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<J.7 Whit e Hemicellul ose, per ce nt 18.5 15 .4 Pulp treatedwith IOpercent Lignin , per cent 20.1 18 aceti c acid 60.5 Wh ite 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.