Deinking and Reuse of Old Coloured Newsprint
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Journal of Scientific & Industrial Research Vol. 60, August 2001, pp 649-654
Deinking and Reuse of Old Coloured Newsprint
Magda G El-Meligy' and Maha M Ibrahim
Cellulose and Paper Department, National Research Centre, Dokki, Cairo, Egypt
Received: 28 August 2000; accepted: 30 April 2001
Due to increase in paper product requirements and the sources for production gradually decreasing the percentage of deinked newsprint and other grades is expected to increase considerably over the next few years. About 80 per cent of all waste paper comes from three sources: Corrugated boxes, Newspapers, and Office papers. It is also observed that the biggest users of deinked waste paper are newsprint, tissue or other bright grades'.As a result of the technological progress, use of colour in newspaper is becoming increasingly popular. In this work, oxidant acids such as sulphuric or acetic acids however play an important role for disintegrating the coloured materials from the old coloured newsprint in certain condition such as temperature. concentration of acid, and time. The paper produced has satisfactory optical and physical properties but a slight decrease in the mechanical properties, where addition of some additives such as polyvinyl alcohol, new pulp or paper shaving at certain percent- age, improved these properties.
Introduction is affected not only by the amount of ink present but also by the size distribution of the ink particles". Typically, new ink consists of carbon black and a high viscosity mineral oil blended with low-viscosity min- Hayashi" has claimed that both oil absorbency and erai oil to give the desired viscosity but coloured news- opacity of recycled fiber newsprint were lower than those print ink consists of mineral oil blended with pigment of virgin-fiber newsprint. Hayashi also claimed that lower flushes+Deinking of cellulosic materials (e.g. waste oil absorbency meant lower print quality, although this newsprint) is streamlined by dispersing the celIulosic is not always true if the printer and ink maker are pre- material to form a pulp slurry, pulping the dispersed cel- pared for the changes". lulosic material to separate ink from it, and washing the To obtain recycled paper with improved properties, pulp slurry to dispose of the separated ink provided an amine functional polyvinyl alcohol is added as wet-end ionic surfactant is added during dispersing or washing, additive of the paper making process. This increases the a size was added during or subsequent to any of these wet-and the dry-strength properties". steps gave a brightness of 55.5 and no ink specks'.
Using Borol solution (NaHSO, and NaBH ) as a re- Deinking of waste newspaper is carried out with a 4 duction bleaching of the recycled fiber (newsprint, tis- sodium hydroxide, sodium silicate, hydrogen peroxide sue and mixed paper containing household colIection) and 80 per cent esterification product of citric acid and gives 13 per cent higher brightness than standard bright- octahecyla1cohol, thereby giving more bright paper. ness value for the newsprint". Old newspapers are classified into five groups, de- Standard newsprint has a basic weight of 40-56 g/rn? pending on their fiber length. Removal of the short fiber and should have an ISO brightness 58± 2 per cent". (0.2 mm) by flotation was effective for regenerating fi- ber". Experimental Procedure Brightness increased after removal of the ink since Wastepaper Systems the ink has lower brightness than fiber. Pulp brightness The wastepaper processing systems varies according *Author for correspondence to the pulp grade to be produced, e.g., pulps for news- 650 J SC IIND RES VOL 60 AUGUST 2001
print, printing, writing, household paper or I in er board. added in the pulper, soak in g tower to maintain or to in 1 The systems for the first three, consists of a combina crease brig htness' . tion of repulping, deinking, screening, c leanin g, and bleaching process. Relati vely, mild cookin g is sometimes Here, th e deinked pulp was treated with 3 per cent 1 Hp (based on dry weight of the pulp. in the presence carried out as th e first stage of the process' . 1 of 0.05 per cent MgS04 and 0.1 per cent sodium si li Wastepaper Used cate. The temperature of the bleachi ng process was ad justed at70"C and th e pH 9.5 for 30 m in. After bleach The wastepaper used in thi s work was coloured and in g , th e pulps were thoroughl y washed till it became uncoloured newsprints in equal rati os. neutra l. Repulping Hondsheet Formation T he wastepapers are introduced into a pulper togeth er Ta ppi Standard method was u sed to pre pare with hot water and pulped with mechanical agitat ion. hand sheets from deinked and bleached newsprint. Dur Some chemicals such as the deinking agent and NaOH in g sheet formation, some adhesive and fill ers were 1 are often added as pulping additi ves' . added.
In this work, coloured newsprints were cut into small The adhesives used was polyvinyl-alcohol (5 per cent) pieces and soaked in warm water with 0.5 per cent NaOH and th e filler used was talc powder (2 per cent). To in and 0.5 per cent sodium silicate at 50°C for at least 6 h, crease the size ability of the paper rosin size (2 per cent) th en mechanicall y stirred with a stirrer ( 1500 r p m) to (obtain ed from Rakta Co., Al ex) was used togethe r w ith obtain a pulp slurry. a lum ( I 0 per cent) for obtaining pH 4.5. The gram mage used for handsheets formation was 48 g I m1 for news Deinking print. Also, in this work hand sheets of paper were formed The deinking process passed on two stages : e ither from de inked newsprint only or from blended 80 per cent deinked newsprint with 20 perc nt wood pulp Fi rst stage: or 20 per cent paper shavings. T he handsheets conditioned for 24 h at 25"°C and 50 The detachment of ink is initiated during the repulping per cent R H then the tensile strength and tearin g resis stage and the hi gh consistency tance were measured . O ptical properties such as bright pulper has a relatively hi gh ability for in k detachment. ness and o pac it y were also measured.
Second stage: Chemical Analysis of Pulp and Paper
The separation of ink particles liberated from the Cellulose, extractable he mi cellulo. e, li gnin, and ash fiber surface and dispersed in the pulp slurry are re content were analyzed for waste and bleached deinked moved by washin g. The quantities of chemicals charged 10 11 newsprint, according to Tappi standard and ASTM · . in the de inking formulation are calculated based on the oven-dry we ight of the repulping newsprint') Results and Discussion
Different concentration of 2, 3, 5 or I 0 per cent of Chemical Analysis of Old Coloured Newsprint oxidised acids suc h as su lphuric acid or acetic acid in Newsprint was chemicall y analysed for a cellulose, the presence of 0.5 per cent oxalic acid were used as extractible hemicellulose, li gnin and ash content be fore catalyst. After 30 min at 60°C the pulp was washed and afte r bleached de inking. quickly and carefully with water to obtain white pulp. Table I shows that the deinking of the old coloured newsprint increases the a cellul se content but de Bleachinf{ creases the li g nin and extractible hemicellulose, sin ce Since the brightness of wastepaper is often low and the chemicals which are added during deinking process decreases further during storage or throug h the action of may be dissolute li gnin and hemicellulose to some ex r h Pmir::. l..; rlmimr nrocessi ng bleaching chemicals are tent. EL-MELIGY & IBRAH IM : DE l KI NG & RE USE OF OLD COLOURED 1EWSPR I T 651
Tab le !-Chemical analys is or old coloured newsprint before Tabl e 2-Eilect or different oxidants ac id on bri ghtn ess ami and aft er treatment co lour of th e bleac hin g deinked co loured newsprint
Experiment Old co loured Bl eac hin g Experiment Brightness Colour newsprint deinked newsprint a -Cellulose, per cent 59 64.8 Untrea ted pulp 42 Grey Extractable Pulp treat ed wit h 5 per ce nt aceti c acid s
Ash , per cent 1.3 1.1 Pulp treated with 5 per ce nt sulp huri c ac id 57.3 Whit e
Pulp trea ted with I 0 per ce nt Deinking of th e Old Coloured Newsprint sulphuri c acid 58. 1 Wh ite Deinking of the old coloured newsprint was carri ed ou t in three stages : Time or treatm ent : 30 min at 70 "C Soaking wi th sodium hyd rox ide and sod ium sili cate in warm water for 6 h then repulping ahm·t·'25 "(' n·dllltion f-1 .SO 2 Use of ox id ant acid such as sulphuric /or aceti c H 2 So ~ 2 ' 3 . ac id at certain condition. H + 1-1 2S03 so;- + 21-1 3 Bleachin g with hyd rogen peroxide. If th e organometalli c co mpound is R-M. th en R-M +So;- +2 1-1 + ~ M -SO, + R - f-1 Role of Soaking. Sodium Hyd roxide ond Sodium In th e case of aceti c acid + Silicate CH 3 COOH H CH 3COO - + f-1 R- M + CH COO - + H + ~ CH ,,COOM + R - H Wetting of th e paper is an important for techn olog i 3 cal processes as it helps to separate the ink particles from th e fibers in th e pulper1. Sodium hyd rox ide acts as a To get riel from th e solubl e metal sulphite and ac swelling agent, i.e., favours detac hment of th e dye par etate, filterin g and washing the pulp by wa ter proberl y. ti cles from the fibers and may also cause saponificati on 0.5 per cent of oxa li c ac id (its amount depends on th e of the oil particles, which are present in the ink. But dry weight of pulp( used with sulphuric or aceti c ac id sodium silicate has detergent properti es th at disperse the to reduce th e metal from hi gher va lency to th e lower ink and emul sify the ink vehi cle. Al so, sodium silicate va lency 14 and thi s may faci late the decomposition of acts as a wetting agent which ass ists in the penetration orga nometalli c compounds. of the deinking chemicals to the surface of th e fiber, ag glomeration of ink parti cles, and preventi on of ink re deposition 12. E.ffect of Different Oxidant Acids on Recycled Coloured Role of Oxidant Acid Newsprint
The coloured pigment of th e coloured newsprint are Tabl e 2 shows th at th e bri ghtness of th e produ ced composed of organometallic compound ', thi s pi gment paper treated with aceti c acid is hi gher than the br ight is decolourized by usin g an ox id ant acid in certain con ness of the paper treated with sulphuric ac id by 2.5 per dition in order to reduce th e organometalli c compound . cent , but th e paper produced by treatin g with sulphu ric It is prefered the ac id which has parti al ioni zati on since acid, achi eved the des ired standard specifi cati ons. Treat in this case the H+ protons which is th e essenti al for re ment with sulphuric acid is preferred. sin ce it s pri ce 0 + . cheaper compared with acetic ac id and is ava il ab le in duction did not change to H3 The reacti on beha ves ~1 ., ~ hown hP- low. ln the case of sulohuric ac id " : abundance in Egypt. 652 J SCIIND RES VOL 60 AUGUST 2001
Tab le 3-Eilect of co nce ntrati on of sulphuric ac id on bri ghtness Tabl e 4- Eilec t of tempera ture on bri gh tness and colour and co lour of th e bleaching dein ked coloured newsprint of the bleaching deinked co lou red n ~wsp ri nt
Experiment Brightn ess Co lour Experiment Brightness Co lour
Treated pulp at 70° C 57. 1 white Trea ted pulp with I 0 per cent Treat ed pu lp at 60°C 57 whi te sulphuric ac id 58 . 1 Wh ite Trea ted pu lp at 50° C 57 . 1 tendency to [!rey Trea ted pulp with 5 per cent sulphuric ac id 57 .3 White Time of trea tment 30 min, co nce of H ~ S04 • 3 per ce nt (ha sed on dry we ight of pulp)
Treated pulp with 3 per cent sulphuric ac id 57 . 1 Wh ite Tab le 5-Eilec t of Time During Trea tment With Sulphuric Acid On Brightness And Colour Bleachi ng Deinkcd Treated pulp with 2 per cent Coloured Newsprint sulphuric ac id 50.3 White Experiment Bright ness Co lour Time of treatment: 30 min at 70 "C
Trea ted pulp for 15 min 46.5 Tendency to Effect of Different Concentration of Sulphuric Acid on be grey Recycled Coloured Newsprint Trea ted pulp for 30 min 57.1 whi te From Table 3, we find that the treatment of the old Trea ted pu lp for 45 min 57.3 white coloured newsprint with I 0, 5, and 3 per cent sulphuric acid (based on dry weigh of pulp) gave approx imately Temperatu re 70oC. co ne of sulphuric ac id. 3 rer cent (hased on dry th e same brightness (58 .1 , 57.3 and 57 .1 , respecti vely) , weight or pulp) but treatment with 2per cent sulphuric acid was in suffi mum conditi ons were 3 per cent concentrated sulphuric cient to disintegrate the coloured materials from th e old acid (based on dry weigh of pu lp) at 60°C for 30 min. coloured newsprint, so th e colour of th e produced paper was white havin g tendency to become grey. Role of Hydrogen Peroxide Effect of Temperature and Tim e Variables on Recycled Treating the recycl ed coloured newsprint with 3 per Colored Newsprint During Treatm ent ll'ith Sulphuric cent hydrogen peroxide is necessary for in creasing th e Acid brightness of th e coloured newsprint sin ce the bright It is evide nt from Table 4 th at the brightness at 70 and ness of the waste coloured newsprint decreases during 60°C respectively, was nearly th e same (57. 1 and 57 storage and by the deinking process. Also, hydrogen respectively). But 50°C was not enough to complete the peroxide helps in re movin g the trace of ink present in reacti on ,due to its tendency to become grey. the pulp.
Table 5 shows that th e brightness by treatin g for 45 Ham/sheets jiwn Recvc!ed Coloured Ne wsprint in the or 30 min was nearl y the same ( 57.3 and 57 .I, respec Absence and Presence of'Additives ti vely) , but when the time for treatin g was reached 15 At optimum condition, handsheets were prepared from min , the brightness was found to be 46.5 and the colour recycled coloured newsprint hav in g 48 g/m2 weight. The of the produced paper had tendency to become grey. T hi s physical, mechani cal, and optical prope rti es were mea was attributed to treatment of old coloured newsprint sured before and after the additiv e .~ . The results are li sted for 15 min was for complete the removal of coloured in Table 6, which show that the brightness in creases by materi als from old coloured newsprint. addition of 20 per cent wood pu lp or 20 per cent paper It is concluded from Tables 3, 4 and 5 that for treating sha vings, since the brightness for each ofrhem was hi gher the old coloured newsprint with sulphuric acid the opti - th an the brightness of recycled coloured newsprint but EL-MELIGY & IBRAHIM : DE INK I G & REUSE OF OLD COLOURED NEWS PRJ T
the brightness remains constant by additi on 5 per cent Table 6--Some element present in old coloured newsprint polyvinyl alcoho l. The opacity increases in experiments (a nalysis by spectrophotometer model 2380 Perkin - Elmer Co.) 2, 3 and 4 due to the addition of talc powder as filler
Metal ppm which fills the space between the fibers and this lead to the formation of fiber to fill er bonding and talc make the Fe 37 paper more hydrophobic. Also the sizeability increased Cu 8.2 and this is attributed to th e formation of aluminum re Mn 73 sin ate (rosin size + I 0 per cent aluminum sul phate at Zn 8 pH 4.5) which precipitated on the fiber and thi s leads to Ni 2 the reduction of absorpti vity and prevents spreading of Bl ank (Blended deinked newsprint) ink or colour. The mechani cal properties increased due
Table 7-Physical, optical and mechanical properties of recycled paper from deinked co lour newsprint with or without additives of basic weight 48g/m2
Sample Density, Optical properties Mechanical properties Humid Si zeabili Shade g/cm3 Brightn ess, Opacity, Tens il e Tear it y, ty , s per ceht per cent strength resistance Per kg 0 cent "' Blank (deinked 0.25 57 92. 1 0.8 20 9.5 12 Scan newsprint) blue Deinked news print 57 93 .6 1.5 30 9.5 15 and 5 per cent poly 0.25 vinyl alc ohol Scan blue Blended sample* 0 .3 0 62 .1 92.4 2 36 9.5 17 Scan blue B !ended sample** 0.30 66.2 92.8 1. 86 32 9.5 20 Scan blue * (80 per cent deinked newsprint+ 20 per cent wood Pulp). ** (80 per cent deinked newsprin t + 20 per cen t paper shavings wi th bri ghtness 88 per cent) Bl ank : recycled newsprint without additives. Experi ment 2.3 and 4 were carried out with the addi ti on of 3 per cent talc powder+ 2 per cen t rosin size+ I 0 per cent alum till pH= 4.5 .
Table &-Physical , optical and mechanical propettics of the recycled paper from bleaching deinked blended or (coloured and uncoloured newsprint I: I with or without additives with basic weight 48 g/m2
D::nsity Optical prOJX:It ies Mechanical prope1ties Hunidity, Si zeability, Shade Sample g/crn' Brightness, Opacity. Tensile Tear JX:r pa·cent per cent strength resistaoce cent kg g Blank ( Blended deinked 0.25 56 93 0.81 20 9.5 12 Sc BI ended of dei nked 0.28 56 94 1.6 31 9.5 15 Scan news JYint + 5 per cent poly blue vinyl alcohol Blank : Recycled newsprint without additives. 654 J SC IIND RES VOL 60 AUGUST 2001 to the addition of virgin fibers such as wood pulp or pa 2 Terry Scarlett & elson R Eldred. What the printer should kno11· per shav in gs or due to the addition of 5 per cent polyv i about the ink. (Graphi c A11s Techni..:a l Fou ndati on. 4615 Forhcs Avenu e, Pittsburgh, Pennsyl vania 1523.U SA.) 19X4. lJ2 . nyl alcohol which form additional hydrogen bonds and 3 Orther H, Witek W & FisherS, l?ecrcl Techno!. 21 (20) ( I