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ÖZET Bu tez çalışmasında, %1DD pamuklu kumaşlara reaktif boyarmaddeler ile yapılan baskı işlemini açıklayabilmek için; baskı işlemlerinde kullanılan kimyasal maddeler, bu maddelerin özellikleri, baskı işlemini etkileyen faktörler, baskı için kullanılan makineler, baskı reçeteleri ve baskı işlemleri ile ilgili bilgiler yer almıştır. Reaktif boyarmaddeler parlak, canlı ve oldukça has renkleri ile tanınırlar. Günümüzde bu boyarmaddeler basmacılıkta ve özellikle film basmacılığında en çok kullanılan boyarmaddelerdendir. İşletmede baskı işlemi rotasyon baskı makineleri ile gerçekleşmektedir. Yapılan incelemelerde baskı işleminin verimli olması için dikkat edilmesi gereken hususların başında şablon hazırlama işlemi gelir. Ayrıca baskı patı hazırlanırken hidroliz olayına da dikkat etmek gerekir* Basılacak kumaşların merserizasyon işleminden geçirilmesi baskının verimi açısından tavsiye edilir. İşletmede örgü kumaşlar ağırlıklı olarak basılmaktadır. Reaktif boyarmaddelerin dışında pigment boyarmaddeleri de kullanılmaktadır. Pigmetlerin kullanımında ki ana gaye üretim hızının yüksek olması ve maliyetin düşük olmasıdır. Ancak kumaş tutumu, sürtme haslığı ve yıkama haslığı gibi özelliklerin önem taşıdığı durumlarda reaktif boyarmaddelerin kullanılması kaçınılmazdır. -vii- THE PRINTING DF CDTTDN FABRICS WITH REACTIVE DYES SUMMARY In this research, printing process of cotton fabrics with reactive dyes and machinery are analysed. Printing of textiles may be considered a variation of the dyeing process, where the dyestuff or dyestuffs are applied locally in patterns instead of being disturbed uniformly over the whole surface of the yarn or goods, as in dyeing. But the chemical procedures used for printing differ greatly from the dyeing process. It is important to detect fabric properties and the type of dyestuffs to be applied. The table below can be referred to as a reference listing the possible fabricT dyestuff applications (Table-1). Printing pastes are always prepared with thickeners; for this purpose a number of natural and synthetic products are used. The prime function of a thickening agent in textile printing is to enable the dyestuff or pigment to be transferred to the fabric at the printing stage. Immediately following printing the thickening must contain the dye within the printed area during drying. Furthermore, the thickening agent must not break down during steaming or any other fixation process to such an extent that colour `bleeding`occurs. Finally9 the thickening agent must be completely removed from the fabric during the washing-off treatment given to the dyestuffs. One for their requirement is that the thickening agent must be compatible with all other components in the print paste, and it must not be too expensive. The classification of natural thickeners used in textile printing is shown on Table-2. The weight of dry thickening agent required to prepare the print paste of correct viscosity varies from product to product. This depends essentially on the chain length and degree of chain branching in the thickening agent molecules. Where relatively large -Vlll-TABLE 1. Applicability of Various Dyestuff Classes to Different Fibres In Textile Printing. Sİ B Suitable and of in ft Kil SLF * Suiublc tul laıiı f-n.ı.tu Silo. Suİublt bul Uci» iiıtmu and it now obwIcHreal SUD » Suitable bul uuge declining SO *? SuHitlc bul ubkoitn-cı.i HS ` Nol tuıUblc NSt * No l suıUblc cxicpl in d bit blende TABLE 2. Natural Gums Used In Textile Prinbing. Extraction Source Gum Name Trade Name Trees and shrubs Plant or tree seeds Seaweed Gum Arabic, Gum Senegal Gum Tragacanth and Gum Karaya Locust Bean gum Guargum and starches Sodium alginate Carragheenan Gum Gatto and Cesal- piniagum (Cesalpina, Italy) Manutex (Alginate Inds.) and Lamitex (Pro tan, Norway) Irish Moss (Blandola, UK) -IX-weights of dry thickener are required, as B % and more, the resulting thickening isdescribed as being of medium or high solid content. Conversely thickenings made with less dry agent are of low solids content. Thickening agents must possess satisfactory mechanical properties under printing conditions, otherwise an even print will not result. The relationships between high and low solid thickeners are summarized in the table below (Table-3). TABLE 3. The Interrelationship Between Low And High Solid Thickening Properties. Besides the thickening agent the binder used in pigment printing are also an important parameter in order to establish the right printing process. As it is known that the function of binders is to adhere the dyestuffs to the surface of fibre consequently to fabrir. The type and the concentrations of the binders have to be chosen according to the level of the dyestuffs applied as well as the crocking and washing fastness. -x-In order to get better printing properties the other auxiliaries such as softeners, disperants, smülsif iers, wetting agent, calatysts and fixators are also important parameters. Printing machines can generally he classified as screen, block, and roller. The most selected parameter in order to use the printing process is its high production. Dur samples are printed by rotary screen machines. For every colour different screens are prepared. In its simplest terms a printing process involves the following stages: 1- Preparation of print paste 2- Printing of fabric 3- Drying k- Fixation of dyestuff 5- üJashing-off When printing on cotton, the maximum yields are obtained from a mercerized fabric. It is essential that the final preparation treatments given to the cellulose substrate leave the fabric in a neutral or slightly alkaline condition. Any acidic reaction of the fabric or the presence of residual starch on the fabric will give rise to a lowering in the colour yield from reactive dyes. When selecting reactive dyes for printing, the factors of importance for dyeing must be considered but, in addition, attention must be paid to print-paste stability and staining of the ground during washing-off. Alginates are the only natural thickeners found to be suitable for printing with reactive dyes. All other carbohydrates react with the dye and this results in low colour yields or unsatisfactory fabric handle due to insolubilization of the thickener. Alkali is essential to produce ionization of accessible cellulose hydroxyl groups which can then react with reactive dye. Sodium bicarbonate has been the preferred alkali because it is cheap and gives high print-paste stability with all but the most reactive dyes. Uhen the stability of the dye is high enough -xi-sodium carbonate may be preferred because the dyes of higher stabiliiity ' will give higher colour yields under more alkaline conditions. During our research at the plant, it is seen that one of the most possible source of printing faults is the unsuitable screens. The causes of printing faults originated from screens can be summarized as follows: a) Frothing of the sensiting solution b) The sensiting solution applied unevenly c) Very humid atmospheric conditions during application of the sensiting solution d) Temperature too high during exposure e) Screens kept too long at a high temperature before exposure f) The screen has not been in perfect contact with the positive g) Impurities or grease on the screen before coating. -Xll- 62 |
