Ofset Baskıda Yüzey Düzgünlüğünün Geri Dönüşümlü Kâğıtlardaki Tram Ton Değerlerine Etkisi
Öz
Normal bir kağıt hamuru hazırlanması aşamasında, birincil lifler kullanılır ve bu lifler uzun ve kısa liflerden oluşmaktadır. Geri dönüşümlü kağıtların üretim aşamasında, kağıt hamuru hazırlanırken hem birincil lifler hem de ikincil lifler kullanılmaktadır. İkincil lifler daha önceden kullanılmış, pre- consumer (tüketim öncesi) ve post-consumer (tüketim sonrası) olarak adlandırılan liflerdir. Yalnız bu lifler daha önce işlem gördüğü için, birincil lifler kadar formal değildir. Bu çalışmada; birinci hamur ve farklı lif yapılarına sahip olan çeşitli geri dönüşümlü kağıtlar üzerine, birinci hamur baskılarda en çok kullanılan çıkış çözünürlükleri olan 133lpi ve 175 lpi değerleri ve %20, %50 ve %70’lik tram ton değerleri mevcut olan baskı kontrol şeridi kullanılmıştır. Basılan tram ton yoğunlukları elektron mikroskobu ile büyültülerek, tram ton değerlerinin her iki baskı çözünürlüğündeki sonuçlarında, görsel olarak farklılıklar tespit edilmiştir. Geri dönüşümlü kağıtlar üzerine yapılan baskıda yüzey pürüzlülüğünün tram ton değerlerine ve mürekkep dağılımına etkisi incelenerek uygulayıcıların hizmetine sunulmuştur.
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The Effects of the Surface Roughness on the Dot Area of Recycled Papers in Offset Printing
Öz
In the production of normally paper pulp, primary fibers are used. This fibres are consist of both long fibres and shortfibres. In recycled paper production however, both primary fibres (short and long fibres) and secondary fibres are used.Secondary fibres divide into pre-consumer and post-consumer fibres. However these fibers are not as formal as primary fibersbecause of the re-processing.In this study, the differences in the dot area in offset printing applied to 1st.Pulp and various recycled papers that havediffering fibre structures have been identified. With this intention, 133 lpi and 175 lpi output resolutions are widely used for1st.Pulp and dot gains of 20%, 50% and 70% in test materials have been obtained. With the aim of examining the effect of dotarea in printing on recycled papers, enlarged images taken from the scanning electron microscope (SEM) were used. As a result,how does the dot area effect of the differences between the fibre structure and surface roughness of recycled papers, aredetermined in this study.Keywords: Recycled paper, surface roughness, dot area, deinking, bleaching1. INTRODUCTIONWith a daily calculation of 5 million tons, eachyear Europe produces approximately 2 billion tons ofused solid waste. Between the years 1970-1980 theincrease in the demand for recycled fibres was twotimes that of what was obtained from cellulose. Todayhowever, the demand for recycled fibres in WesternEurope is increasing four times faster than the demandfor fibres obtained from raw cellulose. Towards the endof 2001, the proportion of paper thrown away wasaround 98%. The amount of paper wasted in EasternEurope is 80% while it is expected to rise at a rate of41% for the whole world (1).In recent years recycling has increased. TheEuropean Waste Commission is preparing a formalsurfaces have higher gloss. Correlations between paperroughness and paper and gloss were studied also by Xuet. All (8)Using cellulose obtained from low intensity anddifferent tree materials, volume and opaqueness can beincreased. In proportion to similar used papers, surfaceroughness and absorption are found to be greater whilegloss and the binding strength of fibres have been foundto be low. These characteristics depend on the source ofthe fibre, recycling processes and on the productobtained (9).Although the production stages of recycledpapers are similar to that of papers produced directlyfrom cellulose, they are different in terms of fibrestructure, deinking and flatosyon chemical stages. As aresult, fibre structure and surface roughness also show adifference (10).In this study; by enlarging the dot area in offsetprinting of papers produced by recycling waste papersusing an scanning electron microscope, the differencebetween the dot area of various types of paper isidentified.2. MATERIAL AND METHOD2.1. Papers Used In The StudyIn this study, the printable parameters of recycledpapers have been realised after being printed withparameters that were developed for 1st. Pulp paper.With this intention, papers that have good/bad surfaceroughness, that are white/non-white and that have/havenot had deinking applied to it, have been chosen fromtwo companies that sell recycled paper in Turkey.The first three recycled papers used in theexperimental studies, are recycled papers, (P1,P2,P3)that have been produced from 50% waste paper ofwhich 20% of this is classified as post-consumer waste.One of the last two recycled paper (P4), is madefrom 65% pre-consumer waste, 10% post-consumerwaste and 25% raw cellulose fibres.The other of the last two recycled paper (P5), ismade from 75% recycled waste paper according toNAPM (National Association of Paper Merchants)valuations and 50% when equalized according toEurope EUGROPA values. Consequently, the amountof pre-used and post-used waste has been confused witha value that has not exactly been identified.Characteristics of papers used in the study:- 1st. Pulp, 110 g/m2,- UNIREP, Rhododendron Soft White, 110g/m2, (named P1)- UNIREP, Elements Soft White Solid, 110g/m2 , (named P2)- UNIREP, Elements Soft White Grain, 110g/m2 , (named P3)- TIMAS, Conqueror Recycled Barley WhiteLaid, 100 g/m2, (named P4)
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