U.S. patent application number 11/393963 was filed with the patent office on 2007-10-04 for system and a method for extracting wax from pulp fibers and paper products.
Invention is credited to Roger O. Campbell.
Application Number | 20070227945 11/393963 |
Document ID | / |
Family ID | 38557243 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227945 |
Kind Code |
A1 |
Campbell; Roger O. |
October 4, 2007 |
System and a method for extracting wax from pulp fibers and paper
products
Abstract
A system and a method for extracting wax from pulp fibers
an-d/or paper products are provided. The system and method may
implement a continuous extraction vessel that can have one or more
extraction stages. A single or multi-staged continuous extractor
would provide solvent flow which counters the cellulosic materials
within the vessel so that the solvent becomes more concentrated
with the dissolved wax. This will reduce the volume of solvent
necessary to achieve the same extraction efficiency and reduce the
energy necessary to remove the solvent from the wax. In another
embodiment, the temperature of the solvent can be increased by
operating the extractor under a pressure greater than atmospheric
pressure.
Inventors: |
Campbell; Roger O.; (Auburn,
WA) |
Correspondence
Address: |
WEYERHAEUSER COMPANY;INTELLECTUAL PROPERTY DEPT., CH 1J27
P.O. BOX 9777
FEDERAL WAY
WA
98063
US
|
Family ID: |
38557243 |
Appl. No.: |
11/393963 |
Filed: |
March 30, 2006 |
Current U.S.
Class: |
208/33 |
Current CPC
Class: |
Y02W 30/648 20150501;
D21C 5/02 20130101; C10G 73/06 20130101; Y02W 30/64 20150501 |
Class at
Publication: |
208/033 |
International
Class: |
C10G 73/06 20060101
C10G073/06 |
Claims
1. A system for performing an extraction of wax from secondary
fiber comprising: an extractor; a supply of secondary fiber
delivered to the extractor; and a supply of solvent delivered to
the extractor wherein wax contained within the secondary fiber is
soluble in the solvent; wherein a pressure within the extractor is
greater than atmospheric pressure and sufficient to raise a
temperature of the solvent beyond the boiling point of the
solvent.
2. The system of claim 1 wherein the extractor is a continuous
extractor.
3. The system of claim 1 wherein a time period for the extraction
is in a range from about 5 minutes to about 30 minutes.
4. The system of claim 1 wherein the solvent is hexane.
5. The system of claim 1 further comprising: a system for
separating the wax from the solvent.
6. The system of claim 1 further comprising: a system for drying
the secondary fiber after the extraction.
7. The system of claim 1 wherein the temperature of the solvent is
greater than 50 degrees Celsius.
8. A method for performing an extraction of wax from secondary
fiber, the method comprising the steps of: supplying the secondary
fiber to an extractor wherein the secondary fiber contains wax; and
supplying solvent to the extractor wherein the wax contained within
the secondary fiber is soluble in the solvent; wherein a pressure
within the extractor is greater than atmospheric pressure and
sufficient to raise a temperature of the solvent beyond the boiling
point of the solvent.
9. The method of claim 8 further comprising the step of: separating
the solvent from the wax.
10. The method of claim 9 further comprising the step of: recycling
the solvent to the extractor.
11. The method of claim 8 further comprising the step of: drying
the secondary fiber after the extraction.
12. The method of claim 11 further comprising the step of:
re-pulping the secondary fiber.
13. The method of claim 8 wherein the solvent is hexane.
14. The method of claim 8 wherein the temperature of the solvent is
greater than 50 degrees Celsius.
15. The method of claim 8 wherein the extraction occurs in a range
from about 5 minutes to about 30 minutes.
16. The method of claim 8 wherein the secondary fiber is pre-heated
before the extraction.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to a system and a method
for extracting wax from pulp fibers and paper products.
BACKGROUND OF THE INVENTION
[0002] The ability to recycle Wax Saturated or Curtain Coated old
corrugated containerboard ("OCC") has implications for current and
future markets, product quality and manufacturing costs. One
approach that was recommended comes from earlier work on the
solvent extraction of wood chips..sup.1 In this work, a method was
developed to remove pitch and wood extractives before processing in
the pulp mill. A similar process could remove wax from fiber
products. The result is that low wax content fibers are recovered
and used through a normal OCC process. This process recovers the
wax as a product for reuse in the box plants or sold for other
uses. The result is nearly all of the WOCC.sup.2 box material is
processed into economic products and there are minimal losses or
environmental impacts. .sup.1U.S. Pat. Nos. 5,698,667; 6,364,999;
6,641,699 and 6,719,880 .sup.2WOCC means Wax coated or saturated
OCC.
[0003] The concept of removing extractives with organic solvents is
known. The paraffin wax used in WOCC is very soluble in a number of
organic solvents. U.S. Pat. No. 5,891,303 describes the use of
Hexane for the removal of paraffin waxes from recycled fiber
products. A report.sup.3 has been found that describes a similar
approach in other paper products. .sup.3Miyagi, Atsushi and
Ishiwata, Yasuyuki; Ind. Res. Inst. Chiba Prefect., Japan, 264;
Chiba-ken Industrial Laboratory Research Report No. 8 (1994).
[0004] The problem of recycling wax saturated and coated boxes is
that small amounts of residual contaminates can have large impacts
on product quality. Methods of dispersion and surfactant washing
produces a pulp that can have strength reductions of as high as 20%
with less than 1% wax contamination. However, the wax contamination
is much higher than 1% from these processes. Other disadvantages
are process management, cost of removal, and treating of the
process water to maintain productivity and environmental
requirements. Both the mechanical and dispersive methods are prone
to incomplete removal and process contamination.
[0005] The approach in which wax is dissolved and washed away has
the advantage of minimizing the cross-contamination with, for
example, the paper mill process water and presents the opportunity
to recover the wax as a potential product for sale or reuse within
the box making system. The environmental impacts are minimal and
can be managed within the confine of the extraction process.
[0006] Two other approaches have been discussed in the
literature.sup.4 and they include removal under supercritical
conditions using CO.sub.2 or a combination of CO.sub.2 and a
hydrocarbon solvent like Pentane.sup.5. The advantage of this
method is that the solvent can be easily removed and the wax
recovered as a product. The disadvantage is the high energy and
equipment cost of working at supercritical conditions. The other
dissolving method is to use a solvent that can dissolve and remove
the wax under or near ambient conditions. For example, U.S. Pat.
No. 5,891,303 describes a method for Hexane removal of wax from
waste paper and container products. The patent describes an
extraction time of 20 to 60 minutes, repeated 3 to 5 times. This
would require a minimum of 60 minutes to a maximum of 5 hours to
extract the wax. The process as described would represent a very
capital and labor intensive operation. In addition, the
environmental impacts of opening the extraction vessel would not
permit the process to be commercialized. The method of only heating
the solvent to approximately 45.degree. C. to 50.degree. C. may
cause the extraction to take a substantially large amount of time,
and increases the number of extraction cycles, as well as increases
the amount of solvent required. .sup.4U.S. Pat. No. 5,009,746, S.
U. Hossain and C. A. Blaney, Removal of stickies from secondary
fibers using supercritical carbon dioxide solvent. .sup.5Study of
co-solvent effects on stickies removal. Part 1: supercritical fluid
extraction; Rong X; Qi D; Chateauneuf J; Abubakr S, 2005 Practical
Papermaking Conference, Milwaukee, Wis., USA, May 2005, Session 8,
13 pp.
[0007] A need, therefore, exists for an improved system and method
for wax removal from a paper product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The embodiments of the present invention are described in
detail below with reference to the following drawings.
[0009] FIG. 1 is a diagram of a system for wax removal in an
embodiment of the present invention;
[0010] FIG. 2 is a chart of the percentage of wax removal versus
the number of extraction stages via one of the methods of the
present invention; and
[0011] FIG. 3 is a chart of a weight-time curve based on wax
removal in an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention generally relates to a system and a
method for extracting wax from pulp fibers and paper products. The
system and method can be designed in a number of ways. The design
and operating conditions will change as the temperature is
increased. Some embodiments would include a process that operates
at ambient conditions, or a process that operates at elevated
temperatures and pressures. The system and method may implement a
continuous extraction vessel that can have one or more extraction
stages. A single or multi-staged continuous extractor would provide
solvent flow which counters the cellulosic materials within the
vessel so that the solvent of the miscella becomes more
concentrated with the dissolved wax. This will reduce the volume of
solvent necessary to achieve the same extraction efficiency and
reduce the energy necessary to remove the solvent from the wax. In
an embodiment, the solvent is Hexane. However, other solvents are
effective in dissolving wax. In an embodiment, the wax-solvent
solution is sent to a system for separating the wax from the
solvent. The solvent is then recycled back to the extractor. In an
embodiment, the fiber is sent to a system for drying and possibly
re-pulping. The extracted OCC can be, for example, rebated for
shipment, or the fibers can be conveyed directly to an OCC repulper
and a papermachine.
[0013] In an embodiment, the extraction process may be performed in
a range from approximately five minutes to approximately 30
minutes. The operating temperature range would be approximately
60.degree. C. or higher. The total amount of solvent required for
this process would be a ratio of approximately 4 to 1 or less based
on the bone dry cellulosic material weights. This reduction in
solvent will significantly reduce energy requirements.
[0014] In the case where a process is operated at or near
atmospheric conditions, the temperature may be limited to the
boiling point of the solvent. In the case described using Hexane,
operating temperature would be around 69.degree. C. With the
ambient conditions, the system would be closed to the atmosphere
and a slight vacuum applied to maintain a closed system. All
internal gases in the process are recovered and condensed with
final exhaust gases passing through a carbon filter to remove
VOC's.sup.6 before final discharge. .sup.6VOC means Volatile
Organic Compound.
[0015] In another embodiment in which pressure is increased, the
pressure within the extractor may be set to a pressure sufficient
to raise the temperature of the solvent beyond the boiling point of
the solvent at ambient conditions but maintain the solvent in the
liquid state..sup.7 It should be understood that the extraction
vessel described herein should be capable of operation at pressures
above atmospheric and the pressure would be limited only by the
design of the extraction vessel and operating economics. In another
embodiment, the temperature of the solvent can be increased by
operating the extractor under some pressure greater than
atmospheric pressure. The higher temperature and pressure would
increase the diffusion rates of the solvent and solubility of wax.
This system and process would also allow for significantly lower
extraction time and less amount of solvent required to perform the
extraction. .sup.7 Ambient conditions assumes a pressure of 760
mmHg.
[0016] Referring to FIG. 1, in a first step of the process,
secondary fiber products 2 containing wax, are delivered through a
shredder 4 to reduce size for optimum handling. The products 2 may
be, for example, old corrugated containerboard ("OCC"). Secondary
fiber may be defined as fiber which has been dried at least once.
The OCC feedstock may be conveyed into a pre-heating vessel 6 prior
to delivery to an extractor 8. This may provide increased
extraction efficiency by increasing diffusion and dissolution
rates. In a next step, the feedstock is then conveyed into the
extractor 8 where the WOCC ("wax saturated old corrugated
containerboard") is heated and the solvent is added. In an
embodiment, the extractor 8 is a continuous extractor. In an
embodiment, the solvent is Hexane. Other solvents can be used and
the choice is dependent on the effectiveness and economics. For
example, some solvents which may be used include, but are not
limited to, aromatic and alkane hydrocarbon. In fact, any solvents
or any solvent that will effectively dissolve paraffin waxes and
coating blends is contemplated. The residence time in the extractor
would be about 15 minutes and the solvent is circulated in a
counter flow direction to improve the washing effect. The extractor
unit may have several stages or sections in which the solvent and
wax can drain and be pumped towards a previous section. For
example, the fresh solvent is introduced at the fiber discharge end
of the extractor and flows or is pumped between sections or
chambers until it is removed at the fiber addition end of the
extractor. There are several commercial vessels that can be used or
adapted to this process, and some of these are described further
below. In this way, the solvent and wax is flowing in the counter
direction to the containerboard. As the solvent removes the wax
from the containerboard, the solution (commonly referred to as
"miscella" in the industry) will get more concentrated as it moves
toward the extractor inlet. This is where the miscella is removed
from the vessel 10. The solvent and wax blend is accumulated into a
tank 14 that feeds the wax separation process. It can be filtered
to remove any solid debris at this point. At the discharge of the
extraction vessel, the free solvent is separated from the fibers by
gravity, represented by box/vessel 10. The fiber is then put
through a dryer 12 to recover the Hexane, or the solvent, for
reuse.
[0017] The wax-solvent solution is sent to a system having a
distillation process 15 to recover and separate the Hexane and
concentrate the wax as a product. More specifically, the wax may be
purified 9 after the separation 15 to provide the end product 11.
The fiber may be sent to a system for drying the fiber. After
drying the extracted OCC, may be, for example, baled 18 for
transport 20, or rewet with water. The fiber contains less than 1%
residual wax and could be used, for example, as a feedstock for an
OCC liner process. The wax may be in a condition for resale or may
be further processed for use in, for example, box plants. The
extraction process is designed to minimize the loss of solvent. A
typical mill recovers 99.9% of the solvent. Final air treatment
would be through a carbon filter to remove any volatile organic
compounds ("VOC's").
[0018] Hexane has demonstrated an ability to avoid dissolving the
starches and adhesives used in manufacturing containers and
containerboard. Therefore, the wax product is free of such
contaminates and can be economically processed for resale or reuse.
Wax contamination in some cases has been estimated to be around 3%
on average from OCC sources. This has a significant impact on
product quality and process costs. As a result, this process would
cause a significant reduction of wax entering, for example, a paper
mill. The operating and environmental impacts of wax removal to the
paper mill would be to reduce chemical requirements such as, for
example, defoamers and strength additives. This would reduce the
BOD and COD.sup.8 in the mill effluent system and could allow for
increase close-up of the mill. .sup.8BOD is Biological Oxygen
Demand and COD is Chemical Oxygen Demand both are indications of
water quality.
[0019] Referring again to FIG. 1, the Wax OCC 2 may be wax
impregnated OCC and is indicative of the receiving and
storage/supply process step in the system. This would be bale
handling and process feed equipment. The equipment used for
shredding cellulosic feed materials may be of the type appropriate
to reduce the size for efficient extraction of wax and movement in
an extractor.
[0020] With respect to the pre-heating step 6, this can occur
within an atmospheric or pressurized vessel used to get the wax and
OCC up to extraction temperatures. Several embodiments are possible
for this step and should not be limited to the following examples.
In a first embodiment, the feedstock is heated with direct steam
and the condensates are collected in container 7. When these are
cooled the wax is separated from the water phase and the
accumulated wax would be removed. In a second embodiment, a solvent
vapor is passed over the WOCC feed material allowing it to be a
heat sink and condense the vapor to a liquid. The solvent then
starts the process of dissolving and removing the wax. In other
embodiments, technologies such as ultrasonic, microwaves or
radiowaves might be adapted in this stage or the extractor stage to
enhance the process of mixing and solvent saturation of the feed
material.
[0021] Several commercially available extractors or digesters could
be adapted to this process. For example, in an embodiment, an
atmospheric extractor which may be implemented is one used in the
extraction of seed oils. This extractor is available through Crown
Ironwork, Inc., [Minneapolis, Minn.]. The extractor has multiple
stages with counter flow of the solvent. Models are available that
can remove wax through percolation washing of the samples or
immersion of the samples. These units are designed to operate at
atmospheric or slight vacuum conditions up to the boiling point of
the solvent.
[0022] Examples of pressure digesters that can be adapted to
extract wax are the PANDIA by GL&V of Canada--a horizontal
vessel design (usually inclined about 5 degrees) to operate under
pressure. A large screw conveys the cellulosic material as solvent
is washed or sprayed onto the feedstock. It can be designed to
pulp, wash or solvent extract wax or other materials. Another
horizontal vessel would be the STAKE digester from Stake
Technologies, LTD., Norval, Ontario, Canada. Both are known in the
trade for their use in pulping of recycled fibers. A third pressure
vessel known in the pulping trade is the Messing-Durkee (M & D)
Digester current manufactured by Andritz. This is a cylindrical
vessel oriented at approximately 45 degrees. The cellulosic
material is introduced at the top and it is conveyed down the top
half of the vessel and back up through the lower half before being
discharged. The material would be passed through the solvent as it
moved through the vessel. The solvent would be introduce at the
discharge end of the vessel and allowed to counter-flow in the
vessel for removal at a point where the cellulosic material is
introduced to the vessel. In another embodiment, the method of
extraction would involve the Andritz Vertical IMPREGNATOR which is
designed to receive compressed chips from a screw press, typically
for chemi-thermo mechanical pulping applications; it can be adapted
for a solvent extraction or impregnation process.
[0023] At the very end of the extractor, or after the cellulosic
material has been discharged, a drainage zone is used to drain any
excess solvent. This is due to the fact that the fiber has seen the
purest solvent at the end of the extraction vessel before
discharge. At this point in the process, the OCC will be saturated
with solvent. The saturated fiber can be moved through a screw
press or into a continuous dryer to remove and recover the residual
solvent. A combination of these steps is also possible. After the
fiber product has reached complete dryness, or all the solvent has
been removed, the fiber product can be sent to a repulper 16 for
blending into a linerboard furnish or baled 18 for shipment 20 to
another location. The pulp slurry obtained from the repulper 16
would be pumped to a storage tank 21 and later may be blended with
other pulps or chemicals to produce paper products like liner on a
papermachine.
[0024] The miscella is distilled to recover the solvent for recycle
to the extractor. The distillation equipment may be a solvent
stripper, but other forms of solvent removal are possible. Vacuum
distillation would reduce stripper temperature but may be limited
by the melting point of the wax. The solvent would be condensed and
flow to a storage tank 22. Typically, the process can be designed
to recover 99.9% of the solvent. The process will have an air
management system for the complete removal of solvent from all
process air streams. The final air treatment would be through a
carbon filter to remove any VOC's. The wax product is removed from
this stage as the distillation bottoms. The concentrated wax is
further purified, if necessary. With respect to wax purification,
wax, while it is still in liquid form, can be filtered and/or
bleached to remove contaminates and color. It would then be cooled
and packaged for delivery to, for example, a customer.
[0025] The present invention may be better understood by way of the
following examples:
EXAMPLE 1
[0026] The method to estimate the rate of wax removal was to
submerge a WOCC sample into a known volume of Hexane at its boiling
point (69.degree. C.). After a given amount of time, the sample was
removed from the solvent and allowed to drain and air dry. The
weight difference versus the time the sample was allowed to extract
would be used to calculate the extraction rate of the wax. The
total amount of wax was determined by a 24 hour Soxhlet extraction
with Hexane on a separate set of representative samples. Table 1
illustrates the total wax removal as a percentage of the total wax
available. This data is plotted in FIG. 2. TABLE-US-00001 TABLE 1
Wax Saturated OCC Extraction removal experiments Sample Wt. % wax
time, sec. weight, g Loss, g. Removed Temp. 69.degree. C. To 0
20.119 0 0 T1 120 15.514 4.605 74.9% T2 120 14.464 1.05 92.0% T3
120 14.125 0.339 97.5% T4 120 14.012 0.113 99.3% Final Wt. 13.97 %
Total Wax 30.6%
EXAMPLE 2
[0027] A series of extractions were run in which the solvent to
fiber ratio was changed to determine the optimum solvent volume. As
can be seen in Table 2, the earlier stage extractions are improved
with higher solvent ratios. However, within experimental conditions
it does not appear that a ratio above 4 is required. These
extractions were run at 69.degree. C. for 120 seconds as described
earlier. To test the impact of time, an extraction was done in 180
second periods instead of 120 second periods. In the last column of
Table 2, a significant difference is seen in the extraction
efficiency by this slight increase in time. Again, these tests were
run at 69.degree. C. Based on these results, it appears that a 4 or
5 stage extraction process would not require more than 12 to 15
minutes. TABLE-US-00002 TABLE 2 Extraction Efficiency vs Solvent
Ration and Time 4 to 1 @ Extract # 3 to 1 4 to 1 5 to 1 180 secs 1
49.4% 58.7% 57.5% 70.0% 2 74.7% 82.8% 82.1% 89.5% 3 88.6% 91.8%
91.7% 96.0% 4 93.9% 94.8% 95.7% 98.0% 5 96.3% 96.1% 97.8% 98.8%
[0028] The addition of pressure and temperature would improve these
response times and extraction efficiencies.
EXAMPLE 3
[0029] A series of extractions were run on Wax OCC samples in which
the solvent was recycled each time. The concentration of wax in the
solvent was allowed to increase in order to determine the
extraction curve. The extractions were carried out at approximately
69.degree. C., the boiling point of Hexane. The extraction
treatment was run for only 180 seconds. For each cycle a new sample
was used. The solvent ratio was determined on a weight basis of
solvent to sample. For example, for an OCC sample weight of 100
grams, 400 grams of solvent was used. This gives a 4 to 1 solvent
ratio. In the OCC samples, wax accounts for 36.7% by weight
percentage. The last column in the table is an estimate of the wax
remaining in the sample after each stage of an extraction. It
appears that a 3 stage extractor may be all that is needed. The
following table, Table 3, shows the data for saturated boxes:
TABLE-US-00003 TABLE 3 Wax Saturated OCC % Wax % wax % Wax removed
remaining in Extraction Conc. In this the OCC cycle Hexane cycle
sample 1 5% 80% 20% 2 9% 75% 5% 3 16% 72% 1% 4 21% 60% 1% 5 27% 49%
<1%
EXAMPLE 4
[0030] A similar set of experiments were run on a product having
curtain coated wax, i.e., a lower wax weight and formulation. The
results are shown in Table 4: TABLE-US-00004 TABLE 4 Wax Curtain
Coated OCC Cumulative wax removal Test Weyco Crown BC Extraction
69.degree. C. 69.degree. C. Temperature 1 35% 39% 2 70% 75% 3 86%
93% 4 94% 99% 5 99% 100%
[0031] The samples used in this example had a wax weight percentage
of 13%. In order to estimate the rate of wax extraction, a series
of extractions were done at the boiling point of Hexane (69.degree.
C.). The actual process temperature could be higher in a
pressurized process. Samples were placed into boiling Hexane for 2
minute periods. After each 2 minute period, the solvent was removed
and the amount of wax was determined. The Hexane extraction was
repeated using a new volume of solvent for each stage and the
amount of wax removed was determined. The wax removed after several
extractions were added together to arrive at the total removal
efficiency. The results are shown in the FIG. 3 and show nearly
100% of wax can be removed in a 4 stage extractor. For all of these
extractions, the solvent ratio averaged 3.8 to 1 and the
temperature was 69.degree. C. The determination of total wax in the
board was done by a 24 hr. Soxhlet extraction with Hexane. This
value was then used as the denominator for calculating the
percentage of wax removed.
[0032] The following example was directed to a system in which the
extractor 8 is operated at greater than atmospheric pressure:
EXAMPLE 5
[0033] A series of experiments were run with saturated and curtain
coated OCC samples at elevated temperatures to show the impact on
extraction efficiency. The procedure was to seal a sample in a
calorimetry bomb with a measured amount of solvent. A screen was
inserted in the container so the sample could be separated from the
Hexane solvent at the end of the extraction period. This sample and
vessel was suspended in an oil bath at 100.degree. C. The sample
and solvent were allowed to heat and sit in the oil bath for 120
seconds. At that time, the vessel was removed from the oil bath and
inverted. This was done to drain the miscella through a condenser
to capture the wax and reduce the pressure in the vessel. The
amount of wax removed was determined and the extraction efficiency
was calculated based on the total wax as determined by a Soxhlet
extraction on a separate sample. Based on these results, the number
of extraction stages and/or the solvent ratios can be reduced to
provide significant cost savings. In order to maintain maximum
liquid-solid contact, the pressure of the system is increased to
keep the solvent in the liquid state. TABLE-US-00005 TABLE 5 Wax
Extraction with Hexane at Elevated Temperatures Sample Wax Wax
Curtain Curtain Saturated Saturated Coated Coated Temperature
69.degree. C. 100.degree. C. 69.degree. C. 100.degree. C. Partial
766 1846 766 1846 Pressure mm Hg mm Hg mm Hg mm Hg of Hexane
1.sup.st 75% 93% 37% 59% Extraction, % wax removed 2.sup.nd 92%
>99% 70% 94% Extraction, % wax removed 3.sup.rd 98% >99% 90%
98% Extraction, % wax removed In all of these experiments the
extraction period was 120 seconds and the solvent ratio was 4 to
1.
[0034] The following is an example of the reduction in contaminates
resulting from solvent extractions.
EXAMPLE 6
[0035] Solvent extraction impacts on OCC contaminants known in the
paper industry as "stickies" were evaluated. Three sets of
handsheets were prepared and tested. These samples included an OCC
box material that had not been wax treated. This sample was
designated "Control OCC". The second sample was from the same
sample box material as the Control OCC sample, however this sample
was labeled "Wax OCC Unextracted". The third sample was from a wax
saturated box and was extracted with Hexane to remove at least 99%
of the wax. This sample was labeled "Extracted Wax OCC". Table 6
shows that the sample with wax has a higher contaminate level than
the Control OCC sample. The removal of the wax with Hexane can
reduce the contaminate level and reduce the variability.
TABLE-US-00006 TABLE 6 Waxed Box Extraction Study Stickies in OCC
Handsheets Results Control OCC 4.37 # of stickies per gram +/-0.8
Wax OCC Unextracted 5.61 # of stickies per gram +/-0.5 Extracted
Wax OCC 2.81 # of stickies per gram +/-0.2
EXAMPLE 7
[0036] Several samples of OCC (without wax) and WOCC were repulped
and made into handsheets. These were tested for typical Kraft Liner
properties. Kraft liner is typically known as a paper that is the
surface ply of a corrugated container box. The results are compared
in Table 7: TABLE-US-00007 TABLE 7 OCC and WOCC Handsheet testing
Gurley Mullen at STFI at Density Porosity 42# BW 42# Units
Kg/m{circumflex over ( )}3 Secs. Lbs. Lbs. in. Comments 1 Control
OCC 544.4 12.3 55 19.7 No WOCC, unused box 2 Control OCC/ 498.1
10.1 35 16.6 3.7% WOCC at 30% wax WOCC blend that would give a
final product wax of 0.15% 3 Recyled OCC 525.8 11.0 48 17.7 Mill
Sample 4 Extracted OCC 545.4 11.6 62 20.6 Hexane extracted 5 100%
WOCC 528.2 11.2 50 18.8 Hexane extracted only Extracted 0.1% wax
remained 6 OCC/WOCC 544.5 11.8 54 19.5 96/4% blend WOCC pulp Blend
(extracted) extracted
[0037] The Control OCC and WOCC samples were from box panels that
had not been used previous to testing. These provided a fair
comparison because they were from the same box plant and the same
production lot. The only difference is that one sample was treated
with wax. So, the comparison of sample #1 and the blended sample #2
is the amount of wax that is in the blend. As can be seen, this has
a significant impact on the OCC strength if the WOCC sample was not
treated to remove the wax. Sample #3 is from a typical OCC mill
with some contaminate control. It had better strengths than the
blend sample 2 but a lower strength than sample 1, the lab OCC
sample. The lab OCC sample #4 (no wax) was extracted with hexane
(one 2 min. extraction) and it shows an improvement in strength
over sample #1. This is mainly due to the removal of residual wood
extractive that are known to reduce bonding..sup.9 However, this
also points out that extraction with Hexane will not interfere with
the paper quality and bonding properties. .sup.9J. Brandal and A.
Lindheim, Pulp and Paper of Canada, October, 1968, T 431-435.
[0038] Sample #5 is the WOCC board that had been extracted several
times. It can be seen that a substantial portion of the original
strength properties have been recovered (Sample #1 vs. Sample #5).
It is not as great an amount as Sample #1 but is no worse than the
mill sample. Sample #6 is a blend of the Control OCC #1 and a 4%
blend of the extracted WOCC sample #5. This is a typical blended
level found in recovered OCC. As the data shows, the strength of
sample #6 is as good as the lab OCC sample #1 and better than the
mill sample #3. Based on this it can be inferred that most of the
original strength can be recovered with Hexane extraction of wax.
In addition, a typical blend of extracted WOCC and OCC will have
nearly the same quality.
[0039] While the embodiments of the invention have been illustrated
and described, as noted above, many changes can be made without
departing from the spirit and scope of the invention. Accordingly,
the scope of the invention is not limited by the disclosure of the
embodiments. Instead, the invention should be determined entirely
by reference to the claims that follow.
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