LEE- Tekstil Mühendisliği Lisansüstü Programı

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http://hdl.handle.net/11527/19465

Gözat

Yazar "Altay, Pelin" ile LEE- Tekstil Mühendisliği Lisansüstü Programı'a göz atma
  • Öge
    Synthesis of bleach activators for textile industry
    (Graduate School, 2021-06-29) Altay, Pelin ; Gürsoy, Nevin Çiğdem ; 503132801 ; Textile Engineering
    Cotton fiber, is the most widely used natural fiber worldwide, contains undesired natural yellowish-brown coloring matters that hinder absorbency (wetting), reduce the natural whiteness of the fibers. These coloring impurities, which may cause poor dyeing quality, poor finishing performance and end product defects, must be removed by bleaching process to prepare the textile materials for dyeing and finishing. Hydrogen peroxide (H2O2), a universal and environment-friendly bleaching agent, is widely used for cotton and cotton blends. Conventional hot hydrogen peroxide bleaching is conducted under alkaline medium (pH 10.5–12) at high temperatures near boiling (at around 98 °C), leading extensive use of energy and severe chemical damage to textiles. Increasing demands for textile bleaching include reduction in processing costs (energy and water consumption), reduction in environmental impact and improvement in quality. Since energy is one of the main cost factors in textile industry, there has been considerable interest in recent years in ''low temperature'' bleaching. Activated peroxide systems have been investigated as an alternative approach to cotton bleaching at lower temperatures. Although there have been many reports on the use of cationic bleach activators for cotton bleaching, yet it has never reached the commercial success due to either production cost on a large scale, environmental concerns and/ or activity. This study focuses on the development and synthesis of novel, sustainable based on aliphatic acid chloride and more cost-effective cationic bleach activators, with the aim of reduced production cost, improved affinity and bleaching performance, reduced fiber damage for low temperature cotton bleaching to overcome the drawbacks of conventional hot hydrogen peroxide bleaching and other cationic bleach activators based on aromatic acid chloride. Compared to conventional peroxide bleaching, using a bleach activator in a peroxide bleaching bath is an effective and kinetically more potent oxidation generating highly reactive peracid in situ, providing low-temperature bleaching. Activated bleach systems have the potential to produce more efficient kinetically potent bleaching systems through increased oxidation rates with reducing energy cost, saving time and, hence, causing less cellulose polymer chains damage or degradation than conventional hot peroxide bleaching. Cationic bleach activators have been investigated as the next generation bleach activators with inherent substantivity towards cellulosic fibers. In this study, facile synthesis of more sustainable and cost-effective bleach activators (N-[4-(N,N,N)-triethylammoniumchloride- butyryl] caprolactam, TBUCC, and N-[4- (N,N,N)-triethylammoniumchloride- butanoyl] butyrolactam, TBUCB, based on an aliphatic acyl chloride (4- chlorobutyryl chloride), was reported. Fourier transform infrared and high resolution mass spectrometry and 1HNMR confirmed the molecular structure of the synthesized bleach activator. Bleaching performance of newly- synthesized bleached activators was evaluated in terms of whiteness index, water absorbency and fiber damage (degree of polymerization) and compared with conventional peroxide system. Central composite design (CCD) (orthogonal blocks) was used to establish an optimized TBUCB-activated hot peroxide-cotton bleaching system at lower temperature for providing reduced energy cost and maintaining the integrity of cellulose polymer chains. The significance of the process parameters (independent variables) and their interactions were statistically evaluated using Minitab. First principles density functional theory (DFT) calculations were performed to elucidate the reaction mechanism via identifying plausible transition state(s) of the nucleophilic attack of perhydroxyl anion (HOO-) with different carbonyl carbons and identifying the advantages and limitations of TBUCB activator for hydrogen peroxide bleaching for cotton. The synthesis of bleach activators was conducted using a two-step reaction procedure. In the first step, intermediate product was synthesized by condensation reaction of 4- chlorobutyryl chloride with lactam leaving groups (caprolactam and butyrolactam). In the second step, quaternization step was performed to obtain the cationic bleach activators. Experimental results show that, in TBUCC-H2O2 system, the whiteness index (WI) of bleached samples improved when 1:8 and 1:10 molar ratio of TBUCC: H2O2 was used at 60 °C for 30 min. Using 1:8 molar ratio of TBUCC: H2O2 at 36.7 mmol/L activator provided a WI of 70. As the temperature increased from 60 to 70 °C, WI increased to 75.72 and 78.97 at 1:10 and 1:12 molar ratio of TBUCC to H2O2, respectively. The optimum pH was found to be 11.5 for effective bleaching performance. It was concluded that the effective concentration of generated PAA depends on the concentration of H2O2 up to a certain level. Based on the results of the experimental design and statistical analysis, a WI higher than 70 was achieved for TBUCB-activated bleach system at 9.47 g /L (29.7 mmol/L) and higher activator concentrations and at a molar ratio of 1:6-1:10 activator: H2O2. WI higher than 80 can be achieved between 11.7 g/L (36.7 mmol/L) and 13.93 g/L (43.7 mmol/L) of activator concentrations at a temperature of 80 0C. Considering the significance of the process parameters (independent variables) and their interactions, temperature (D) followed by molar ratio of activator: H2O2 (B) and concentration of activator (A), respectively, have the highest statistical relevance on whiteness index. On the other hand, it was revealed that the two-way interaction between the concentration of activator (A) and the molar ratio of activator: H2O2 (B) is greater than the other two-way interactions. When the bleached samples with similar whiteness values were compared (WI= ~ 75) in terms of fiber damage for conventional and activated peroxide bleaching systems, a 19.5% decrease in the average degree of polymerization (DP) was observed in conventional peroxide bleaching, while a decrease of 11.4% and 9.8% was observed in the TBUCC and TBUCB activated peroxide bleach systems, respectively. All these results show that whiteness index greater than 80 for cotton can be achieved by using TBUCC and TBUCB activated peroxide bleaching systems at lower temperature, providing reduced energy cost while maintaining the integrity of cellulose polymer chains. Density functional theory calculations were performed to elucidate the reaction mechanism of the bleach activator with cellulose and rationalize the superior efficiency of the bleach activator while maintaining the integrity of cellulose polymer chains compared to conventional hydrogen peroxide bleaching. DFT calculations elucidated the reaction mechanism, reactivity and peroxide bleaching reaction pathway of the perhydroxyl anion attack at carbonyl group of the butanoyl segment not at the carbonyl carbon of the butyrolactam, which is consistent with the experimental results. Reactions were found to follow two step mechanisms, which are perhydroxyl anion attack at the carbonyl carbon and the peracid formation. Reaction barrier for the perhydroxyl anion attack at the carbonyl carbon was calculated by using sum of electronic and thermal free energies at 70 ̊C under water solvation effect and determined as 12.55 kcal/mol. For perhydroxyl anion attack, TBUCB was found to have a lower reaction barrier and higher solubility than TAED, which was determined as 13.72 kcal/mol. These newly developed and synthesized aliphatic acid chloride-based cationic bleach activators, which are more cost-effective, sustainable and highly reactive compared to other aromatic based cationic bleach activators, enable peroxide bleaching possible at lower temperature (70 0C) compared to conventional hot peroxide bleaching (98 0C). With a sustainable production approach, using these novel cationic bleach activators in hot peroxide bleaching bath provides many advantages such as energy savings, reduced production cost, improved affinity and bleaching efficiency (whiteness index), and less fiber damage. This study provides key fundamental science principles and suggestions at the molecular level of novel and sustainable bleach activators for cotton using a combined experimental and first principles DFT calculations. This study is expected to provide a great contribution to the commercialization of these novel, more sustainable and effective cationic bleach activators for cellulose and cellulosic materials and to the future development of cost-effective industrial bleach activators and sustainable bleaching systems.