U.S. patent application number 10/164027 was filed with the patent office on 2002-12-12 for styrene copolymers in de-inking.
This patent application is currently assigned to Huntsman Petrochemical Corporation. Invention is credited to Hengst, Charles W., Nguyen, Duy T..
Application Number | 20020187905 10/164027 |
Document ID | / |
Family ID | 25076554 |
Filed Date | 2002-12-12 |
United States Patent
Application |
20020187905 |
Kind Code |
A1 |
Nguyen, Duy T. ; et
al. |
December 12, 2002 |
Styrene copolymers in de-inking
Abstract
Provided herein are compositions of matter useful in de-inking
secondary fibers. A composition according to the invention includes
an aqueous solution of an anionic form of a styrene-methacrylic
acid copolymer. When a surfactant is used in combination with the
copolymers herein described in a de-inking operation, a synergy is
observed in that the combination of copolymer and surfactant
combination together yield a recycled fiber product having higher
brightness level and a lower effective residual ink concentration
than recycled fibers produced using either the copolymer or
surfactant alone in the same operation.
Inventors: |
Nguyen, Duy T.; (Austin,
TX) ; Hengst, Charles W.; (Austin, TX) |
Correspondence
Address: |
Russell R. Stolle
Huntsman Corporation
P.O. Box 15730
Austin
TX
78761
US
|
Assignee: |
Huntsman Petrochemical
Corporation
Austin
TX
|
Family ID: |
25076554 |
Appl. No.: |
10/164027 |
Filed: |
June 6, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10164027 |
Jun 6, 2002 |
|
|
|
09766480 |
Jan 19, 2001 |
|
|
|
Current U.S.
Class: |
510/174 ;
510/475 |
Current CPC
Class: |
Y02W 30/648 20150501;
D21C 5/027 20130101; Y02W 30/64 20150501 |
Class at
Publication: |
510/174 ;
510/475 |
International
Class: |
C11D 009/00; C11D
003/37 |
Claims
What is claimed is:
1) A process for removing ink, toners, and the like from
ink-bearing secondary fibers which comprises the steps of: a)
providing a composition which comprises: i) a water-soluble form of
a styrene-methacrylic acid copolymer; ii) a surfactant; and iii)
water, b) forming a fiber suspension by contacting secondary fibers
with said composition and maintaining such contact for an effective
amount of time to cause the ink on said secondary fibers to be
removed from said fibers; and c) removing ink from said suspension
by a method selected from the group consisting of: flotation and
washing.
2) A process for removing ink, toners, and the like from
ink-bearing secondary fibers which comprises the steps of: a)
providing a composition which comprises: i) an anionic form of a
styrene-methacrylic acid copolymer, said copolymer having a styrene
content of any value in the range of 10.00% to 40.00% by weight
based upon the total weight of the copolymer, and wherein said
copolymer has a molecular weight of any value in the range of 1,000
to 100,000; ii) a cation selected from the group consisting of:
alkali metal cations, alkaline earth metal cations, ammonium ions,
and alkyl-substituted ammonium ions; iii) a surfactant; and iv)
water; b) forming a fiber suspension by contacting secondary fibers
with said composition and maintaining such contact for an effective
amount of time to cause the ink on said secondary fibers to be
removed from said fibers; and c) removing the ink from said
suspension by a method selected from the group consisting of:
flotation and washing.
3) A process for removing ink, toners, and the like from
ink-bearing secondary fibers which comprises the steps of: a)
providing an aqueous solution of an anionic form of a copolymer of
styrene and methacrylic acid; b) forming a fiber suspension by
contacting secondary fibers with said aqueous solution and
maintaining such contact for an effective amount of time to cause
the ink on said secondary fibers to be removed from said fibers;
and c) removing ink from said suspension by a method selected from
the group consisting of: flotation and washing.
4) A process according to claim 3 wherein the styrene content of
said copolymer is in the range of between 10.00% and 40.00% by
weight based upon the total weight of the copolymer.
5) A process according to claim 3 wherein the amount of fibers
present is in the range of between 0.50 and 20.0% by weight based
upon the total weight of all of the water, copolymer, and fiber
present.
6) A process according to claim 3 wherein the pH is in the range of
between 4.0 and 12.0.
7) A process according to claim 3, wherein the temperature of the
suspension is any temperature in the range of between 40.degree. C.
and 90.degree. C.
8) A process according to claim 3, wherein said suspension further
includes a surfactant.
9) A process according to claim 8 wherein said surfactant is
selected from the group consisting of: anionic surfactants and
non-ionic surfactants.
10) A process according to claim 8 wherein the surfactant is a
non-ionic surfactant present in any amount between about 0.01% and
5.0% by weight based upon the weight of the fiber to be
de-inked.
11) A process according to claim 8 wherein the surfactant is an
alkoxylated oil.
12) A process according to claim 8 wherein the molecular structure
of said alkoxylated oil contains two different alkylene oxide
units.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This Application is a divisional application of U.S. patent
application Ser. No. 09/766,480 filed Jan. 19, 2001 which is
currently still pending.
FIELD OF THE INVENTION
[0002] This invention relates to compositions and methods useful
for removing ink from secondary fiber within an aqueous medium.
More particularly, it relates to the use of copolymers of styrene
and methacrylic acid as additive agents for aqueous media in which
de-inking of secondary fibers take place.
BACKGROUND
[0003] The advent of the recycling of large quantities paper in
recent times has provided many benefits, including reduced
de-forestation and the preservation of other resources.
[0004] As part of the recycling of paper fibers, which recycled
paper fibers are commonly referred to as "secondary fibers" by
those in the art, a key step is the removal of the ink which was
formerly bonded to the fibers from the earlier printing present on
the paper. For many years, paper was printed with oil-soluble inks
which were readily removed by well-established, conventional
de-inking procedures. In general terms, such procedures involve
mechanically pulping used paper in an aqueous medium which contains
surfactant(s), which causes removal of the ink from the paper
fibers. The ink may be subsequently removed by washing or
flotation.
[0005] Attendant with the increased amounts of the recycling of
paper have also been several advances in printing, most notably the
widespread use of the laser printer and other forms of
electrophotographic copying including such methods as "inkjet",
non-impact, and xerography. Papers printed in such processes pose
additional problems to the recycler which are not found in
recycling paper that was printed using oil-soluble or oil-based
inks. The additional problems arise from the use of binders in
these newer inks which are not found in the oil-soluble inks used
previously. Such binders are typically polymeric materials that are
thermally bonded to the paper. These types of binders are not
readily dispersed by common surfactants like alkylphenol
alkoxylates or alkylbenzene sulfonates. Thus, paper produced from
recycled paper having electrophotographic printing thereon
according to conventional de-inking methods is generally darker
than that recycled from paper printed with oil-based inks, because
of the much lessened degree of removal of the ink from the
substrate.
[0006] The present invention provides a copolymer material which is
useful in combination with surfactants employed in aqueous systems
for de-inking paper fibers which are to be recycled. The copolymers
of the invention function synergistically with various surfactants
and provide recycled fibers having characteristics substantially
similar to virgin fibers used in papermaking. Since the copolymers
used in the invention are more hydrophilic and more surface active
than those found in the prior art, fibers which are de-inked in
accordance with the teachings of the present invention do not
agglomerate ink particles but rather disperse and stabilize the ink
particles, thus minimizing their tendency to become re-deposited on
the fibers.
SUMMARY OF THE INVENTION
[0007] The present invention is directed at compositions of matter
useful in de-inking secondary fibers. A composition according to
the invention comprises an anionic form of a styrene-methacrylic
acid copolymer, in which the copolymer has a styrene content of any
value in the range of 10.00% to 40.00% by weight based upon the
total weight of the copolymer. The molecular weight of the
copolymer is preferably in the range of 1,000 to 100,000. To
maintain charge balance, a composition according to the invention
also includes a cation, which is preferably selected from the group
consisting of: alkali metal cations, alkaline earth metal cations,
ammonium ions, and alkyl-substituted ammonium ions, although any
cationic species which does not detract from the performance of a
composition in de-inking secondary fibers is a functional
equivalent to such cations. A composition according to the
invention may also comprise a surfactant, which may be cationic,
anionic, or non-ionic, with non-ionic surfactants being preferred.
A composition according to the invention also preferably comprises
water.
[0008] The invention also includes a process for removing ink,
toners, and the like from ink-bearing secondary fibers which
comprises first providing an aqueous solution of an anionic form of
a styrene-methacrylic acid copolymer, which preferably, though not
necessarily, contains a surfactant. A fiber suspension is formed by
contacting secondary fibers with said composition and maintaining
such contact for an effective amount of time to cause the ink on
said secondary fibers to be removed from said fibers. Finally, the
ink is removed from the suspension by a method which may include
flotation or washing.
DETAILED DESCRIPTION
[0009] The present invention relates to compositions useful for
removing inks from secondary fibers. Compositions according to the
invention comprise a water-soluble form of styrene-methacrylic acid
copolymer in which the copolymer has a styrene content between
about 10 and 40 percent by weight based upon the total weight of
the polymer. The preferred compositions according to the invention
are aqueous solutions of an alkali metal salt of a copolymer as
herein described. The copolymer can be used alone, or, more
preferably, in combination with an alkoxylated fatty alcohol and/or
an alkoxylated castor oil surfactant.
Styrene/Methacrylic Acid Copolymer and Water Soluble Salt
Thereof
[0010] The preparation of styrene/methacrylic acid copolymers is
straightforward and is known in the art. One method for preparing
such copolymers useful in the present invention involves fitting a
3-necked 1 L flange flask with a mechanical stirrer, heating
mantle, thermometer, reflux condenser, addition inlet, and
provision for maintaining an inert atmosphere within the reaction
vessel, such as a nitrogen inlet. The flask is charged with three
hundred thirty six (336) grams of isopropanol and one hundred
twelve (112) grams of water. Heating is commenced under stirring
and slow nitrogen sweep until a gentle reflux is achieved, at about
80 deg. Centigrade. A first stream comprising eighty (80)
milliliters of a 5% aqueous sodium persulphate solution was slowly
added to the contents of the refluxing contents of the flask
simultaneously with a second stream comprising a liquid mixture of
70.4 grams of styrene and 105.4 grams of methacrylic acid, over the
course of about 2 hours. Following the addition, the temperature
was maintained at reflux for an additional 2 hours to ensure
complete reaction. Then, an additional ten (10) milliliters of 22%
sodium persulphate was added, and the temperature maintained at
reflux for one additional hour to provide a styrene/methacrylic
acid copolymer.
[0011] To prepare a water-soluble salt of a copolymer produced as
per the above, namely the sodium salt, the flask from the above was
set up for distillation by affixing a head and condenser thereto.
The flask is heated until the azeotrope of isopropanol and water
begins to distill, and then two hundred thirteen (213) grams of a
23% (wt.) aqueous solution of sodium hydroxide is slowly added to
the flask during the distillation at a rate which is approximately
equal to the rate at which the azeotrope is being distilled. The
temperature of the contents of the flask are monitored, and when
the temperature reaches 100-105 deg., the flask is allowed to cool
to 50 degrees centigrade and the pH is adjusted to a level between
about 8 and 10 using aqueous NaOH, and to a total solids content of
between about 30 and 35% (wt.) as determined by evaporation of all
of the water from a sample of known weight and dividing the weight
of the solids remaining by the total initial weight and converting
to a percentage by multiplication by 100. This procedure affords an
aqueous solution comprising the sodium salt of styrene/methacrylic
acid copolymer, to which may be optionally added a surfactant in
order to provide a de-inking composition according to the
invention.
[0012] Although the water-soluble salt of the copolymer whose
preparation is described above as being the sodium salt as formed
by the addition of aqueous sodium hydroxide in the final step in
which the alcohol is removed by distillation, other basic
substances which produce a water-soluble polymer are suitable as
employment as neutralizing agents herein. Such basic substances
include without limitation alkaline aqueous solutions or
suspensions of other soluble metal cations, metal oxides,
carbonates, etc., including without limitation, basic carbonates of
any of the alkali metals, alkaline earth metals, monovalent iron,
the basic oxides of any of the alkali metals or monovalent iron,
ammonia, or alkyl-substituted amines including primary, secondary,
and tertiary amines provided that a solution of the copolymer
results after the admixture and heating. In cases where suspensions
of oxides are used, a longer heating time may be necessary to
effectuate solution, depending upon the particle size of the basic
substance.
[0013] In the above-described method for preparing a
styrene-methacrylic acid copolymer the styrene/methacrylic acid
ratio is about 40:60. Copolymers of styrene and methacrylic acid
having other ratios are also useful herein as the copolymer
component from which a de-inking composition according to the
present invention may be formed. The water-soluble forms of
copolymers of styrene-methacrylic acid having any content of
styrene in the range of 10.0% to 45.0%, by weight based upon the
total weight of the styrene-methacrylic acid polymer, including
every hundredth percentage therebetween, are suitable for use in
the present invention. These polymers having varied amounts of
styrene and methacrylic acid are made by altering the relative
amounts of each of the components in the second stream referred to
in the preparatory method above. For example, when a copolymer
having a styrene to methacrylic acid ratio of 30:70 is desired, the
second stream comprises 52.70 grams of styrene and 123.06 grams of
methacrylic acid. When a copolymer having a styrene to methacrylic
acid ratio of 20:80 is desired, the second stream comprises 31.15
grams of styrene and 140.61 grams of methacrylic acid.
[0014] The molecular weight of the copolymers produced according to
a procedure such as that described above in accordance with the
invention may be any molecular weight in the range of about 1,000
to about 100,000, with molecular weights having any value in the
range of 1,500 to 50,000 being preferred, and with molecular
weights having any value in the range of about 2,000 to about
30,000 being most preferred. The molecular weight of the final
copolymer is controlled by the concentration of the initiator and
the chain transfer agent, as is well known to those skilled in the
art of providing copolymers produced by this method. In the present
invention, the preferred chain transfer agent is isopropanol and
the preferred initiator is persulfate ion. Other functionally
equivalent chain transfer agents and initiators known to those
skilled in the art are useful in preparing the polymers described
herein.
The Surfactant Component
[0015] The present invention provides a compositions useful for
de-inking secondary fibers, which compositions comprise an aqueous
solution of a water-soluble form of a copolymer of styrene and
methacrylic acid described above. An aqueous composition according
to the present invention may also optionally include a surfactant.
Any surfactant is suitable for use as an optional ingredient for
inclusion in a composition according to the invention, including
anionic surfactants, non-ionic surfactants, and cationic
surfactants. Surfactants are well known in the chemical arts to
comprise a class of materials whose molecular structures include
both a hydrophilic portion and a hydrophobic portion. In addition,
a surfactant molecule as a whole may carry a positive charge,
negative charge, or may be electrically neutral, as is known to
those skilled in the art. The number and type of surfactants known
in the art is great indeed. It is most preferred that a surfactant
used in a composition according to the present invention is a
non-ionic surfactant. Alkoxylated oils are one class of non-ionic
surfactant which are produced by reacting an alkylene oxide with an
oil in the presence of a base catalyst, as such is well-known to
those skilled in the surfactant arts. Generally, to produce such
materials, one may use a tri-glyceride oil derived from any
vegetable or animal matter in combination with one or more alkylene
oxides. In cases where more than one alkylene oxide is used in the
alkoxylation of an oil, the molecular structure of the resulting
alkoxylated oil will contain two different alkylene oxide units. An
especially preferred non-ionic surfactant suitable for use in the
present invention is available from Huntsman Petrochemical
Corporation of Austin, Tex. under the designation "G-5000". The
amount of surfactant component present in a composition according
to the invention in any amount between 0.05% and 2.00% percent by
weight based upon the total weight of the fiber to be treated.
[0016] A de-inking solution according to the present invention may
be used at any temperature during its use between just above
freezing temperature to about 95 degrees centigrade, with about 25
degrees centigrade being preferred. The concentration of the
copolymer component in a de-inking solution according to the
present invention is preferably between 0.01% and 2.00% by weight
based upon the total weight of the dry fiber being de-inked. More
preferably, this amount is between 0.04% and 1.5%, with about 1.00%
being most preferable.
[0017] In order to de-ink a quantity of secondary fiber in
accordance with the present invention, one first provides an
sufficient water to contain the amount of the fiber to be treated.
Next, a water-soluble copolymer of styrene-methacrylic acid as
described above is added to the water and mixed to provide a
homogeneous solution of the copolymer in the water. This may be
done by adding the copolymer itself directly to the water and
mixing, or by adding an aqueous concentrate of the copolymer to the
water and mixing. Next, a water-soluble surfactant may be added,
and further mixing provided to yield a homogeneous solution to
which the fiber that is to be de-inked is subsequently added and
processed according to conventional methods. The examples given
below are illustrative of the present invention and of the synergy
discovered when using an alkoxylated fatty alcohol in combination
with the copolymers described herein. The following abbreviations
are used in the examples:
[0018] STYMMA 1--styrene methacrylic copolymer (30% styrene/70%
methacrylic acid, molecular weight 17,400).
[0019] STYMMA 2--styrene methacrylic copolymer (40% styrene/60%
methacrylic acid, molecular weight 12,500).
[0020] STYMAA 3--styrene methacrylic copolymer (50% styrene/50%
methacrylic acid, molecular weight 57,800).
[0021] STYMMA 4--styrene methacrylic copolymer (40% styrene/60%
methacrylic acid, molecular weight 22,700).
[0022] SURFONIC.RTM. L24-12--Ethoxylated linear alcohol.
[0023] CMC--Carboxyl Methyl Cellulose (available from Hercules,
Inc.)
EXAMPLE I
[0024] In a 4 oz. bottle were mixed 97.35 grams of tap water, 0.137
grams of 10% NaOH, and 2.0 grams of a 1% (as actives) aqueous
treatment solution, wherein the actives may be any of the STYMMA
copolymers, until homogeneous. Then 0.517 grams of blue security
envelope shreds were added to provide a slurry. This slurry was
stirred for 150 minutes at 60.degree. C., and a paper pad was made
by filtering the slurry through a small 5 cm 202 Reeve Angel filter
paper. The paper pad was air-dried, and the brightness and ERIC
(Effective Residual Ink Concentration) were measured using a
Technibrite Micro TB-1C instrument with ERIC 950 attachment,
available from Technidyne Corporation of New Albany, Ind. This
instrument adheres closely to appropriate Technical Association of
the Pulp and Paper Industry (TAPPI), ISO, and ASTM standards. The
purpose of ERIC is to determine how much ink remains in a sample of
fiber using infrared light. It is possible using light in the
infrared region to isolate ink optical effects for ink present at
ppm levels, other effects being invisible to IR light. The
brightness is read by a calibrated blue reflectance light beam.
Higher brightness and lower ERIC values indicate a more effective
treatment. Results of various samples prepared and tested in
accordance with this Example I using different STYMMA copolymers
above are shown in Table I below:
1TABLE I brightness and ERIC results on security envelope with blue
ink. Treatment Brightness ERIC, ppm Blank (untreated) 59.5 727
SURFONIC .RTM. L24-12 64.59 397 STYMAA 1 72.2 228 STYMMA 1/SURFONIC
.RTM. L24-12 (1:9 ratio) 77.9 78 STYMAA 2/SURFONIC .RTM. L24-12
(1:9 ratio) 77.8 85 STYMAA 3/SURFONIC .RTM. L24-12 (1:9 ratio) 73.8
223 STYMAA 4/SURFONIC .RTM. L24-12 (1:9 ratio) 75.7 176
[0025] The results clearly show that STYMMA 1 is more effective
than SURFONIC.RTM. L24-12, as evidenced by the higher brightness
value and lower ERIC value. However, it was unexpectedly found when
these two are blended that a synergy results, which provides higher
brightness values and lower ERIC values than either of the
components provide when used alone. Surprisingly, the blend of
STYMAA 1 and SURFONIC.RTM. L24-12 is far superior to that of STYMAA
3 and SURFONIC.RTM. L24-12.
EXAMPLE II
[0026] The secondary fiber used in this example was obtained from a
commercial paper mill. It consisted of 33.33% security envelope,
33.33% ledger stock, and 33.33% book print. The disintegrator was
used to furnish an aqueous pulp having a 5% consistency (5% by
weight of fiber with respect to the total weight of the pulp) by
adding 95 parts of water and 5 grams of fibers to the
disintegrator. The de-inking composition is also preferably added
to the disintegrator at this stage as well. The pulp is heated to
80.degree. C. for 30 minutes. After pulping, the stock was diluted
to about 1.7% consistency and was filtered through a #20 screen to
thicken the stock. The thick stock (about 15% consistency) was
diluted to 0.5% consistency, after which it was filtered again to
thicken the stock to about 15% consistency. The washing step was
repeated one more time. Finally, about 100 g was weighed out of the
diluted stock (0.5% consistency) and a paper pad was made using the
same filter paper as described in the Example I. The paper pad was
air-dried and brightness and ERIC were measured. Results are
reported in Table II:
2TABLE II brightness and ERIC results on mixed stock from
commercial paper mill. Treatment Dosage % Brightness ERIC, ppm
Untreated (blank) 0 62.9 410 SURFONIC .phi. L24-12 1 66.2 279 CMC 1
66.0 305 STYMAA 1 1 71.7 115 SURFONIC .RTM. L24-12 2 70.6 143
STYMAA 1 2 73.8 105 STYMAA 1 + SURFONIC .RTM. 2 74.3 90 L24-12 (1:9
ratio)
[0027] The Dosage % in table II is the amount of STYMMA copolymer
present by weight based upon the total weight of the fiber being
de-inked.
[0028] These results demonstrate that the use of a water-soluble
form of STYMAA 1 is by itself superior to conventional de-inker
surfactant, SURFONIC.RTM. L24-12, and conventional
anti-redeposition agent CMC. Again, a synergy was observed when
STYMAA 1 blended with SURFONIC.RTM. L24-12 was used as the
de-inking agent as evidenced by the higher brightness and lower
ERIC values.
[0029] It is preferred that solution according to the invention be
employed in a de-inking procedure be maintained at a pH level
between about 4.0 and 12.0. It is most preferred that the pH is
about 7.0-10.5. The pH may be adjusted as is known to those skilled
in the art using strong alkali such as alkali metal hydroxides like
KOH or NaOH, or with a mineral acid such as HCl, H.sub.2SO.sub.4,
etc., as required. Preferably the materials used to adjust pH
levels are aqueous solutions.
[0030] Consideration must be given to the fact that although this
invention has been described and disclosed in relation to certain
preferred embodiments, obvious equivalent modifications and
alterations thereof will become apparent to one of ordinary skill
in this art upon reading and understanding this specification and
the claims appended hereto. Accordingly, the presently disclosed
invention is intended to cover all such modifications and
alterations, and is limited only by the scope of the claims which
follow.
* * * * *