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Preparatory Chemical Processes and Recent Developments
Published in Asis Patnaik, Sweta Patnaik, Fibres to Smart Textiles, 2019
Naveen V. Padaki, Brojeswari Das, Subhas V. Naik, Sanganna A. Hipparagi
Apart from natural impurities, added impurities such as starch size are present in cotton fabrics, which have to be removed in preparatory processes. Desizing is the process of removal of added impurities from cotton and cotton-blended fabrics. Starch-based size is often applied to cotton and cotton-blended warp yarns before weaving to avoid yarn breakage, improve yarn strength and also to decrease friction during weaving. This size has to be removed during preparatory process as a first step, before further chemical processing. Although many methods of desizing process exist, textile industries worldwide have adapted to enzymatic desizing process. α‐Amylase is a hydrolytic type of enzyme that catalyzes the breakdown of starch size into short-chain sugars, dextrin and maltose fractions, thereby aiding the removal of size from fabrics. Figure 8.6 illustrates the process chart for desizing using conventional amylase enzymes. Generally, 1% of amylase enzyme on weight of fabric is dosed and treated at 60°C for 1 h in the pH range of 5.5–6.5 for effective desizing (Cavaco-Paulo and Gübitz 2003). Sometimes, apart from starch-based size, synthetic polyacrylate-based sizes may also be present in some cotton fabric lots. Acidic desizing with 0.1N HCl is carried out on those fabrics where enzymatic desizing is not effective. Cotton fabrics after desizing process may lose up to 7%–10% weight due to removal of size.
Enzymes Fundamentals
Published in Sulaiman Al-Zuhair, Hanifa Taher, Supercritical Fluids Technology in Lipase Catalyzed Processes, 2016
Sulaiman Al-Zuhair, Hanifa Taher
In fabric manufacturing, threads are coated prior to weaving with a substance that prevents threads breaking during weaving. Many substances such as starch and polyvinyl alcohol have been used for this purpose. However, these should be removed after weaving. The desizing (size removal) process is usually carried out using chemicals such as acids, alkyls, or oxidizing agents. However, these chemicals are not recommended due to their environmental impact. Starch-breaking enzymes (amylase) are used instead due to their high efficiency in removing size without affecting the fabric and its specific character.
Process optimization for pre-treatment and dyeing one bath of viscose fabric with enzyme in cold pad-batch
Published in The Journal of The Textile Institute, 2018
Yuanzhao Zhu, Weitao Zhou, Pei Xiao, Yanan Zhao, Xinmei Guan, Zhenfang Chang, Zhengping Xia, Qing Wang
In response to the call of international energy conservation and environmental protection, a green production technology is urgently needed. In comparison to conventional exhaust dyeing method, the cold pad-batch (CPB) dyeing method offers the most economical and convenient method of dyeing viscose fiber with reactive dyes (Khatri et al., 2014). It is more eco-friendly and economically feasible process，with lower consumptions of energy and water as well as the emission of salt. (Khatri, Memon, Khatri, & Tanwari, 2011; Siedow, 2000). And the enzyme, a specific biocatalyst can accelerate size decomposition into water soluble simple sugar, offers cleaner, environmentally-friendly and economical method (Ali, Khatri, Khatri, & Tanwari, 2014). Nowadays, enzyme is commercialized and preferred for desizing due to their high efficiency and specificity, completely removing the size without any harmful effects on the fabric (Esfandiari, Firouzipouyaei, & Aghaeimeibodi, 2014).
Truncated α-amylase: an improved candidate for textile processing
Published in Preparative Biochemistry and Biotechnology, 2018
Poulomi Saha, Mohd Faheem Khan, Sanjukta Patra
Moreover, the first step of fabric finishing is desizing that is the most crucial process, since it involves the removal of sizing materials (such as starch, frequently used as sizing materials) applied and coated on the yarn surface to protect the fabrics from harsh chemical and mechanical processing.[7] The advantages of sizing implicates improving the weave ability of warp yarn by making it more resistance to absorption, friction, tensile strength, elasticity, hairiness, etc. to maintain good fabric quality.[8] On the other hand, desizing is an essential chemical process of all textile processing industries. In wet processing, it removes sizing material from fabric before completing the pretreatment process, necessary before dyeing, printing, and polishing. The purpose of desizing of yarn is to improve absorbing capacity and affinity of fabrics toward chemicals in dyeing and printing process.[9] There are various types of desizing methods. The oxidative, acid- and water-soluble desizing methods have various drawbacks such as oxidation processes generates hydroxyl radicals that oxidizes majority complex chemicals in wastewater; mineral acids are harmful to cellulose fibers that causes the formation of hydrocellulose which weaken the fabric; and water-soluble desizing is inefficient to remove all sizing material.[10] In contrast, enzyme desizing is the most widely practiced method of desizing and usually employs amylases for removal of coated starch. The advantages of enzyme desizing are they have eco-friendly characteristics and do not produce any toxic by-products and therefore, they are increasingly required for textile industries to reduce pollution in textile production.[2]
Evolution in the surface modification of textiles: a review
Published in Textile Progress, 2018
Ayoub Nadi, Aicha Boukhriss, Aziz Bentis, Ezzoubeir Jabrane, Said Gmouh
Desizing is the process in which the size that had been applied to the warp yarn before weaving is removed to facilitate the penetration of dyes and chemicals in the subsequent wet-processing operations. Desizing of fabrics can be accomplished by physical, chemical or a combination of physical and chemical mechanisms, through rot steeping, acid steeping, treatment with enzymes and oxidizing agents whereby the insoluble starches and polymers are converted into sugars or simple water soluble polymers in order to ease their removal [5]. The synthetic sizes used for man-made fibres are generally water soluble, so they are removed during the scouring operation.