WO2012093395A2

WO2012093395A2 - A method and composition for deinking a printed substrate

Info

Publication number: WO2012093395A2
Application number: PCT/IL2012/000008
Authority: WO
Inventors: Matti Ben-Moshe; Zach Barnea
Original assignee: Freeink Ltd.
Priority date: 2011-01-06
Filing date: 2012-01-05
Publication date: 2012-07-12
Also published as: WO2012093395A3; IL210497A0

Abstract

The invention provides a method for deinking a printed substrate comprising subjecting the printed substrate to treatment with plasma and with a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound.

Description

A METHOD AND COMPOSITION FOR DEINKING A PRINTED SUBSTRATE

The present invention relates to a method and composition for deinking a printed substrate said composition comprising at least one organic solvent and a quaternary ammonium compound and said method comprising treatment of a printed substrate with plasma, soaking in said solvent mixture, applying a mechanical force to completely remove the printed matter from the substrate without harming the printed substrate and preparing the substrate to be printed again.

BACKGROUND

Recycling of printed office and industrial papers (photocopy, inkjet and laser prints) is a major challenge due to the difficulty in removing a print of small particle size pigments.

Paper is a thin material used for writing, printing, cleaning, packaging and other construction applications. Papers are produced by pressing together cellulose fibers and drying them into a flexible sheet.

Paper recycling is the process of recovering waste paper and reprocessing it into a new paper product. Paper is one of the main targets for recycling. 45% of all paper used in the United States is recycled. A major concern about recycling wood pulp paper is that the fibers are degraded with each cycle and become too mechanically weak to be useful in making paper.

Deinking is the industrial process of removing printing ink from paper fibers of recycled paper to make deinked pulp. Pulp is a dry fibrous material prepared by chemically or mechanically separating fibers from wood or waste paper. The primary goal of the deinking process is to detach ink from the paper fibers. In common industrial methods this is achieved by a combination of mechanical and chemical means.

Printing on paper can be carried out using two distinct printing ink categories: impact or non-impact printing. In impact printing, generally used for newsprint, the ink does not bind to the paper and therefore is easy to remove or disperse during deinking. Unlike impact printing inks, non-impact inks used in photocopying, ink-jet and laser printing results in ink impregnating into the paper and making it difficult to disperse, thus rendering the common deinking processes non-applicable.

Laser printing, HP Electro-Ink and inkjet printing technologies are the most common printing technologies for home, office and several variable data and small series industrial applications.

Laser printing technology is based on a laser beam projecting a digital image copy of the printed page onto a charged rotating drum. Then the drum rolls and picks up dry ink particles, only from those regions that are still charged. Then the drum imprints ink onto paper, by heat and direct contact with the printed -paper. The dry ink particles are referred to as a Toner. Toner is made of a fine powder that contains a pigment and different polymers such as binders and/or surface modifiers and additives. High quality toner powder is super fine, while the ones of lesser quality are made of more course powders. The pigment particle size in a toner is usually 5 microns or greater. To improve image resolution, particle size is further reduced. The function of the binder is to hold the pigment in place in the final image. It also provides gloss to the image area. The polymer used varies by manufacturer but can be a styrene acrylate copolymer, a polyester resin, a styrene butadiene copolymer, or a few other special polymers.

Two principal uses of laser printing technology in the office are for printing paper and photocopying. Both of the processes use a toner material to create the image. The various types of toners are thermosetting plastic resins with carbon black and other minor constituents to control flow properties, electrical and magnetic properties or other additives.

Another laser-assisted printing technology is the HP-Indigo Electroink (Ness Ziona, Israel). According to HP company data the HP Electroink technology is based on a unique liquid ink that combines the advantages of electronic printing with the qualities of liquid ink. HP Electroink contains charged pigmented particles in a liquid carrier, and enables digital printing by electrically controlling the location of these particles. Like other digital printing technologies, i.e. powder toner xerography (laser printing technology), Electroink enables digital printing by electrically controlling the location of the print particles. However, unlike powder toner xerography, Electroink enables very small particle size, down to 1-2 microns. This small particle size enables higher resolution, higher gloss, sharp image edges, and very thin image layers. In powder toner xerography, on the other hand, the particle size cannot be made too small, as particles then become airborne, and uncontrollable. Therefore, the higher the printing speed in digital printers, the larger the particle sizes must become. Electroink, being electrically charged particles in liquid, enables controlling even the smallest particle sizes required for quality color printing.

Ink Jet printing is a non impact printing process in which droplets of ink are deposited on a substrate, such as paper, to form the digital image. Ink Jet printers are loaded with an ink for full color printing typically comprises a cyan, magenta, yellow and Black inks (CMYK).

There are two primary types of inkjet printing technologies; continuous and drop-on- demand. Both types of inkjet printing involve liquid ink that is broken up into individual droplets by high frequency vibration when it is ejected from the nozzles. Drop-on-demand inkjet printing devices generate ink droplets when needed using a thermal (bubble) or piezoelectric mechanism. Continuous inkjet printers utilize electrostatic charging to continuously supply an ink stream at high velocity to the nozzles during printing. These electrostatic charging devices break the ink fluid into individual ink droplets, which are directed towards the paper substrate or towards an ink-capturing device. Both drop-on- demand and continuous inkjet printing technologies have broad applications as printing devices for home, office and industrial printing applications.

The inkjet printing ink has three basic components: a solvent, a colorant, and a humectant. The humectant is a nonvolatile co solvent (such as diethylene glycol or ethylene glycol), which absorbs water from the air and keeps the nozzle moist and clog free. The colorant is either a dye or a pigment. Dyes are soluble in the solvent, have a uniform homogenous phase, and easily pass through the nozzle. Pigments are non-soluble particles that must be dispersed in the solvent, and can dry out and form aggregates which clog inkjet nozzles.

Quaternary ammonium cation, also known as an Aliquat, is a positively charged ion of the structure NR4+, R being an alkyl group or an aryl group. Unlike the ammonium ion (NH4+) and the primary, secondary, or tertiary ammonium cation, the quaternary ammonium cation is permanently charged, independent of the pH of their solution. Quaternary

ammonium salts or quaternary ammonium compounds are salts of quaternary ammonium cation with a counter anion. Specific examples of the quaternary ammonium salts include lauryl-tri-methyl-ammonium bromide, lauryl-tri-methyl-ammonium chloride, cetyl-tri- methyl-ammonium bromide, cetyl-tri-methyl-ammonium chloride, octa-iso-quinolinium bromide, octa-iso-quinolinium chloride, hexa-decyl-tri-methylammonium bromide, and hexa- decyl-tri-methylammonium chloride.

More examples of Quaternary ammonium compounds are those selected from the group of Acetylcarnitine, Acetylcholine, Aclidinium bromide, Acriflavine, Aliquat 336, Ambenonium chloride, Ambutonium bromide, Aminosteroid, Atracurium besilate,

Benzalkonium chloride, Benzethonium chloride, Benzilone, Benzododecinium bromide, Benzoxonium chloride, Benzyltrimethylammonium fluoride, Bephenium, Berberine, Betaine, Bethanechol, Bevonium, Bibenzonium bromide, Bretylium, Butylscopolamine,

Butyrylcholine, Candocuronium iodide, Carbachol, Carbethopendecinium bromide, Carnitine, Cefluprenam, Cetrimonium, Cetrimonium chloride, Cetrimonium bromide, Cetylpyridinium chloride, Chelerythrine, Chlorisondamine, Choline, Choline chloride, Cimetropium bromide, Cisatracurium besilate, Citicoline, Clidinium bromide, Clofilium, Cocamidopropyl betaine, Cocamidopropyl hydroxysultaine, Cyanine, Decamethonium, 3-Dehydrocarnitine,

Demecarium bromide, Denatonium, Dequalinium, Didecyldimethylammonium chloride, Dimethyldioctadecylammonium chloride, Dimethylphenylpiperazinium,

Dimethyltubocurarinium chloride, Diphemanil metilsulfate, Diphthamide, Diquat,

Distigmine, Domiphen bromide, Doxacurium chloride, Echothiophate, Edrophonium,,, Emepronium bromide, Ethidium bromide, Euflavine, Fenpiverinium, Fentonium, Gallamine triethiodide, Gantacurium chloride, Glycine betaine aldehyde, Glycopyrrolate, Guar, hydroxypropyltrimonium chloride, Hemicholinium-3, Hexafluronium bromide,

Hexamethonium, Hexocyclium, Homatropine, Hydroxyethylpromethazine, Ipratropium,, Isometamidium chloride, Isopropamide, Jatrorrhizine, Laudexium metilsulfate, Lucigenin, Mepenzolate, Meratran, Methacholine, Methantheline, Methiodide, Methscopolamine, Methylatropine, Methylscopolamine, Metocurine, Miltefosine, Muscarine, Neurine,

Obidoxime, Otilonium bromide, Oxapium iodide, Oxyphenonium bromide, Palmatine, Pancuronium bromide, Pentamine, Penthienate, Pentolinium, Phellodendrine,

Phosphocholine, Pinaverium, Pipecuronium bromide, Pipenzolate, Poldine, Pralidoxime, Prifinium bromide, Procyclidine, Propantheline bromide, Prospidium chloride,

Pyridostigmine, Pyrvinium, Quaternium-15, Quinapyramine, Rapacuronium, Rocuronium bromide, Sanguinarine, Stearalkonium chloride, Succinylmonocholine, Suxamethonium chloride, Tetra-n-butylammonium bromide, Tetra-n-butylammonium fluoride,

Tetrabutylammonium hydroxide, Tetrabutylammonium tribromide, Tetraethylammonium, Tetraethylammonium bromide, Tetramethylammonium chloride, Tetramethylammonium hydroxide, Tetramethylammonium pentafluoroxenate, Tetraoctylammonium bromide, Tetrapropylammonium perruthenate, Thiazinamium metilsulfate, Thioflavin, Tibezonium iodide, Tiemonium iodide, Timepidium bromide, Tridihexethyl, Triethylcholine, Trigonelline, Trimethyl ammonium compounds, Trimethylglycine, Trolamine salicylate, Trospium, Tubocurarine chloride, Vecuronium bromide.

Plasma treatment refers to the use of an ionized gas at either low pressure or atmospheric pressure to either increase (make hydrophilic) or decrease (make hydrophobic) surface energy. Plasma treatment is commonly used as a surface preparation method prior to printing, bonding and coating substrate surfaces. The plasma treatment processes described herein are not intended to include laser as part of the plasma source.

Corona treatment (air plasma) is a surface treatment process that improves the bonding characteristics of most materials such as: paper, films, foils, and polymers by raising its surface energy. Corona treatment is the standard surface treatment method used in the plastic film, extrusion, and converting industries.

Several deinking technologies have been previously proposed for deinking printed office paper.

JP1101576 discloses a method to reproduce copied paper by immersing paper coated with toner in a toner resin-soluble solvent, applying ultrasonic wave oscillation to the solution and liberating the toner dissolved in the solvent from the paper surface. However, this invention is related to methods and devices to recycle digital copy sheets through thermal fixing and does not involve application of plasma treatment nor is it applicable for deinking inkjet printing.

JP4091298 discloses a method to recycle copying paper without any change in quality of paper itself by adding a surfactant to a printing removing solvent, etc., dipping copied paper in the resultant mixture solution, washing the copied paper, removing the printing from the paper and then drying the prepared paper. This patent discloses a process of recycling used copy paper, wherein the cleaning process is divided into two steps: step 1 immerses printed paper into a water-containing solution (pre-treatment liquor); step 2 cleans the pre- treated copy paper with a water-free deinking solution or a surfactant-added deinking solution.

JP4300395 discloses a method for regeneration of a waste copying paper produced from a copying apparatus by removing toner as a printing component from the waste copying paper. Specifically, a solvent such as chloroform is made to adhere to printed parts by immersion, spraying or coating so as to dissolve the toner. The dissolved toner component is then removed by washing, suction, adsorption, etc., thus regenerating copying papers.

W09947743 discloses a method of deinking a sheet of paper by wetting the sheet of paper with a non-toxic, water soluble deinking solution including; water, thereby wetting the sheet of paper to swell the fibers of said sheet, and using a water soluble surfactant for lowering the surface tension of said water to enhance wetting of the sheet with said water, and no more than two water soluble solvents for softening the toner, without dissolving the toner, and for breaking the bond between the toner and the sheet; removing the softened toner from the sheet, creating toner particles; heating the sheet to vaporize the deinking solution, removing the solution from the sheet; and calendering the sheet of paper to return the sheet to its original size for immediate reuse. However, this method uses a water-based composition and has limited industrial applicability, as swelling of the paper fibers occurs and the paper is no longer usable. Also, this patent discloses a method for deinking laser printed-paper only by softening and breaking the bond between the toner and the sheet but without dissolving or dispersing the toner.

WO2007017889 discloses a process for enzymatic deinking of office waste paper inclusive of xerographic and inkjet-printed paper printed with non impact and non dispersible ink using the cell free culture supernatant of Vibrio alginolyticus or immobilized cells of the same bacterium having the accession number NIO/DI/32 and deposited at ARS Patent Culture Collection, USA, under the Number NRRL-B-30638. Further, said invention relates to decolorization of office waste paper pulp within 72 h after contacting the said enzymes from the said bacterium in the pulp of 3-12% consistency in seawater. Decolorization is achieved by using extracellular enzymes produced by the bacterium NIO/DI/32 grown in nutrient broth supplemented with starch or Tween-80. However, this patent provides an enzymatic route for deinking of pulp and not for deinking office paper. Also enzymatic methods are not efficient in removing pigment such as carbon black containing inks.

WO9722750, W09512550 and WO0015899 disclose a process for deinking of office wastepaper stocks that are limited to wastepaper converted to a pulp.

WO9705323 discloses a device for removing ink from laser print paper comprising an adhesion roller or belt for heating and applying pressure on the sheet of paper, softening the thermosetting ink film surface, reducing the adhesion of the ink to the sheet of paper, and improving the adhesion of the ink to the adhesion roll. After adhesion of ink to the roll, the paper sheet is peeled away leaving the ink toner fused to the adhesion roll. The roll is then cleaned of fused ink and is ready for the next paper sheet. Again, this patent removes a softened toner film without dissolving or dispersing it into a cleaning solution.

US5353108 discloses a cleaning apparatus for cleaning an erasable paper having a surface which has been treated with a releasing agent and on which a pattern of a heat-soluble ink has been printed, comprising: an adhesion roller having an outer surface made of a heat- soluble resin which has been placed in a tacky state by heating; and a platen for pressing said erasable paper onto the outer surface of said adhesion roller; said adhesion roller rotating to transport said erasable paper inserted between the outer surface of said adhesion roller and said platen while peeling off the pattern of the heat-soluble ink from the surface of said erasable paper.

However, this patent has limited industrial applicability due to the fact that the printed- paper to be deinked should have its surface pre-treated with a releasing agent.

DE 19646421 discloses a method of removing toner images by swelling the toner image by immersing the copying medium with the image in an organic deinking fluid in a process vessel; and (b) mechanical removal of the image by contact pressure exerted on the front and back of the medium by a pair of contact elements. The fluid comprises butyro- lactone, glycol ether(s) or ester(s), and/or hydroxy-ether(s) or -ester(s) of formula (III), where Rl, R2 and R4 are each methyl (Me), ethyl (Et), propyl, butyl or acetyl; R3 and R5 are each hydrogen (H), Me or Et; and n = 1-4.

However, non of the above prior art publications teach or suggest a method for complete removal of inkjet or laser printed matter by utilizing plasma treatment in

combination with a solvent mixturecomposition comprising an organic solvent and a quaternary ammonium compound while allowing recycling the substrate to be printed again.

Thus, with this state of the art in mind , there is now provided, according to the present invention, a method for deinking a printed substrate comprising subjecting said printed substrate to treatment with plasma and with a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound.

In preferred embodiments of the present invention there is provide a method for deinking a printed substrate comprising subjecting said printed substrate to:

(i) treatment with plasma;

(ii) soaking in a solvent mixture comprising at least one organic solvent and a

quaternary ammonium compound;

(iii) applying a mechanical force to completely remove the printed matter from the substrate; and

(iv) preparing the substrate to be printed again.

According to one embodiment of the present invention the substrate is an inkjet printed substrate, such as paper, polymer, metal coated polymers, plastic, wood, metal, glass, ceramics or fabric just to name a few.

According to another embodiment of the present invention, the substrate is printed with a laser printer or other laser assisted printing technology such as HP Electrolnk technology (Hewlett Packard, Ness Ziona, Israel).

According to another embodiment of the present invention the printed colorant is a pigment, with a particle size (D50) smaller than 10 μηι; preferably smaller than 5 μιη; even more preferably smaller than 1 μηι; most preferably smaller than 100 nm; and even smaller than 30 nm.

According to another embodiment of the present invention the solvent is an organic polar or non-polar (a-polar) solvent selected according to it's polarity from alkanes, alkenes, ethers, halogenated hydrocarbons, aromatic hydrocarbons, aldehydes and ketones, esters, alcohols, amines and carboxylic acids. Exemplary solvents include but are not limited to ethylene glycol, diethylene glycol, Ethylene glycol monobutyl ether (EGMBE), isopropyl alcohol (IP A), n-methyl pyrrolidone (NMP), methoxy propyl acetate (MP A), di-acetone alcohol (DAA), methoxy propanol, methyl alcohol, ethyl alcohol, methyl lactate, ethyl lactate, 2-butanone, 2-pyrrolidone, 1,4 butanediol, dimethyl sulphoxide (DMSO), glycol ethers, particularly propylene glycol n-butyl ether, dipropylene glycol, tripropylene glycol, 2-methyl- 1,3 -propanediol, propylene glycol methyl ether, propylene glycol ethyl ether, dipropylene glycol methyl ether, dipropylene glycol n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol n-butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol n-propyl ether, dipropylene glycol n-propyl ether, diethylene glycol n-butyl ether, triethylene glycol butyl ether, diethylene glycol methyl ether, triethylene glycol methyl ether.

According to another embodiment of the present invention the solvent contains up to 10% of water, and most preferably up to 50% water.

According to another embodiment of the present invention the substrate is soaked in the solvent mixture for more than 1-120 seconds, more preferably 2-60 seconds and most preferably 5-30 seconds.

According to another embodiment of the present invention the substrate is soaked in the solvent mixture at elevated temperatures of more than 120°C, more preferably more than 80°C and most preferably more than 50°C.

According to another embodiment of the present invention a mechanical force is applied at the end of the deinking process to completely remove the ink from the substrate. The mechanical force is preferably applied by sonication, vibration, pressurized solvent jet, solvent stream, by tapping, applying frication, applying pressure or by applying vacuum. The mechanical force according to the current embodiment is applied to either sides of the substrate to be deinked.

According to another embodiment of the present invention at least 80% of the pigment is removed from the printed substrate, more preferably more than 90% of the pigment is removed, even more preferably more than 95% of the pigment is removed and most preferably more than 98% of the pigment is removed. According to preferred embodiments practically all the printed pigment is removed from the substrate so identification of the printed pattern is not possible after completion of the deinking process.

While the invention will now be described in connection with certain preferred embodiments in the following description and with reference to the accompanying figure so that aspects thereof may be more fully understood and appreciated, it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention as defined by the appended claims. Thus, the following examples which include preferred embodiments will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrative discussion of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention.

In the Drawings:

Figures la, lb and lc schematically illustrate three different flow diagrams for deinking a printed substrate according to preferred embodiments of the present invention.

The figures represent several possible embodiments of the present invention illustrating the subsequent combination of plasma and solvent mixture comprising at least one organic solvent and a quaternary ammonium compound for complete removal of the ink from the printed paper.

According to one embodiment presented in figure la the printed paper is plasma treated followed by washing out the print with a pressurized jet comprising at least one organic solvent and a quaternary ammonium compound.

According to a second embodiment illustrated in figure lb the printed paper is plasma treated followed by immersion in a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound and sonication to completely remove the print.

According to a third embodiment illustrated in figure lc the printed-paper is first immersed in a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound followed by plasma treatment and sonication in the same solvent mixture to completely remove the print.

Example 1

A paper was printed with Kyocera FS-3900 laser printer using a TK-320 cartridge. The paper was plasma treated at a rate of 2 m/s followed by washing with a pressurized jet of Ethyl acetate containing 5% di-dodecylammonium bromide for 5 seconds. The paper was allowed to dry and its physical properties were preserved whereby reprinting thereon was possible.

Example 2

A paper was printed with HP6500 inkjet printer using HP920XL cartridge. The paper was plasma treated at a rate of 0.5 m/s followed by immersion and sonication in butyl acetate containing 5% tetra-butyl ammonium fluoride for 60 seconds. The paper was allowed to dry and its physical properties were preserved whereby reprinting thereon was possible.

Example 3

A paper was printed with HP Indigo 3500 Press. The paper was plasma treated at a rate of 1 m/s followed by immersion and sonication in butyl acetate containing 5% tetra-butyl ammonium fluoride for 5 seconds. The paper was allowed to dry and its physical properties were preserved whereby reprinting thereon was possible

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative examples and attached figures and that the present invention may be embodied in other specific forms without departing from the essential attributes thereof, and it is therefore desired that the present embodiments and figures be considered in all respects as illustrative and not restrictive, reference being made to the appended claims, rather than to the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

WHAT IS CLAIMED IS:

1. A method for deinking a printed substrate comprising subjecting said printed substrate to treatment with plasma and with a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound.

2. A method for deinking a printed substrate comprising subjecting said printed substrate to:

(i) treatment with plasma;

(ii) soaking in a solvent mixture comprising at least one organic solvent and a quaternary ammonium compound;

(iv) preparing the substrate to be printed again.

3. A deinking method according to claim 1, wherein the substrate was printed by inkjet printing technology.

4. A deinking method according to claim 1, wherein the substrate was printed by laser printing.

5. A deinking method according to claim 1, wherein the substrate was printed by the Electrolnk-printing technology.

6. A deinking method according to claim 1, wherein the printed substrate is made of paper, polymer, metal coated polymers, plastic, wood, metal, glass, ceramics or fabric.

7. A deinking method according to claim 1, wherein the printed matter contains pigment particles with a particle size (D50) smaller than 10 microns.

8. A deinking method according to claim 1, wherein the printed matter contains pigment particles with a particle size (D50) smaller than 5 microns.

9. A deinking method according to claim 1, wherein the printed matter contains pigment particles with a particle size (D50) smaller than 1 micron.

10. A deinking method according to claim 1 , wherein the printed matter contains pigment particles with a particle size (D50) smaller than 100 nm.

11. A deinking method according to claim 1, wherein the printed matter contains pigment particles with particle size (D50) smaller than 30 nm.

12. A deinking method according to claim 1, wherein the solvent is a polar organic solvent.

13. A deinking method according to claim 1, wherein the solvent is an a-polar organic solvent.

14. A deinking method according to claim 1, wherein the solvent contains up to 50% water.

15. A deinking method according to claim 1, wherein the solvent contains up to 10% water.

16. A deinking method according to claim 1, wherein the applied mechanical force is applied by sonication.

17. A deinking method according to claim 1, wherein the mechanical force is applied by vacuum or suction.

18. A deinking method according to claim 1, wherein the mechanical force is applied by pressurized solvent stream.

19. A deinking method according to claim 1, wherein the mechanical force is applied by vibration.

20. A deinking method according to claim 1, wherein the printed substrate is soaked for 1-120 seconds.

21. A deinking method according to claim 1, wherein the printed substrate is soaked for 2-60 seconds.

22. A deinking method according to claim 1, wherein the printed substrate is soaked for 5-30 seconds.

23. A deinking method according to claim 1, wherein the solvent temperature is more than 120°C.

24. A deinking method according to claim 1, wherein the solvent temperature is more than 80°C.

25. A deinking method according to claim 1, wherein the solvent temperature is less than 50°C.

26. A deinking method according to claim 1, wherein at least 80% of the printed pigment is removed.

27. A deinking method according to claim 1 , wherein at least 90% of the printed pigment is removed.

28. A deinking method according to claim 1, wherein at least 95% of the printed pigment is removed.

29. A deinking method according to claim 1, wherein at least 98% of the printed pigment is removed.

30. A deinking method according to claim 1, wherein the printed substrate is first corona treated prior to soaking in the solvent mixture

31. A deinking method according to claim 1, wherein the printed substrate is first plasma treated prior to soaking in the solvent mixture.

32. A deinking method according to claim 1, wherein the printed substrate is first soaked in the solvent mixture prior to plasma treatment.

33. A deinking composition for use in the method of claim 1 comprising at least one organic solvent and a quaternary ammonium compound.