplastic polymer and/or metallic foil from
the surface of the aqueous solution. While this is the
preferred method, other-skimming devices, weirs or baffles
could be used.
As discussed above, the paper product may be
coated paperboard. The paperboard is coated on a least one
side with at least one of thermoplastic polymer and
metallic foil. The thickness of the paperboard will vary
depending on the particular end use of the coated
paperboard. However, in the beverage and juice packaging
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industries, typical thicknesses are in the range of about
175 to about 450 g/m. The thermoplastic polymer coating
will normally be a heat sealable coating, at least the
outer coating will normally be heat sealable for ease of
fabrication of the beverage or juice container. Such
coatings may be a polyolefin e.g. polyethylene,
polypropylene, ethylene copolymers e.g. ethylene/vinyl
acetate copolymers and the like, and would comply with
health and other regulations for packaging of foodstuffs.
The metallic foil is normally used as a barrier layer, and
be interposed between layers of the thermoplastic polymer,
or between thermoplastic polymer and a layer for the
bonding of the foil to the cellulosic layer i.e. the
paperboard. The metallic foil will usually be aluminum
foil.
Another example of the paper product is absorbent
sanitary paper product. Examples of the construction of
such product has been described above.
The process may be operated with the aqueous
solution in vessel 2 at substantially neutral pH or at
alkaline pH. The pH of solutions in subsequent steps in
the process will generally tend towards a neutral pH, due
to washing procedures or addition of water. Substantially
neutral pH is intended to mean the pH obtained by use of
~5 municipal water, or other similar water, which will likely
to be at a slightly acidic pH in the pulper due to residual
amounts of liquid in the coated paperboard especially where
the coated paperboard is in the form of juice boxes which
can contain residual amounts of e.g. orange juice.
Substantially neutral pH is preferred, especially for
economic and environmental reasons. Alkaline pH's may be
used, including a pH of at least 9.5, and preferably at
least 10. This solution is preferably formed from an
alkali metallic hydroxide, especially sodium and/or
potassium hydroxides. Sodium hydroxide is preferred.
Techniques for removal of SAP from processes of
the type described herein have been described in the
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aforementioned PCT application of M.E. Conway et al. Such
techniques may be embodied in the aqueous solution used
herein.
In its overall context, the present invention will
permit a recycling system that would involve the collection
of paper products, especially in the form of beverage
boxes, disposable diapers, incontinence products and
feminine hygiene products, and the like after use, in
thermoplastic bags or other suitable collection containers,
including a polyethylene bag, from households, institutions,
hotels and the like. The paper products would then be
transported to a processing facility for treatment according
to the process of the present invention.
Cellulosic material obtained from the process of the
invention is relatively un-degraded and un-refined material,
compared to cellulosic material that has been subjected to
processes for the manufacture of paper, tissue or towelling.
In addition, the cellulosic material may be cleaner, i.e.
whiter, than cellulosic material obtainable from many other
sources. It has potential for use in a wide variety of end
uses, including recycling back into diaper and beverage box
manufacturing processes. Many of the solutions used in the
process may be treated for recovery of components, reused in
the process, or in other processes. For example, the alkali
metallic hydroxide solution may be recycled from separator
40 back into pulper vessel 2.
The hydrocyclone cleaners referred to above have been
described with respect to Fig. 2 as being Posiflow cleaners
34 and Uniflow cleaner 37, both of which are obtainable from
the Beloit Jones Division of Beloit Corporation, Dalton,
Mass., U.S.A.. The former type of hydrocyclone cleaner
effects removal of heavy particulate matter and the latter
effects removal of lighter particulate matter. It is
understood that a plurality of hydrocyclone cleaners may be
used, both of the Posiflow
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cleaner type and of the Uniflow cleaner type. Each type of
hydrocyclone cleaner may be used in parallel with similar
hydrocyclone cleaners and/or in series with similar
hydrocyclone cleaners in order to more effectively separate
heavy and light matter.
It is understood that vessels may be inserted
into any stage of the process in order to control the rate
of flow of solution through the process. This is likely to
be particularly important if any stage of the process is
operated in a batch mode.
The paper product fed to the aqueous solution may
be in a comminuted form. In particular, the paper product
may be shredded. However, if the paper product is in a
fine particle form, such particles would be more difficult
to remove using the bucket conveyer, thereby possibly
causing process complications in subsequent steps in the
process. Suitable selection of the buckets of bucket
conveyers can alleviate this potential problem. It is
preferred, if the coated paperboard is comminuted prior to
feeding to the solution, that the particles be relatively
large to facilitate removal either on the first screen or
more preferably using the bucket conveyer as described
above.
In an embodiment of the invention, the paper
product is fed to the aqueous solution without being
comminuted, with the first vessel then being in the form of
a pulper equipped with rotating knives to effect the
breakdown of the paper product into smaller pieces. Such
a use of a pulper has been found to be a useful way of
obtaining the paper product, especially coated paperboard
in a suitable size to effect the separations described
herein.
~ r; ~i ng should not be so vigorous as to cause
thermoplastic polymer and metallic foil pieces to be pulled
down from the surface of the vessel into the bulk of the
solution, thereby making separation using a bucket conveyer
more difficult.
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It is possible to increase the amount of paper
product in the aqueous solution to an extent such that on
pulping or agitation, the particles of thermoplastic
polymer and metallic foil become immersed within the
solution in a relatively uniform manner. If the amount of
paper product in the aqueous solution is reduced, the
thermoplastic polymer and metallic foil tends to accumulate
at the top of the aqueous solution, thereby facilitating
removal. It is preferred that the process be operated such
that there are some natural separation of cellulosic fibres
and from the less dense thermoplastic polymer and metallic
foil in the aqueous solution. The use of the lower
concentrations will also facilitate subsequent processing
of the materials.
It is preferred that the pulped solution contain
3-12% pulp, sometimes referred to herein as a consistency
of 3-12%, more preferably 3-10% pulp and especially 5-6%
pulp. The actual apparatus used will have an effect on the
preferred consistency. In addition, the pulping should be
operated such that the amount of film and aluminum foil fed
to the hydrocylones, as described herein, is not more than
10% of the amount of cellulosic fibres, especially not more
than 7% by weight. Preferred amounts are 4-6% by weight.
The composition of the pulp will depend on the
nature of the coated paperboard fed to the process. ~or
instance, if the coated paperboard is juice boxes, the pulp
may contain about 55% cellulosic fibre, about 40% plastic
and 5% aluminum. Other coated paperboard will have
different amounts of cellulosic fibre, plastic and
aluminum. Some coated paperboard will not contain aluminum
or other metallic foil. The ratio of cellulosic fibre to
plastic may vary over a wide range. Such wide variations
in the ratio of cellulosic fibre : plastic : aluminum foil
are acceptable, and the ratio in an operating process is
likely to vary considerably with time, depending on the
origin of the feedstock.
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In an embodiment of the present invention,
especially when printed products are fed to the process,
the solution is subjected to one or more steps to remove
ink. This may be accomplished using a pressurized de-
inking module, which is obtainable from the Beloit JonesDivision of Beloit Corporation, Dalton, Mass., U.S.A.
Such a pressurized de-inking module would normally be
inserted in the process subsequent to the screen used to
separate fine particulate matter. One or more
pressurized de-inking modules may be used. Such a use of
a pressurized de-inking module will result in the
production of cellulosic fibres of improved colour,
particularly when the paper product contains ink.
In embodiments of the invention, the first screen in
the process has a mesh size in the range of 0.025-0.055
inches (0.064-0.14 cm), especially in the range of 0.035-
0.045 inches (0.089-0.11 cm). It is preferred that any
second screen in the process has a mesh size in the range
of 0.006-0.012 inches (0.015-0.030 cm).
Although the first screen may be used for separation
- of thermoplastic polymer and metallic foil of relatively
large size, such separation is secondary to that of the
bucket conveyor, as described above.
The vessel shown is vessel 16 in Fig. 1 may be a
vessel of a type known as a trommel or used in
conjunction with a trommel. Such vessels are used to
accomplish both separation and washing of the material
passing through the vessel.
It is to be understood that immediately prior to
separator 40, shown in Fig. 2, the cellulosic fibres may
be subjected to steps for brightening, washing and/or
treatment with disinfectant in order to improve the
quality of the product being obtained and/or to meet
various governmental regulations. If the metallic foil
component is aluminum, which is commonly used in
packaging, then the aluminum may be separated from
thermoplastic polymer using, for example, alkaline
A~E~G~S~rT
CA 02207963 1997-06-16
solutions. Alternatively, the polymer could be burnt off
the foil. The thermoplastic material, which is normally
a polyolefin, may be used in a variety of end uses.
The present invention is illustrated by the
following examples:
EXAMPLE I
Beverage boxes were received from institutions.
These boxes contained straws and unconsumed juices. The
boxes were fed to a pulper and pulped in aqueous solution
for about 30 minutes. The pulping was carried out in a
manner such that pieces of thermoplastic polymer and
metallic foil floated to the top of the solution. These
pieces were removed using a bucket conveyor, washed in a
trommel to remove free cellulosic fibres and then baled.
The bales contained approximately 93~ thermoplastic
polymer, 5~ aluminum foil and 2% cellulosic fibres. In
contrast, juice boxes typically contain about 20%
thermoplastic polymer, 5% aluminum foil and 75
cellulosic fibres.
The solution from the pulper was combined with the
cellulosic fibres from the trommel, and then subjected to
a coarse screen with a mesh size of 0.035 inches (0.089
cm) and then a fine screen with a mesh size of 0.006
inches (0.015 cm).
Solution passing through the fine screen was
subjected to a hydrocyclone to remove heavy particulate,
and then a pressurized de-inking module to remove ink and
other particulate. The solution was then subjected to
hydrocyclones to remove heavy and then lightweight
particulate matter, brightened and washed.
The cellulosic fibre separated from the process was
white and of good quality, suitable for recycling as
tissue-grade or fine paper-grade fibre.
EXAMPLE II
Approximately, 63,500 pounds (28,860 kg) of juice
boxes and milk cartons, being in the form of
polyethylene-coated cardboard or polyethylene and
r~i3"r,~ T
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aluminum foil-coated cardboard, were fed to a process of
the invention. The juice boxes were fed in 28 separate
loads with an average weight of approximately 1300 pounds
(590 kg), and for these boxes a pulping time of 32
minutes was used. The milk cartons were fed in 19
separate loads at an average weight of 1260 pounds (570
kg) per load with an average pulping time of 49 minutes.
One further load of mixed juice boxes and milk cartons
weighing approximately 1300 pounds (590 kg) was also fed
to the process, with a pulp time of 30 minutes.
In all batches processed, the pulp consistency was
approximately 5-5.5% by weight of the aqueous solution.
The process was operated at substantially neutral pH i.e.
municipal water was used without addition of alkali. The
process was also operated at ambient temperature.
The boxes were pulped and processed using a process
of the type shown in Fig. 1. The knives used in the
pulper were of a type referred to herein as shark knives.
Solution passing from the pulper was subjected to a
course screen with a mesh size of 0.035 inches (0.089 cm)
and then to a fine screen with a mesh size of 0.010
inches (0.025 cm).
Solution passing from the fine screen was subjected
to a pressurized de-inking module for removal of fine
particulate matter, including fine plastic material,
aluminum foil and ink. The solution was then subjected
to hydrocyclones to remove heavy and then lightweight
particulate matter, and then to brightening and washing
steps.
The cellulosic fibre separated from the process was
found, on visual inspection, to be white and of good
quality. Visual inspection also showed that plastic and
aluminum foil had been separated effectively from the
cellulosic fibre.
This example shows that the process is capable of
being operated on substantial quantities of juice boxes
and milk cartons.
