PROCESS FOR THE DEINKING OF COATED PAPER OR PAPERBOARD

Abstract

A process for the deinking of a coated paper or paperboard is disclosed, the process comprises a step of providing a coating layer comprising a calcium- or magnesium-exchanged clay which is deposited on the paper or paperboard before the ink layer. In a further step said calcium- or magnesium-exchanged clay is activated and the paper is subsequently treated with water.

Claims

1. A process for the deinking of coated paper or paperboard, comprising the following steps: (i) providing a coated paper or paperboard comprising, (a) at least one layer consisting of a coating composition comprising, (a1) a calcium- or magnesium-exchanged clay, (a2) a binder, (b) at least one layer having a thickness in the range from 0.1 to 10 m comprising ink, (ii) activating the calcium- or magnesium-exchanged clay before or during step (iii) by, (A) carrying out step (iii) with water comprising monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof, and/or (B) providing in step (i) a binder (a2) that is soluble in water and comprises monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof, and/or (C) adding monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof in form of a salt before or during step (iii), (iii) treating the coated paper or paperboard as provided in step (i) with water to obtain an aqueous suspension comprising at least ink, clay particles and a paper pulp or a paper residue, wherein layer (a) is deposited on the paper or paperboard before layer (b).

2. The process according to claim 1, wherein the process comprises a further step (iv) of separating the paper or paperboard from the aqueous suspension obtained in step (iii).

3. The process according to claim 1 or 2, wherein the clay is a calcium-exchanged nanoclay selected from the group consisting of bentonite, smectite, montmorillonite and mixtures thereof and preferably is bentonite.

4. The process according to claim 1, wherein the activating step (ii) is, (A) carrying out step (iii) with water comprising an excess of monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof with respect to calcium or magnesium ions, wherein sodium ions are preferred and/or (B) providing in step (i) a binder (a2) that is soluble in water and comprises monovalent ions selected from the group consisting of sodium, lithium, potassium, ammonium and mixtures thereof with respect to calcium or magnesium ions, wherein sodium ions are preferred and/or (C) adding sodium ions in form of a salt selected from the group consisting of sodium chloride, sodium nitrate, sodium sulphate, sodium carbonate and mixtures thereof before or during step (iii).

5. The process according to claim 1, wherein the binder is water soluble and selected from the group consisting of starch, carboxymethylcellulose, and mixtures thereof and preferably is carboxymethylcellulose, more preferably the water-soluble binder comprises an excess of sodium ions with respect to calcium or magnesium ions and/or the coating composition comprises another binder which is water-dispersible, preferably a latex-binder.

6. The process according to claim 1, wherein the coated paper comprises at least one layer (c) comprising 1 to 30 g/m.sup.2, preferably from 5 to 20 g/m.sup.2 and more preferably 6 to 15 g/m.sup.2 of a calcium carbonate-comprising material.

7. The process according to claim 6, wherein the calcium carbonate-comprising material is selected from ground calcium carbonate, precipitated calcium carbonate, surface-modified calcium carbonate, or a mixture thereof, and preferably is a natural ground calcium carbonate.

8. The process according to claim 6 or 7, wherein the calcium carbonate-comprising material is selected from natural calcium carbonate sources and preferably is selected from the group consisting of marble, limestone, chalk, dolomite, and mixtures thereof.

9. The process according to claim 1, wherein the thickness of the at least one ink layer is in the range from 0.75 to 5 m and preferably in the range from 0.9 to 2.1 m.

10. The process according to claim 1, wherein the water applied in step (iii) is selected from the group consisting of tap water, deionized water and mixtures thereof, preferably is tap water, more preferably is tap water comprising sodium ions, even more preferably is tap water comprising an excess of sodium ions with respect to calcium or magnesium ions.

11. The process according to claim 1, wherein mechanical scraping of the surface of the paper or paperboard is carried out during step (iii).

12. The process according to claim 1, wherein the content of the calcium- or magnesium-exchanged clay (a1) in the coating composition, is in the range from 3 to 15 wt.-%, more preferably 5 to 12 wt.-% and most preferably from 5 to 10 wt.-% based on the total weight of the coating composition, and/or the coating weight of the at least one layer (a) is from 0.1 to 20 g/m.sup.2, preferably 1 to 10 g/m.sup.2.

13. The process according to claim 1, wherein the content of the binder (a2) in the coating composition is in the range from 0.1 to 12 wt.-%, more preferably from 0.2 to 5 wt.-%, even more preferably from 0.3 to 2.0 wt.-% and most preferably from 0.5 to 1.5 wt.-% based on the total weight of the coating composition.

14. The process according to claim 1, wherein the ink in layer (b) is a digital printing ink selected from the group consisting of ink- or dye-based inkjet inks, laser printing inks and/or toners, offset inks, flexographic inks, rotogravure inks and mixtures thereof.

15. The process according to claim 1, wherein the process further comprises the steps of (v) transferring the aqueous suspensions as obtained in step (iii) or (iv) to a flotation cell, and/or (vi) adding at least one collector agent to the aqueous suspensions as obtained in step (iii), (iv) or (v), and (vii) passing a flotation gas into the aqueous suspension formed in step (vi) to obtain a phase comprising water and a froth comprising clay and ink, and (viii) separating the froth as obtained in step (vii) from the water.

16. The process according to claim 15, wherein the at least one collector agent is selected from the group consisting of modified poylethyleneimines, active and hydrophobic tensides, preferably xanthate or thio phosphates, alkyl sulphates, polyalkylenimines, primary amines, tertiary amines, quaternary amines, fatty amines, esterquats, polyesterquats, and imidazolines or quaternary imidazolium compounds, preferably quaternary imidazolium methosulphates, and most preferred are modified polyethyleneimines.

17. The process according to claim 15, wherein the content of the at least one collector agent is in the range from 0.001 to 50 wt.-% based on the total weight of the solids in the aqueous suspension as provided in step (iii) or (iv), preferably from 0.002 to 20 wt.-% based on the total weight of weight of the clay particles and optional other fillers, more preferably in the range from 0.05 to 0.8 wt.-% based on the total weight of the weight of the solids in the aqueous suspension as provided in step (iii) or (iv) and most preferably in the range from 0.02 to 0.1 wt.-%, based on the total weight of the weight of the solids in the aqueous suspension as provided in step (iii) or (iv).

Description

EXPERIMENTAL SECTION

[0136] The scope and interest of the invention may be better understood on basis of the following examples which are intended to illustrate embodiments of the present invention. However, they are not to be construed to limit the scope of the claims in any manner whatsoever.

[0137] 1 Measurement Methods

[0138] In the following, measurement methods implemented in the examples are described.

[0139] IR Spectroscopy

[0140] IR spectra of powders were measured on a Perkin-Elmer spectrometer with a universal ATR sampling accessory.

[0141] UV-VIS Spectroscopy

[0142] UV-VIS spectra of aqueous solutions/suspensions were recorded at room temperature on a Lambda 2 UV/Vis spectrometer (Perkin-Elmer, USA, scan speed 240 nm/min) using a Perkin-Elmer UV-Vis cell (light path=10 mm).

[0143] Spectrophotometric Colour Evaluation

[0144] The spectrophotometric colour evaluation was carried out using a Techkon SP810 Lambda spectrophotometer (measurement mode: D2 CMYK, DinE, Illuminant: D65, observer: 10)

[0145] Solids Content

[0146] The suspension solids content (also known as dry weight) was determined using a Moisture Analyser MJ33 (Mettler-Toledo, Switzerland), with the following settings: drying temperature of 150 C., automatic switch off if the mass does not change more than 1 mg over a period of 30 s, standard drying of 1 to 10 g of suspension.

[0147] Ash Content

[0148] The ash content in wt.-% based on the total weight of the sample, was determined by incineration of a sample in an incineration crucible which was put into an incineration furnace at 570 C. for 2 hours. The ash content was measured as the total amount of remaining inorganic residues.

[0149] TGA

[0150] Thermogravimetric analysis (TGA) was performed using a Mettler Toledo TGA/DSC1 STARe system based on a sample of 5 to 500 mg and scanning temperatures from 30 to 1 000 C. at a rate of 25 C./minute, under an air flow of 80 mL/min and a nitrogen gas flow of 20 ml/min for balance protection.

[0151] X-Ray Fluorescence Analysis (XRF)

[0152] For carrying out the XRF-measurement the samples were grinded to fine powder and then put into a plastic cassette on a 6 m spectrolene film. The elemental composition of the sample was analysed under helium by sequential, wavelength dispersive X-ray fluorescence (using an ARL PERFORM'X X-ray fluorescence spectrometer, Thermo Fisher Scientific, Inc., USA). The calculation of the elements was made by means of semi-quantitative calibration (UNIQUANT).

[0153] pH

[0154] pH was measured on a Mettler-Toledo Seven-Multi device. The pH of a suspension was measured at 24 C.3 C. using a Mettler Toledo Seven Easy pH meter and a Mettler Toledo InLab Expert Pro pH electrode (Mettler Toledo, Switzerland). A three point calibration (according to the segment method) of the instrument was first made using commercially available buffer solutions having pH values of 4, 7 and 10 at 20 C. (from Aldrich). The reported pH values are the endpoint values detected by the instrument (the endpoint is when the measured signal differs by less than 0.1 mV from the average over the last 6 s).

[0155] Ink Layer Thickness

[0156] The thickness of the ink layer was evaluated by light microscope. The micrographs were taken under light microscope using transmitted light and the brightfield method was applied to get a proper illumination of the sample. The thickness of the ink layer was measured at 4 different spots on each image. The size of the pixel was 0.13 m.

[0157] 2 Paper Preparation

[0158] The tap water used in the following trials contained 15 ppm sodium ions.

[0159] 2.1 Preparation of Coating Compositions

[0160] Coating Composition 1: Ca-Exchanged Bentonite Coating Composition

[0161] A Ca-exchanged bentonite coating colour was prepared from Na-Bentonite (Optigel CK, Rockwood additives) for use in the coating composition according to Table 1.

TABLE-US-00001 TABLE 1 Coating composition 1 (=CC1), (Ca-exchanged bentonite coating composition). parts dry w/w % based on Compound (tradename/supplier) 100 parts by weight of clay Bentonite (Optigel CK, Rockwood 100 additives) Carboxy Methyl Cellulose 1.6 (Finnfix 10, CP, Kelco)

[0162] A 3 wt.-% solids content sodium form of bentonite was prepared. The bentonite was first dispersed in tap water (38 C.), to aid the swelling of the tactoids. Additional sodium hydroxide was added to obtain a pH of 11. The mixture was stirred for 15 minutes to produce an even consistency. In the resulting gel form the dispersed bentonite platelets are surrounded by Na.sup.+ ions. The gel was allowed to age overnight (18 h) to avoid further post makedown thickening. To initiate the calcium ion exchange effect, calcium chloride was added. When adding Ca.sup.2+ ions to the mixture, an intercalation between the bentonite platelets occurs. When adding calcium chloride step by step, the gel finally collapsed and it became fluid. This phenomenon occurred when the pH was between 8 and 9. The fluid bentonite was filtered under vacuum using blue ribbon 589/3 (<2 m) filter paper to increase the solids content (8.5 to 12.0 wt.-%). The bentonite was rinsed with tap water during this process. In preparing the coating composition Carboxy Methyl Cellulose with 10 wt.-% dry solids content was added to re-thicken the mixture. The shade of the obtained coating colour was off-white-grey, and reflects the non-optimal light scattering cross-section of the bentonite in water. The final solids content was 7.1 wt.-%.

[0163] Coating Composition 2: GCC Colour for Top Coating

TABLE-US-00002 TABLE 2 Coating composition 2 (=CC2). Amount (solids content/parts per hundred based on 100 parts Compound (tradename/supplier) by weight of pigment) GCC (Hydrocarb 95, Omya) 77.9 wt.-%/100 Polyvinyl alcohol 25 wt.-%/0.2 Binder (Styronal D628/BASF) 60 wt.-%/9 Thickening agent 24 wt.-%/0.4 (Rheocarb 131/Arkema) Optical brightening agent 100 wt.-%/0.5 (OBA-APA/Tetra Sulpho) Water has been added to adjust the solids content to 47.8 wt.-%.

[0164] To obtain coating composition 2, polyvinylalcohol, Styronal D628, Rheocarb 131 and OBA-APA/Tetra Sulpho were successively added to a GCC slurry, and homogenized at room temperature with a Pendraulik LD50 high speed disperser (50 mm diam. dispersing disc, speed approx. 1 250 rpm) for 2 to 5 minutes after each component had been added.

[0165] 2.2 Preparation of Coated Papers

[0166] Paper 1 is a commercially available A4 copy-grade paper (Cento Plus, 80 g/m.sup.2, uncoated)

[0167] Paper 2 is a SAPPI pre-coated with ground calcium carbonate A4 paper (100% GCC pre-coating)

[0168] Paper 3 is an uncoated copy-grade paper (80 g/m2, paper 1) coated with coating composition 1 on a C-Coater (coater speed 3, rod type 5), coating weight FS: 3.6 g/m.sup.2

[0169] Paper 4 is a SAPPI GCC pre-coated paper (paper 2) coated with composition 1 on a C-Coater (coater speed 3, rod type 5), and then cut to A4 format, coating weight FS: 3.9 g/m.sup.2

[0170] Paper 5 is paper 3, which was further coated with coating composition 2 on a C-Coater (coater speed 3, rod type 3), and then cut to A4 format, coating weight FS: 8.5 g/m.sup.2

[0171] 2.3 Paper Printing [0172] Two inkjet printing systems were used: Canon Pixma iP4850 (Chromalife 100 dye-based ink; print head system Bubble Jet, thermal InkJet; print head: Fine Print Head 1 pl, 512 nozzle k,Y,PBK+1536 nozzle c,m; print settings: standard, high resolution paper; Print resolution: 9 6002 400 dpiHP OfficeJet Pro 8000 Enterprise (Pigment-based ink; print head system Bubble Jet, thermal InkJet; print head: 2 Printhead 2112 nozzle; print settings: normal, optimal; Print resolution: 4 8001 200 dpi)

[0173] In addition, offset printing was done on an ISIT system (printing of 21021 mm.sup.2 bands) with a Skinnex cyan ink.

[0174] Format 1 is 185288 mm.sup.2 rectangle printout in cyan colour on an A4 paper sheet for a total printed area of 532.8 cm.sup.2.

[0175] Format 2 is an arrangement of 6 cyan rectangle printouts (2495 mm.sup.2), 6 Magenta rectangle printouts (2495 mm.sup.2), and 5 black rectangle printouts (24190 mm.sup.2) on a A4 paper sheet for a total printed area of 501.6 cm.sup.2.

[0176] Format 3 is composed of 7 printed strips (ca. 21021 mm.sup.2, printed with Skinnex cyan ink).

TABLE-US-00003 TABLE 3 Overview printed papers. No. Sample Paper Coating Coating Coating Printing of ink ref used layer 1 layer 2 layer 3 Ink type format layers Printed Paper CC2 Pigment Format 1 paper 6 2 2 Printed Paper CC2 Dye Format 1 paper 7 2 2 Printed Paper CC2 Pigment Format 3 paper 8 2 2 Printed Paper CC2 Offset Format 3 paper 9 2 3 Printed Paper CC2 CC1 Pigment Format 1 paper 10 4 1 Printed Paper CC2 CC1 Pigment Format 1 paper 11 4 2 Printed Paper CC2 CC1 Offset Format 1 paper 12 4 3 Printed Paper CC2 CC1 Pigment Format 3 paper 13 4 1 Printed Paper CC2 CC1 Pigment Format 3 paper 14 4 2 Printed Paper CC2 CC1 Offset Format 3 paper 15 4 3 Printed Paper CC2 CC1 CC2 Pigment Format 1 paper 16 5 2 Printed Paper CC2 CC1 CC2 Dye Format 1 paper 17 5 2

[0177] Printing of Paper 9

[0178] The paper used was an 80 g/m.sup.2 SAPPI pre-coated (GCC) paper, which was printed on the ISIT (Ink surface interaction tester) with an offset ink (3 times). 1 sheet of paper 2 was cut in 7 paper bands, and printed on the ISIT with cyan offset ink (3 times, 1 h drying time between two successive layers).

[0179] Printing of Paper 13

[0180] The paper was printed with inkjet pigment ink on format 1 and then left to dry for 10 minutes. Afterwards the printing was performed again on top of the 1.sup.st layer, and, after 10 minutes drying, a 3.sup.rd ink layer was printed.

[0181] Printing of Paper 14

[0182] The paper was printed with inkjet pigment ink on format 2, then left to dry for 10 minutes. The printing was then performed again on top of the 1.sup.st layer, and, after 10 minutes drying, a 3.sup.rd ink layer was printed.

[0183] Printing of Paper 15

[0184] The paper used was a SAPPI pre-coated (GCC) paper, which was coated with a bentonite layer and printed on the ISIT (Ink surface interaction tester) with an offset ink (3 times).

[0185] 1 A4 sheet of paper was cut vertically in 7 pieces, and printed on the ISIT with cyan offset ink (Novavit 4800 SKINNEX Cyan, 3 consecutive printed layers on top of each other, 1 h drying time between two successive layers).

[0186] 3 Deinking and Floatation with Pigmented Ink

[0187] The tap water used in the following trials contained 15 ppm sodium ions. The modified polyethyleneimine polymer that has been used in the following trials has a polyethyleneimine backbone with a molecular weight (M.sub.w) of 5 000 g/mol and is modified with a saturated C5 fatty acid as described in EP 2 366 456 A1.

Example 1: Deinking and Flotation of Printed Paper 11 (Inventive Example)

[0188] Step A): Ink Desorption from Paper

[0189] One A4 printed paper 11 sheet was dipped in a beaker (5 L) in 2.2 L deionized water and was left to stay without particular stirring during 10 minutes. The ink slipped from the sheet in large particles and the black colour was completely removed, whereas blue and red schemes leave slightly red/pink colour traces on the paper. Afterwards, the decolourized paper was removed from the beaker and the water with ink particles in suspension were directly used for flotation purification. The pH of the obtained mixture was 9.1.

[0190] Step B): Purification by Flotation

[0191] Flotation was performed on an Outotec Labcell flotation device. 2 L of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min). A pink/purple coloured foam appeared, and the water suspension became clearer after 2 minutes. After that period of time, the water sample was visually free from coloured particles. The flotation was stopped, and the different fractions (removed foam and clean water) were analysed.

[0192] Waste (removed foam fraction): dark purple, V=250 ml, pH=8.3 Clean water: colourless with trace amount of particles in suspension, V=1.75 l, pH=8.3.

[0193] Step C: Filtration

[0194] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 80 mg of a dark powder were recovered and analysed.

[0195] Analyses

[0196] IR

[0197] The waste fraction showed a Peak at 1 000 cm.sup.1 that can be attributed to the bentonite (SiO bond, see FIG. 1).

[0198] UV/Vis

[0199] FIG. 2 shows the UV-vis spectra of the aqueous suspension before and after the flotation (once filtered).

[0200] Spectrophotometry

[0201] Cyan density was measured on the blue-printed portions

[0202] Magenta density was measured on the red-printed portions

[0203] Black density was measured on the black-printed portions

[0204] Given values are an average of 10 measurements.

TABLE-US-00004 TABLE 4 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 1/Printed paper 11 before step A 1.3321 1.299 1.5475 Example 1/Printed paper 11 after step A 0.0264 0.1018 0.0231

[0205] Composition Analysis

[0206] The compositions of the different fractions of materials were analysed using the following techniques: [0207] Determination of the ash content [0208] Thermogravimetric analysis [0209] Semiquantitative XRF-analysis (UNIQUANT) [0210] FTIR-spectra

[0211] The results are summarized in Tables 5 and 6 below.

TABLE-US-00005 TABLE 5 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 11 31.0 Mainly paper (cellulose), ash before step A contains mainly CaCO.sub.3 (25 wt.-%), Al-silicates (5 wt.-%) Printed paper 11 30.4 Mainly paper (cellulose), ash after step A contains mainly CaCO.sub.3 (26 wt.-%), some Al-silicates (4 wt.-%) Waste collected 57 Mainly inorganics, especially after step B flotation Al-Silicates (45 wt.-%), CaCO.sub.3 (10 wt.-%)

TABLE-US-00006 TABLE 6 Composition of different fractions. Printed Printed Waste collected paper 11 paper 11 after step B before step A after step A flotation CaO 13.9 wt.-% 13.7 wt.-% 2.95 wt.-% MgO 0.95 wt.-% 0.91 wt.-% 2.75 wt.-% Al.sub.2O.sub.3 1.38 wt.-% 1.13 wt.-% 9.45 wt.-% SiO.sub.2 3.38 wt.-% 2.42 wt.-% 32.6 wt.-% Fe.sub.2O.sub.3 0.25 wt.-% 0.11 wt.-% 1.57 wt.-% TiO.sub.2 0.04 wt.-% 0.02 wt.-% 0.14 wt.-% SO.sub.3 0.06 wt.-% 0.04 wt.-% 0.18 wt.-% Na.sub.2O 0.20 wt.-% 0.21 wt.-% Others 0.08 wt.-% 0.10 wt.-% 0.05 wt.-% TGA 30-250 C. 0.17 wt.-% 0.14 wt.-% 7.0 wt.-% (.fwdarw.water) TGA 250-1000 C. 10.54 wt.-% 11.74 wt.-% (.fwdarw.CO.sub.2) Organic content 69.0 wt.-% 69.6 wt.-% 43 wt.-%

Example 2: Deinking and Flotation of Printed Paper 16 (Inventive Example)

[0212] Step A): Ink Desorption from Paper

[0213] One A4 printed paper 16 sheet was dipped in a beaker (5 l) in 2.2 l deionised water and was left to stay without particular stirring during 10 minutes. The ink slipped from the sheet in very large platelets and the black colour was completely removed, whereas blue and red schemes leave slightly red/pink colour traces on the paper. Afterwards, the decolourized paper was removed from the beaker and the water with ink particles in suspension (slightly red in colour and trouble aspects) were directly used for flotation purification. The pH of the obtained mixture was 9.1.

[0214] Step B): Purification by Flotation

[0215] Flotation was performed on an Outotec Labcell flotation device. 21 of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min). A pink/purple coloured foam comprising pink/purple ink particles appeared. Rapid decolourization of the water sample was observed, but lots of ink particles remain in suspension. Another 0.5 g of the modified polyethyleneimine polymer were added, which lead to formation of a colourless foam with ink particles on the surface. After 20 minutes, no more ink particle were observed at the surface. The flotation was stopped, and the different fractions (removed foam and clean water) were analysed. Waste (removed foam fraction): dark purple, V=200 ml, pH=8.5

[0216] Clean water: colourless with traces of small ink particles remaining in suspension, V=1.81, pH=8.3.

[0217] Step C: Filtration

[0218] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 0.9 g of purple/multicolour particles were recovered and analysed.

[0219] Analyses

[0220] IR

[0221] The waste fraction showed a Peak at 1 000 cm.sup.1 that can be attributed to the bentonite (SiO bond, see FIG. 3) and a peak at 1 400 cm.sup.1 that can be attributed to calcium carbonate.

[0222] UV/Vis

[0223] FIG. 4 shows the UV-vis spectra of the aqueous suspension before and after the flotation (once filtered).

[0224] Spectrophotometry

[0225] Cyan density was measured on the blue-printed portions

[0226] Magenta density was measured on the red-printed portions

[0227] Black density was measured on the black-printed portions

[0228] Given values are an average of 10 measurements.

TABLE-US-00007 TABLE 7 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 2/Printed paper 16 before step A 1.6269 1.569 1.6735 Example 2/Printed paper 16 after step A 0.0292 0.0917 0.0468

[0229] Composition Analysis:

TABLE-US-00008 TABLE 8 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 16 36.8 Mainly paper (cellulose), 30 wt.-% before step A CaCO.sub.3, 6 wt.-% Al-Silicates, coating binder Printed paper 16 29.7 Mainly paper (cellulose), about after step A 26 wt.-% CaCO.sub.3, 4% Al-Silicates, coating binder Waste collected 85.2 Mainly inorganic, most of it (>60%) after step B flotation CaCO.sub.3, 20 wt.-% Al-Silicate

TABLE-US-00009 TABLE 9 Composition of different fractions. Printed Printed Waste collected paper 16 paper 16 after step B before step A after step A flotation CaO 18.7 wt.-% 14.5 wt.-% 34.0 wt.-% MgO 0.98 wt.-% 0.92 wt.-% 1.48 wt.-% Al.sub.2O.sub.3 0.96 wt.-% 0.88 wt.-% 3.33 wt.-% SiO.sub.2 2.31 wt.-% 1.65 wt.-% 10.6 wt.-% Fe.sub.2O.sub.3 0.22 wt.-% 0.10 wt.-% 0.47 wt.-% TiO.sub.2 0.03 wt.-% 0.02 wt.-% 0.05 wt.-% SO.sub.3 0.07 wt.-% 0.05 wt.-% 0.07 wt.-% Na.sub.2O Others 0.15 wt.-% 0.08 wt.-% 0.22 wt.-% TGA 30-250 C. 0.16 wt.-% 0.19 wt.-% 35.0 wt.-% (.fwdarw.water) TGA 250- 1000 C. 13.20 wt.-% 11.31 wt.-% (.fwdarw.CO.sub.2) Organic content 63.2 wt.-% 70.3 wt.-% 14.7 wt.-%

Example 3: Deinking and Flotation of Printed Paper 6 (Comparative Example)

[0230] Step A): Ink Desorption from Paper

[0231] One A4 printed paper 16 sheet was dipped in a beaker (5 l) 2.2 l tap water and was left to stay without particular stirring during 10 minutes. No visible particles were released in the tap water, and no decolourization of the paper was observed. Only a slight pink colourization of water was observed.

[0232] Spectrophotometry

[0233] Cyan density was measured on the blue-printed portions

[0234] Magenta density was measured on the red-printed portions

[0235] Black density was measured on the black-printed portions

[0236] Given values are an average of 10 measurements.

TABLE-US-00010 TABLE 10 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 3/Printed paper 6 before step A 1.345 1.2581 1.5618 Example 3/Printed paper 6 after step A 1.2585 1.151 1.5339

Example 4: Deinking and Flotation of Printed Paper 13 (Inventive Example)

[0237] Step A): Ink Desorption from Paper

[0238] One A4 printed paper 13 sheet was dipped in a beaker (5 l) in 2.2 l tap water. The mixture was regularly agitated during 10 minutes. The ink slipped slowly from the sheet in small platelets and the black colour was completely removed, whereas blue and red schemes leave slightly red/pink colour traces on the paper. Afterwards, the decolourized paper was removed from the beaker and the water with ink particles in suspension (slightly purple in colour and trouble aspect) were directly used for flotation purification. The pH of the obtained mixture was 7.9.

[0239] Step B): Purification by Flotation

[0240] Flotation was performed on an Outotec Labcell flotation device. 21 of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (0.8 g, 11.0 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min). A pink/purple coloured foam comprising pink/purple with large ink particles appeared. Rapid decolourization of the water sample was observed, but visible ink particles remain in suspension. Another 0.4 g of the modified polyethyleneimine polymer were added, which lead to formation of a colourless foam with ink particles on the surface. After 10 minutes complete decolourization occurred. The flotation was stopped, and the different fractions (removed foam and clean water) were analysed.

[0241] Waste (removed foam fraction): dark purple, V=300 ml, pH=8.2

[0242] Clean water: colourless, no significant amount of particles present, V=1.7 l, pH=8.0.

[0243] Step C: Filtration

[0244] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 0.28 g of purple/colour particles were recovered and analysed.

[0245] Analyses

[0246] IR

[0247] The waste fraction showed a Peak around 1 000 cm.sup.1 that can be attributed to the bentonite (SiO bond, see FIG. 5) and a peak around 1 400 cm-1 that can be attributed to calcium carbonate.

[0248] UV/Vis

[0249] FIG. 6 shows the UV-vis spectra of the aqueous suspension before and after the flotation.

[0250] Spectrophotometry

[0251] Cyan density was measured on the blue-printed portions

TABLE-US-00011 TABLE 11 Results of spectrophotometric evaluation. Sample Cyan Example 4/Printed paper 13 before step A 1.5672 Example 4/Printed paper 13 after step A 0.0673

[0252] Ink Layer Thickness:

TABLE-US-00012 TABLE 12 Ink layer thickness before and after exposure to water. Average Standard deviation Sample thickness (m) (m) Printed paper 13 before 3.5 1.1 exposure to water Printed paper 13 after no ink visible exposure to water Printed paper 10 before 1.9 0.7 exposure to water Printed paper 10 after no ink visible exposure to water

[0253] Composition Analysis:

TABLE-US-00013 TABLE 13 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 13 30.2 Mainly paper (cellulose), 25 wt.-% before step A CaCO.sub.3, 5 wt.-% Al-Silicates Printed paper 13 44.9 Mainly inorganics, especially after step A Al-silicates (30 wt.-%) and CaCO.sub.3 (15 wt.-%)

TABLE-US-00014 TABLE 14 Composition of different fractions. Printed paper 13 Printed paper 13 before step A after step A CaO 13.26 wt.-% 7.04 wt.-% MgO 1.00 wt.-% 1.88 wt.-% Al.sub.2O.sub.3 1.20 wt.-% 6.00 wt.-% SiO.sub.2 2.60 wt.-% 20.12 wt.-% Fe.sub.2O.sub.3 0.09 wt.-% 0.82 wt.-% TiO.sub.2 0.02 wt.-% 0.08 wt.-% SO.sub.3 0.04 wt.-% 0.14 wt.-% Na.sub.2O 0.06 wt.-% 0.40 wt.-% Others 0.07 wt.-% 0.17 wt.-% TGA 30-250 C. 0.24 wt.-% 1.59 wt.-% (.fwdarw.water) TGA 250-1000 C. 11.63 wt.-% 6.66 wt.-% (.fwdarw.CO.sub.2) Organic content 69.8 wt.-% 55.1 wt.-%

Example 5: Deinking and Flotation of Printed Paper 14 (Inventive Example)

[0254] Step A): Ink Desorption from Paper

[0255] One A4 printed paper 14 sheet was dipped in a beaker (5 l) in 2.2 l tap water. The mixture was regularly agitated during 10 minutes. The ink slipped slowly from the sheet in small particles, pink colour traces remained on the paper from blue and especially from red printed areas. Afterwards, the decolourized paper was removed from the beaker and the water with ink particles in suspension was directly used for flotation purification. The pH of the obtained mixture was 7.4.

[0256] Step B): Purification by Flotation

[0257] Flotation was performed on an Outotec Labcell flotation device. 2 L of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (0.8 g, 11.0 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 20 minutes (4 to 6 l/min). A pink/purple coloured foam comprising pink/purple with large ink particles appeared. Rapid decolourization of the water sample was observed, but visible ink particles remain in suspension. After 10 minutes another 0.6 g of the modified polyethyleneimine polymer were added, which lead to formation of a colourless foam with ink particles on the surface. After 10 minutes complete decolourization occurred, although some tiny dark particles (black) of ink remain in suspension. The flotation was stopped, and the different fractions (removed foam and clean water) were analysed.

[0258] Waste (removed foam fraction): dark purple, V=300 ml, pH=8.2

[0259] Clean water: colourless, no significant amount of particles present, V=1.7 l, pH=8.0.

[0260] Step C: Filtration

[0261] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 0.26 g of purple/colour particles were recovered and analysed.

[0262] Analyses

[0263] IR

[0264] The waste fraction showed a Peak at 1 000 cm.sup.1 that can be attributed to the bentonite (SiO bond), (FIG. 7).

[0265] Spectrophotometry

[0266] Cyan density was measured on the blue-printed portions

[0267] Magenta density was measured on the red-printed portions

[0268] Black density was measured on the black-printed portions

[0269] Given values are an average of 10 measurements.

TABLE-US-00015 TABLE 15 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 5/Printed paper 1.55 1.52 (1.64 on blue sections) 1.66 14 before step A Example 5/Printed paper 0.084 0.267 (0.206 on blue sections) 0.061 14 after step A

[0270] Composition Analysis

TABLE-US-00016 TABLE 16 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Waste collected after 46.6 Mainly organics (Cellulose), step B flotation 31 wt.-% CaCO.sub.3, 12 wt.-% Al-silicate

TABLE-US-00017 TABLE 17 Composition of different fractions. Waste collected after step B flotation CaO 4.34 wt.-% MgO 2.13 wt.-% Al.sub.2O.sub.3 7.02 wt.-% SiO.sub.2 23.75 wt.-% Fe.sub.2O.sub.3 0.89 wt.-% TiO.sub.2 0.08 wt.-% SO.sub.3 0.16 wt.-% Na.sub.2O 0.33 wt.-% Others 0.27 wt.-% TGA 30-250 C. 2.42 wt.-% (.fwdarw.water) TGA 250-1000 C. 5.17 wt.-% (.fwdarw.CO.sub.2) Organic content 53.4 wt.-%

Example 6: Deinking and Flotation of Printed Paper 6 (Comparative Example)

[0271] Step A): Ink Desorption from Paper:

[0272] One A4 printed paper 6 sheet is dipped in 21 deionized water and left to stay without particular stirring during 10 minutes. No visible particles are released in water, and the paper does not decolourize. Only a slight pink colourization of water can be observed.

[0273] Spectrophotometry for Colour Evaluation:

[0274] Cyan density was measured on the blue-printed portions

[0275] Magenta density was measured on the red-printed portions

[0276] Black density was measured on the black-printed portions

TABLE-US-00018 TABLE 18 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 6/Printed paper 6 before step A 1.345 1.2581 1.5618 Example 6/Printed paper 6 after step A 1.2585 1.151 1.5339

Example 7: Deinking and Flotation of Printed Paper 8 (Comparative Example)

[0277] Step A): Ink Desorption from Paper

[0278] One A4 printed paper 8 sheet was dipped in a beaker (5 l) in 2 l tap water and manually agitated regularly for 10 minutes. Almost no visible particles are released in water and the paper does not decolourize. Only a slight pink colourization of the tap water was observed. Afterwards, the paper sheet was removed from the beaker and the colour density measured on each section.

[0279] Spectrophotometry for Colour Evaluation

[0280] Cyan density was measured on the blue-printed portions

[0281] Magenta density was measured on the red-printed portions

[0282] Black density was measured on the black-printed portions

[0283] Given values are an average of 10 measurements.

TABLE-US-00019 TABLE 19 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 7/Printed paper 8 before step A 1.59 1.57 1.64 Example 7/Printed paper 8 after step A 1.41 1.36 1.43

Example 8: Deinking and Flotation of Printed Paper 17 (Inventive Example)

[0284] Step A): Ink Desorption from Paper

[0285] One A4 printed paper 17 sheet was dipped in a beaker (5 l) in 2.2 l deionized water and was left to stay without particular stirring for 1 h. Some ink dissolved (blue colouration) and particles slipped from the sheet. After another 1 hour, the decolourized paper was removed from the beaker and colour traces can still be seen on the paper surface. The water (deep blue in colour) with ink particles in suspension (the particles sedimented rapidly) was directly used for flotation purification. The pH of the obtained mixture was 8.1.

[0286] Step B): Purification by Flotation

[0287] Flotation was performed on an Outotec Labcell flotation device. 21 of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min). A dark particles containing foam appeared, after 10 minutes reduced foaming was observed, although the sample remained quite coloured. Another 1 g (7.5 wt.-% solid content) of the modified polyethyleneimine polymer were added and the flotation was continued for another 10 minutes. Complete decolourization of the sample occurred, the sample was visually free from coloured particles but some trace amount of white particles remained in the suspension. The flotation was stopped, and the different fractions (removed foam and clean water) were analysed.

[0288] Waste (removed foam fraction): dark purple, V=300 ml, pH=8.3

[0289] Clean water: colourless, no significant amount of particles present, V=1.7 l, pH=7.6

[0290] Step C: Filtration

[0291] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 0.39 g of a grey powder were recovered and analysed.

[0292] Analyses

[0293] IR

[0294] The waste fraction showed a Peak at 1 000 cm.sup.1 that can be attributed to the bentonite (SiO bond, see FIG. 8) and a peak at 1 400 cm.sup.1 that can be attributed to calcium carbonate.

[0295] UV/Vis

[0296] FIG. 9 shows the UV-vis spectra of the aqueous suspension before and after the flotation.

[0297] Spectrophotometry

[0298] Cyan density was measured on the blue-printed portions

[0299] Magenta density was measured on the red-printed portions

[0300] Black density was measured on the black-printed portions

[0301] Given values are an average of 10 measurements.

TABLE-US-00020 TABLE 20 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 8/Printed paper 17 before step A 1.2388 0.9301 1.0467 Example 8/Printed paper 17 after step A 0.163 0.2073 0.2387

[0302] Composition Analysis

TABLE-US-00021 TABLE 21 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 17 30.1 Mainly coated paper (cellulose) & before step A coating binders, 27 wt.-% CaCO.sub.3, 3 wt.-% Al-Silicates Flotation waste 67.5 43 wt.-% CaCO.sub.3 and 26 wt.-% after step B Al-Silicates, organic polymers

TABLE-US-00022 TABLE 22 Composition of different fractions. Printed paper 17 Flotation waste after before step A step B CaO 14.1 wt.-% 22.8 wt.-% MgO 0.95 wt.-% 1.54 wt.-% Al.sub.2O.sub.3 0.93 wt.-% 4.28 wt.-% SiO.sub.2 1.78 wt.-% 15.3 wt.-% Fe.sub.2O.sub.3 0.09 wt.-% 0.81 wt.-% TiO.sub.2 0.02 wt.-% 0.08 wt.-% SO.sub.3 0.04 wt.-% 0.93 wt.-% Na.sub.2O Others 0.11 wt.-% 0.42 wt.-% TGA 30-250 C. 0.15 wt.-% 1.28 wt.-% (.fwdarw.water) TGA 250-1000 C. 11.93 wt.-% 20.07 wt.-% (.fwdarw.CO.sub.2) Organic content 69.9 wt.-% 32.5 wt.-%

Example 9: Deinking and Flotation of Printed Paper 7 (Comparative Example)

[0303] Step A): Ink Desorption from Paper

[0304] One A4 printed paper 7 sheet was dipped in a beaker (5 l) in 2.2 l deionized water and was left to stay without particular stirring for 1 h. Some ink dissolved and particles got into the water (dissolution and suspension). After another 1 hour, the decolourized paper was removed from the beaker and colour traces can still be seen on the paper surface. The water (deep blue in colour) with ink particles in suspension (the particles sedimented rapidly) was directly used for flotation purification. The pH of the obtained mixture was 7.9.

[0305] Step B): Purification by Flotation

[0306] Flotation was performed on an Outotec Labcell flotation device. 2 L of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (1.0 g, 7.5 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min). A dark particles containing foam appeared, after 10 minutes reduced foaming was observed, although the sample remained quite coloured. Another 1 g (7.5 wt.-% solid content) of the modified polyethyleneimine polymer were added and the flotation was continued for another 10 minutes. After that time the water sample was almost colourless (slight blue colour). The flotation was stopped, and the different fractions (removed foam and clean water) were analysed.

[0307] Waste (removed foam fraction): dark purple, V=200 ml, pH=7.3

[0308] Clean water: colourless, no significant amount of particles present, V=1.8 l, pH=7.2.

[0309] Analyses

[0310] Spectrophotometry

[0311] Cyan density was measured on the blue-printed portions

[0312] Magenta density was measured on the red-printed portions

[0313] Black density was measured on the black-printed portions

[0314] Given values are an average of 10 measurements.

TABLE-US-00023 TABLE 23 Results of spectrophotometric evaluation. Sample Cyan Magenta Black Example 9/Printed paper 7 before step A 1.0821 0.7461 1.028 Example 9/Printed paper 7 after step A 0.2254 0.2739 0.3384

[0315] Composition Analysis

TABLE-US-00024 TABLE 24 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 7 after 28.7 Mainly coated paper (cellulose) and step A coating binders, 27 wt.-% CaCO.sub.3, 2.5 wt.-% Al-Silicates

TABLE-US-00025 TABLE 25 Composition of different fractions. Printed paper 7 after step A CaO 15.0 wt.-% MgO 0.95 wt.-% Al.sub.2O.sub.3 0.75 wt.-% SiO.sub.2 1.22 wt.-% Fe.sub.2O.sub.3 0.07 wt.-% TiO.sub.2 0.02 wt.-% SO.sub.3 0.06 wt.-% Na.sub.2O Others 0.13 wt.-% TGA 30-250 C. 0.10 wt.-% (.fwdarw.water) TGA 250-1000 C. 12.71 wt.-% (.fwdarw.CO.sub.2) Organic content 69.0 wt.-%

Example 10: Deinking and Flotation of Paper 15 (Inventive Example)

[0316] Step A): Ink Desorption from Paper

[0317] One A4 printed paper 15 sheet was dipped in a beaker (5 l) in 2.2 l tap water and was left to stay without particular stirring for 1 h. The paper was relatively hydrophobic and ink went off after paper was really wet and manual agitation was required to remove the ink layer. After 10 minutes the decolourized paper was removed from the beaker and the coloured water with dispersed ink particles was directly used for flotation purification. The pH of the obtained mixture was 7.4.

[0318] Step B): Purification by Flotation

[0319] Flotation was performed on an Outotec Labcell flotation device. 21 of the aqueous suspension obtained in step A) were placed in the flotation flask. The mixture was stirred for 2 minutes under air flow (55 Hz, 1 650 rpm, air flow: 4 to 6 l/min). After that period of time, a modified polyethyleneimine polymer (0.8 g, 11 wt.-% solid content) was added. The air flow was stopped and the mixture was stirred for additional 2 minutes. The air flow was then turned on for 10 minutes (4 to 6 l/min). An almost colourless foam appeared containing the blue ink particles. Another 0.6 g (7.5 wt.-% solid content) of the modified polyethyleneimine polymer were added and the flotation was continued for another 10 minutes. After that time the water sample was almost colourless and free from particles. The flotation was stopped after a total time of 20 minutes, and the different fractions (removed foam and clean water) were analysed.

[0320] Waste (removed foam fraction): blue-coloured water and particles, V=300 ml, pH=8.1

[0321] Clean water: colourless, no significant amount of particles present, V=1.7 l, pH=8.1.

[0322] Step C: Filtration

[0323] The waste fraction was filtered by using a Buchner funnel (Whatman grade 589/3 qualitative filtration paper), washed with deionized water and dried under reduced pressure at 90 C. for 4 h. 0.25 g of blue and white particles were recovered and analysed. The clean fraction from the flotation was also filtered and no residue was collected on filter.

[0324] IR

[0325] The waste fraction showed a Peak at 1 000 cm.sup.1 that can be attributed to the bentonite (FIG. 10).

[0326] Spectrophotometry

[0327] Cyan density was measured on the blue-printed portions

[0328] Given values are an average of 10 measurements.

TABLE-US-00026 TABLE 26 Results of spectrophotometric evaluation. Sample Cyan Example 10/Printed paper 15 before step A 1.9468 Example 10/Printed paper 15 after step A 0.0462

[0329] Composition Analyses

TABLE-US-00027 TABLE 27 Composition of different fractions. Ash content Fraction [wt.-%] Composition/Remarks Printed paper 15 28.4 Mainly paper (cellulose), ash contains after step A 25 wt.-% CaCO.sub.3 and 4 wt.-% clay Printed paper 15 45.2 Enrichment of inorganics, contains before step A 10 wt.-% CaCO.sub.3 and 35 wt.-% Al-Silicates

TABLE-US-00028 TABLE 28 Composition of different fractions. Printed paper Waste collected after 15 after step A step B CaO 13.55 wt.-% 6.06 wt.-% MgO 1.00 wt.-% 1.85 wt.-% Al.sub.2O.sub.3 0.86 wt.-% 6.06 wt.-% SiO.sub.2 1.59 wt.-% 22.77 wt.-% Fe.sub.2O.sub.3 0.08 wt.-% 0.84 wt.-% TiO.sub.2 0.02 wt.-% 0.08 wt.-% SO.sub.3 0.04 wt.-% 0.09 wt.-% Na.sub.2O 0.04 wt.-% 0.09 wt.-% Others 0.07 wt.-% 0.30 wt.-% TGA 30-250 C. 0.22 wt.-% 1.66 wt.-% (.fwdarw.water) TGA 250-1000 C. 10.90 wt.-% 5.34 wt.-% (.fwdarw.CO.sub.2) Organic content 71.6 wt.-% 54.8 wt.-%

[0330] Ink Layer Thickness:

TABLE-US-00029 TABLE 29 Ink layer thickness before and after exposure to water. Average Standard deviation Sample thickness (m) (m) Printed paper 15 before 3.8 2.4 exposure to water Printed paper 15 after no ink visible exposure to water Printed paper 12 before 2.6 0.7 exposure to water Printed paper 12 after no ink visible exposure to water

[0331] was measured at 4 different spots on each image. The size of the pixel was 0.13 m.

Example 11: Deinking and Flotation of Paper 9, (Comparative Example)

[0332] Step A): Ink Desorption from Paper

[0333] 6.5 paper bands from paper 9 (dimension 21215 mm.sup.2) were dipped in a beaker (5 l) in 2.2 l tap water and was left to stay without particular stirring for 1 h. The paper was relatively hydrophobic and ink went off after paper was really wet and manual agitation for 10 minutes was required to remove the ink layer. Nothing came off the paper, after 10 minutes the decolourized paper was removed from the beaker. The water was completely clear and all the ink remained on the paper.

[0334] Spectrophotometry

[0335] Cyan density was measured on the blue-printed portions

[0336] Given values are an average of 10 measurements.

TABLE-US-00030 TABLE 30 Results of spectrophotometric evaluation. Sample Cyan Example 11/Printed paper 9 before step A 2.123 Example 11/Printed paper 9 after step A 2.007