Patent Grant
9587350
The field of the invention relates to methods for deinking and decolorizing printed paper. More particularly, it relates to methods for removing ink from a paper pulp containing old newsprint.
The paper industry has been practicing wastepaper recycling to regenerate usable cellulosic fiber for paper making for many decades. In these processes, ink is removed from the wastepaper pulp using a suitable deinking composition. The deinking process produces a new paper or paperboard product out of materials that might otherwise have ended up in a landfill.
Because of increasing public demand, the use of recycled paper has steadily increased. To recover the fibers used for papermaking from wastepaper, a waste paper deinking operation must generally be carried out to remove the inks used in printing, and thus create suitable characteristics for re-use. Increasing amounts of wastepaper, e.g. old newspapers (ONP) and waste magazines (WM), are becoming available with increased participation of end consumers in recycling.
In the course of conventional paper reclamation, deinking procedures include steps for converting the wastepaper to pulp and contacting the pulp with an alkaline aqueous deinking medium containing a chemical deinking agent. The mechanical action and the alkalinity of the aqueous medium cause the partial removal of ink from the pulp fiber. The deinking agent completes this removal and produces an aqueous suspension and/or dispersion of the ink particles. The resulting mixture is subsequently treated to separate the suspended/dispersed ink from the pulp. This separation may be by flotation and/or washing techniques known in the art.
Conventional deinking chemicals comprise a complex mixture of chemicals, e.g. sodium hydroxide, sodium silicate, chelating agents, hydrogen peroxide, surfactants, dispersants, collector chemicals and agglomeration chemicals. In general, it is standard in deinking to include a significant amount of alkaline material, since it is believed that the alkaline material is needed for sufficient saponification and hydrolysis of the ink resins. In addition, mention is made of the fiber swelling by the caustic being partially responsible for the detachment of ink particles from the fiber surface. Typically, the pH during such a deinking process is from about 9.5 to about 11. Exposing the cellulosic and lignocellulosic fibers to this degree of alkalinity tends to cause yellowing of the fibers and, therefore, it is generally necessary to add an oxidative or reductive bleaching agent, such as peroxide or sodium hydrosulfite. The reductive bleaching step is commonly employed at the end of the deinking process while hydrogen peroxide is added at the pulper. In some deinking operations hydrogen peroxide will be added later in the process.
Furthermore, the alkaline method causes irreversible changes to the pulp fibers, and hence represents a cost to the facility in addition to just the cost of using the chemical. Using caustic will also solubilize papermaking additives and coatings that will lead to additional runnability problems due to deposits at the paper machine.
Thus, there is a need for a deinking process that avoids these shortcomings, which is safe and which is economically and environmentally desirable.
It has been found by the present inventors that treatment of a wastepaper containing pulp with an ink removing system in accordance with the present invention fulfills the above-mentioned requirements to such a deinking process.
The present invention is directed to a method for removing ink from printed paper. In one embodiment, the invention relates to removing ink from a pulp containing old news print (ONP) and maintaining or increasing brightness of the deinked pulp in a neutral deinking process.
In a first aspect, the invention is directed to a method for removing ink from printed paper, which comprises: (a) pulping printed paper at least 25 wt % of which is old newsprint at a consistency of at least about 3% to obtain a pulp slurry; (b) treating the pulp slurry with an ink removing system, which system comprises: (i) a combination of lipase and at least one second enzyme chosen from amylase, xylanase or cellulase, and (ii) a non-ionic surfactant, in amounts effective to release ink from said pulp slurry, wherein the lipase is present in an amount of at least about 0.001 wt % based on the dry content of the pulp slurry and the ratio of the at least one second enzyme:lipase is at least about 1.2:1; and (c) separating the released ink from the pulp slurry in a deinking step (e.g., a deinking flotation stage) to provide a deinked pulp slurry, wherein the treating step is carried out prior to the deinking step.
In one embodiment of the invention, the enzyme combination is a combination of lipase and xylanase. The ratio of xylanase:lipase can be at least about 1.5:1. In embodiments of the invention, the ratio of xylanase:lipase can be chosen from a ratio in the range of about 1.5:1 to about 5:1; about 1.5:1 to about 4:1; about 1.5:1 to about 3:1; about 1.5:1 to about 2.5:1; about 2:1 to about 4:1; or about 2:1 to about 3:1. In additional embodiments the ratio of xylanase:lipase can be chosen from about 2:1, 2.5:1 or 3:1.
In an embodiment of the invention, the non-ionic surfactant can be chosen from fatty acid alkoxylates, fatty alcohol alkoxylates or mixtures thereof. The non-ionic surfactant can be chosen from fatty alcohol ethyoxylates (FAEO), propoxylates (FAPO) and combinations thereof (FAEPO).
In embodiments of the invention, the ratio of (i):(ii) present in the ink removing system can be chosen from a ratio in the range of about 1:1 to about 1:10; about 1:1 to about 1:5; or about 1:2 to about 1:4.
In another aspect of the invention, the above ink removing system can further comprise (iii) a soap. In another aspect, the ink removing system can further comprise (iv) an alkaline reagent. In yet another aspect, the ink removing system can further comprise (iii) a soap and (iv) an alkaline reagent.
In one embodiment, the consistency can be in the range of about 3 to about 30%. In additional embodiments, the consistency can be chosen from a value in the range of about 10% to about 17%, or about 18 to about 23%.
In an embodiment of the invention, the printed paper comprises at least about 40 wt % ONP. In another embodiment, the printed paper comprises at least about 50 wt % ONP. In other embodiments, the printed paper comprises ONP in an amount chosen from within the range of from about 40 to about 95 wt %, about 45 to about 90 wt %, or about 50 to about 80 wt %. In yet another embodiment of the invention, the printed paper further comprises old magazine print (OMG).
In one embodiment, where the ink removing system comprises (iii) a soap and (iv) an alkaline reagent, the combination of enzymes (i) can be a combination of lipase and xylanase. In such an embodiment, the ratio of xylanase:lipase can be as discussed above.
In one embodiment of the invention, the soap can be fatty acid soap. In another embodiment, the fatty acid soap can be derived from tallow. In yet another embodiment, the fatty acid soap can be derived from plant oils.
In one embodiment of the invention, the alkaline reagent is sodium silicate. In one embodiment, the combination of enzymes (i) is a combination of lipase and xylanase; the non-ionic surfactant (ii) is chosen from fatty alcohol ethoxylates (FAEO), propoxylates (FAPO) and combinations thereof (FAEPO); the soap (iii) is a tallow fatty acid soap; and the alkaline reagent (iv) is sodium silicate. In such an embodiment, the ratio of xylanase:lipase and the ratio of (i):(ii) can be as discussed above.
In one aspect of the invention, components (i) and (ii) are premixed to form an enzyme composition (v) and then adding (v) to the pulp slurry as a component of the ink removing system. In one embodiment, the enzyme composition (v) is added to the pulp slurry in an amount in the range of about 0.04 to about 0.5 wt %, the soap (iii) is added to the pulp slurry in an amount in the range of about 0.1 to about 1 wt %, and the alkaline reagent (iv) is added to the pulp slurry in an amount in the range of about 0.5 to about 2 wt %, all based on the solid content of the slurry.
In one embodiment of the invention, the pH of the slurry is maintained in the range of about 6 to about 11. The preferred range is 6.7 to 9.5, the more preferred range is 7 to 9 and the most preferred range is 7.5 to 8.8.
In one embodiment of the invention, the slurry is substantially free of sodium sulfite. In another embodiment the slurry is substantially free of sodium hydroxide or, if added to the slurry, the sodium hydroxide is added in an amount less than about 0.15 wt %, based on the weight of the slurry. In yet another embodiment, the slurry is substantially free of hydrogen peroxide. In yet another embodiment, two or all of these requirements (of being free of a specified material) are met.
Additional objects, advantages and novel features will be apparent to those skilled in the art upon examination of the description that follows.
The present invention is directed to a method for removing ink from printed paper. In one embodiment, the invention relates to removing ink from a pulp containing old news print (ONP) and maintaining or increasing brightness of the deinked pulp in a neutral deinking process.
In one aspect the invention is directed to an ink removing system, which system comprises: (i) a combination of lipase and at least one second enzyme chosen from amylase, xylanase or cellulase, and (ii) a non-ionic surfactant, in amounts effective to release ink from said pulp slurry, wherein the lipase is present in an amount of at least about 0.001 wt % based on the dry content of the pulp slurry and the ratio of the at least one second enzyme:lipase is at least about 1.2:1.
In one embodiment of the invention, the enzyme combination is a combination of lipase and xylanase. The ratio of xylanase:lipase can be at least about 1.5:1. In embodiments of the invention, the ratio of xylanase:lipase can be chosen from a ratio in the range of about 1.5:1 to about 5:1; about 1.5:1 to about 4:1; about 1.5:1 to about 3:1; about 1.5:1 to about 2.5:1; about 2:1 to about 4:1; or about 2:1 to about 3:1. In additional embodiments the ratio of xylanase:lipase can be chosen from about 2:1, 2.5:1 or 3:1.
In embodiments of the method for removing ink, the total amount of enzyme added to the pulp slurry in the ink removal system is less than 0.5 lbs (0.23 kg), or 0.45 lbs (0.2 kg), or 0.4 lbs (0.18 kg), or 0.3 lbs (0.14 kg) per ton (2000 lbs) of dry pulp.
In embodiments of the method for removing ink, the components of the ink removing system are present in an amount to achieve an ink removal efficiency of at least about 50%, or at least about 60%, or at least about 70%, or at least about 80% in the subsequent deinking flotation stage. Ink removal efficiency means the percentage of ink removed based on the original amount of ink contained in the printed paper pulp prior to treating with the ink removal system and subjecting it to a deinking step to provide a deinked pulp. For example, 50% ink removal efficiency means the deinked pulp has 50% less ink than the starting printed paper pulp. In embodiments of the invention, the pulp slurry after the deinking step (e.g., deinking flotation stage) has a substantially reduced amount of ink, including the printing ink resins or oils of the type typically contained in printing ink systems.
In embodiments of the invention, the deinked pulp contains less than 0.2 wt % or is substantially free of vegetable oils and mineral oils found in printing inks. In an embodiment of the method for removing ink, no vegetable or mineral oil is added to the pulp slurry.
Examples of nonionic surfactants include a higher aliphatic alcohol alkoxylate, aliphatic acid alkoxylate, higher aromatic alcohol alkoxylate, fatty acid amide of alkanolamine, fatty acid amide alkoxylate, propylene glycol alkoxylate, block or random copolymer of ethylene and propylene oxide, or higher alcohol polyethylene polypropylene block or random adducts.
In an embodiment of the invention, the non-ionic surfactant can be chosen from fatty acid alkoxylates, fatty alcohol alkoxylates or mixtures thereof. The non-ionic surfactant can be chosen from fatty alcohol ethyoxylates (FAEO), propoxylates (FAPO) and combinations thereof (FAEPO). In an embodiment of the invention, the non-ionic surfactant is chosen or incorporated in a system to provide a low foaming deinking system. The non-ionic surfactant itself, or composition containing the surfactant, can be low foaming. Examples of commercially available surfactant products that are useful in the present invention include Eka RF 4000 and 4200 series deinking products available from Eka Chemicals, and in particular Eka RF 4031 and Eka RF 4291. In one embodiment, the Eka RF 4291 deinking product is preferred to be included.
In one aspect of the invention, the ink removing system can further comprise (iii) a soap. In another aspect, the ink removing system can further comprise (iv) an alkaline reagent. In yet another aspect, the ink removing system can further comprise (iii) a soap and (iv) an alkaline reagent.
The soap can be fatty acid soap. The fatty acid soap can be derived from tallow or can be derived from plant oils.
In one embodiment of the invention, the alkaline reagent is sodium silicate.
The following examples were conducted to evaluate the performance of deinking systems in a neutral deinking process:
Typical equipment, furnish and conditions used for examples 1-15 were as follows:
Equipment and Furnish
Conditions:
Pulper Chemistry and Deinking Dosage:
In each of the Examples, the tests were run in random order to prevent run order errors, but are listed in the tables out of sequence to group the tests according to the conditions used, e.g., cell level and enzymes used, to make analysis easier. In some Examples, test numbers have been omitted from the tables where duplicate tests were run or where a unique chemistry was used, e.g., another component was added, that makes the tests not relevant or not comparable to the present invention. In the case of duplicate tests, the results listed in the tables are an average of the results for the duplicate tests.
Regarding pulp liquor pH, while it is not always possible or easy to measure the pH of the combined pulping chemicals and dilution water in a particular mill setting in real time, it can be measured in a lab setting. Accordingly, in the following examples the measured pH of the combined chemicals and the dilution water is referred to as the “Pulp Liquor pH”, which is helpful in seeing how changes in alkaline reagents addition impact of pH.
The pulping recipes used in Example 1 (Tests 1-16) are listed below in Table 4. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges used for Example 1 are listed below in Table 5.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 6.
In addition to the results in Table 6, the following was observed: tests 3, 5 and 6 had less foam with less rejects generated; tests 7 and 8 (with enzyme blends) gave the best ink removal; tests 11, 12, 15 and 16 had too much wet rejects; and test 13 showed good ink removal but too much rejects. For this Example a reject amount over about 350 g was considered too high a yield loss.
The results of the deinking tests for Example 1 are shown graphically in
The pulping recipes used in Example 2 (Tests 1-16) are listed below in Table 7. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Example 2 are listed below in Table 7.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 9.
In addition to the results in Table 9, the following was observed: tests 5-8 and 11-16 had too much rejects. For this Example a reject amount over about 400 g was considered too high a yield loss.
The results of the deinking tests for Example 2 are shown graphically in
The pulping recipes used in Example 3 (Tests 1-17) are listed below in Table 10. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Example 3 are listed below in Table 11.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 12.
In addition to the results in Table 12, the following was observed: tests 6 and 10-16 had too much rejects. For this Example a reject amount over about 570-600 g was considered too high a yield loss.
The results of the deinking tests for Example 3 are shown graphically in
The pulping recipes used in Examples 4 and 5 (Tests 1-30) are listed below in Table 13. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT (Example 4) and 35 grams of Globe and Mail mixed (Example 5), flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Examples 4 and 5 are listed below in Table 14.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 15.
In addition to the results in Table 15, the following was observed: tests 5, 9, 11-15, 17, 20-22, 25, 29 and 30 had too much wet rejects. For this Example a reject amount over about 850 g was considered too high a yield loss.
The results of the deinking tests for Examples 4 and 5 are shown graphically in
The pulping recipes used in Examples 6 and 7 (Tests 1 to 17) are listed below in Table 16. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT (Example 6) and 35 grams of Globe and Mail mixed (Example 7), flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Examples 6 and 7 are listed below in Table 17.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 18.
For this Example a reject amount over about 700 g was considered too high a yield loss. In addition to the results in Table 18, the following was observed: tests 14 had too much wet rejects.
The results of the deinking tests for Examples 6 and 7 are shown graphically in
The pulping recipes used in Example 8 (Tests 1 to 7) are listed below in Table 19. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Example 8 is listed below in Table 20.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 21.
For this Example a reject amount over about 1130 g was considered too high a yield loss. In addition to the results in Table 21, the following was observed: tests 4 to 6 had too much wet rejects.
The results of the deinking tests for Example 8 are shown graphically in
The pulping recipes used in Example 9 (Tests 1 to 14) are listed below in Table 22. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 8 min, and air rate of 20 SCHF. The pH operating ranges for Example 8 is listed below in Table 23.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 24.
For this Example a reject amount over about 920 g was considered too high a yield loss. In addition to the results in Table 24, the following was observed: no tests had too much wet rejects.
The results of the deinking tests for Example 9 are shown graphically in
The pulping recipes used in Example 10 (Tests 1 to 14) are listed below in Table 25. The specific pulping components and conditions were: 35 grams each of WSJ, LAT or Globe and Mail, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 10 is listed below in Table 26.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 27.
For this Example a reject amount over about 380 g (LA Times), 590 (WSJ) or 690 (Globe and Mail) was considered too high a yield loss. In addition to the results in Table 27, the following was observed: no tests had too much wet rejects.
The results of the deinking tests for Example 10 are shown graphically in
The pulping recipes used in Example 11 (Tests 1 to 23) are listed below in Table 28. A portion of the tests were not related to this study and are not included. The specific pulping components and conditions were: 35 grams each of WSJ, LAT or Globe and Mail, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 11 is listed below in Table 29.
The deinking performance of the various test recipes were evaluated and the results are shown below in Table 30.
For this Example a reject amount over about 380 g (LA Times), 590 (WSJ) or 690 (Globe and Mail) was considered too high a yield loss. In addition to the results in Table 30, the following was observed: test 23 was barely above having too much wet rejects.
The results of the deinking tests for Example 11 are shown graphically in
The pulping recipes used in Example 12 are listed below in Table 32. A portion of the tests were not related to this study and are not included or were repeats averaged into the reported results. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 12 is listed below in Table 33.
For this Example a reject amount over about 1030 g (Eka RF 4291) or 920 (Eka NA120) was considered too high a yield loss. In addition to the results in Table 34, the following was observed: none of the tests had too much wet rejects.
The results of the deinking tests for Example 12 are shown graphically in
The pulping recipes used in Example 13 (Tests 1-14) are listed below in Table 35. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 13 is listed below in Table 36.
For this Example a reject amount over about 1020 to 1070 g was considered too high a yield loss. In addition to the results in Table 37, the following was observed: none of the tests had too much wet rejects.
The results of the deinking tests for Example 13 are shown graphically in
The pulping recipes used in Example 14 (Tests 1-14) are listed below in Table 38. The specific pulping components and conditions were: 17.5 grams each of WSJ and LAT, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 14 is listed below in Table 39. This study used a pulping consistency of 20%.
For this Example a reject amount over about 790 g was considered too high a yield loss. In addition to the results in Table 40, the following was observed: none of the tests had too much wet rejects.
The results of the deinking tests for Example 14 are shown graphically in
The pulping recipes used in Example 15 (Tests 1-14) are listed below in Table 41. The specific pulping components and conditions were: 50.0 grams mixture of old newspaper using flexographic ink and coated paper, flotation time of 5 min, and air rate of 15 SCHF. The pH operating ranges for Example 15 is listed below in Table 42. This study used a pulping consistency of 20%.
The ink fragmentation test conditions were within the range of conventional deinking except for the neutral deinking tests that included hydrogen peroxide. For ERIC values after flotation all of the neutral deinking conditions matched or out preformed conventional deinking. Except for cellulase all of the other neutral deinking conditions gave equal to better ink detachment.
All of the neutral deinking conditions were within 2 points of conventional deinking after flotation. Tests that included Xylanase, Xylanase/Lipase and peroxide had higher brightness than the sulfite based neutral deinking.
The hyperwash brightness after flotation was within two points of conventional deinking expect for tests that included sodium sulfite and lipase alone, cellulase alone, or amylase alone.
The tests that included lipase and hydrogen peroxide tended to have the highest levels of rejected material. However, the hydrogen peroxide tests were not been conducted at lower air injection rates.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10164835 | Mar 2010 | EP | regional |
This application is a national stage filing under 35 U.S.C. §371 of PCT/US2011/024501, filed Aug. 18, 2011, which claims priority to U.S. Provisional Patent Application No. 61/303,828, filed on Feb. 12, 2010, and European Patent Application No. 10164835.0, filed Mar. 6, 2010, the contents of which are incorporated herein by reference in their entirety.
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| WO2011/100530 | 8/18/2011 | WO | A |
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| 20120305206 A1 | Dec 2012 | US |
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