Changhai Xu

Establishment of an activated peroxide system for low-temperature cotton bleaching using N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride

Cotton bleaching is traditionally carried out in strongly alkaline solution of hydrogen peroxide (H2O2) at temperatures close to the boil. Such harsh processing conditions can result in extensive water and energy consumptions as well as severe chemical damage to textiles. In this study, an activated peroxide system was established for low-temperature cotton bleaching by incorporating a bleach activator, namely N-[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) into an aqueous H2O2 solution. Experimental results showed that the TBBC-activated peroxide system exhibited the most effective bleaching performance in a pH range of 6-8 which could be approximated by adding sodium bicarbonate (NaHCO3). The TBBC/H2O2/NaHCO3 system led to rapid bleaching of cotton at a temperature as low as 50°C. In comparison with the hot alkaline peroxide bleaching system, the TBBC/H2O2/NaHCO3 system provided cotton fabric with an equivalent degree of whiteness, higher degree of polymerization, and slightly lower water absorbency. The new activated peroxide system may provide a more environmentally benign approach to cotton bleaching.

Analysis of factors affecting the performance of activated peroxide systems on bleaching of cotton fabric

Abstract A screening experiment was designed to investigate the possible factors affecting the performance of activated peroxide systems (APSs) on bleaching of cotton fabric. The design of experiment comprised thirteen factors such as type of bleach activator (BA), concentration of bleach activator ([BA]), molar ratio of hydrogen peroxide to bleach activator ([H2O2]:[BA]), type of peroxide stabilizer (PS), concentration of peroxide stabilizer ([PS]), type of wetting agent (WA), concentration of wetting agent ([WA]), pH value of bleach bath (pH), bleaching temperature (T), bleaching time (t), liquor-to-goods ratio, cotton substrate (C), and water quality (W). The bleaching performance of APSs was accessed by measuring the degree of whiteness of bleached cotton fabric which was defined as the response factor for statistical analysis. The screening analysis revealed that C was the most significant factor affecting the performance of APSs on bleaching of cotton fabric, followed by T, BA, [BA], pH, PS, and [H2O2]:[BA]. Additionally, two-factor interactions were found as well between C and T, T and pH, C and BA, C and [BA], T and [BA], W and [PS], C and PS, and pH and [H2O2]:[BA]. These significant main effects and two-factor interactions were interpreted in details for a better understanding of the performance of APSs on bleaching of cotton fabric. The findings of this study are valuable for further establishment and optimization of APSs for low-temperature bleaching of cotton fabric.

Performance modelling of the TBCC-activated peroxide system for low-temperature bleaching of cotton using response surface methodology

Abstract In this study, an activated peroxide system was established for low-temperature bleaching of cotton by incorporating N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC), hydrogen peroxide (H2O2) and sodium bicarbonate (NaHCO3) into an aqueous solution. The bleaching performance was modelled by response surface methodology based on a central composite rotatable design of experiment, in which concentration of TBCC ([TBCC]), concentration of NaHCO3 ([NaHCO3]), temperature (T) and time (t) were four independent variables, and the degree of whiteness (DoW) of bleached cotton was measured as the response variable. For each individual bleaching experiment, TBCC and H2O2 were used in a molar ratio of 1:1.1 and NaHCO3 in a molar amount greater than that of H2O2 for the purpose of driving reactions to completion. A reduced quadratic model (RQM) was constructed using regression analysis with backward elimination, which was used to conduct a practical low-temperature bleaching process for cotton. In comparison to the typical conventional peroxide system, the TBCC-activated peroxide system based on the RQM predication provided cotton with an equivalent DoW and slightly inferior water absorbency, resulted in no apparent damage to cotton fibers, but worked under much milder conditions. This study provides useful insights into scaling up the TBCC-activated peroxide system for low-temperature bleaching of cotton.

Regenerated cellulose fibers spun-dyed with carbon black/latex composite dispersion

A carbon black (CB)/latex composite was prepared by the method of miniemulsion polymerization for use as a colorant for spun dyeing of regenerated cellulose fibers. Analysis of experimental results revealed that the CB/latex composite had a small particle size and a narrow particle size distribution which were important to ensure a stable dispersion being later added to spinning solution. A good stability of the prepared CB/latex composite dispersion in the spinning solution indicated that it was highly possible to use the CB/latex composite as a colorant for spun dyeing of regenerated cellulose fibers. When a 3.5% mass ratio of CB/latex composite to cellulose was used for spun dyeing, the spun-dyed fibers had the highest tensile strength, breaking elongation and color strength. The rubbing and washing color fastnesses of spun-dyed regenerated cellulose fibers could satisfy requirements of most textiles. This study provided a new insight into producing spun-dyed regenerated cellulose with a novel colorant.

Recognizing a limitation of the TBLC-activated peroxide system on low-temperature cotton bleaching

In this study, cotton was bleached at low temperatures with an activated peroxide system which was established by incorporating a bleach activator, namely, N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) into an aqueous solution of hydrogen peroxide (H2O2). Experimental results showed that the bleaching performance was unexpectedly diminished as the TBCC concentration was increased over the range of 25-100g/L. Kinetic adsorption experiment indicated that this was most likely ascribed to the adsorptive interactions of TBCC and the in situ-generated compounds with cotton fibers. Such a limitation was especially fatal to cold pad-batch bleaching process of cotton in which a high TBCC concentration was often required. The results of this study may stimulate further research to avoid or overcome the limitation of the TBCC-activated peroxide system on low-temperature cotton bleaching.

Preparation of SiO2/PSSS dispersion for formulation of white inkjet ink

SiO2 particles were prepared by sol–gel method and further modified with γ-methacryloxypropyltrimethoxysilane (KH570). A SiO2/PSSS composite was prepared with a core–shell structure, by the in situ polymerization of p-styrene sulfonate sodium (SSS) and the reaction with the KH570-modified SiO2. The SiO2/PSSS composite was optimized by adjusting the mass ratios of KH570 to SiO2, SSS to SiO2 and APS to SSS for control of the particle size and polymer layer thickness. Fourier transform infrared spectrum, contact angle and thermogravimetric analysis indicated that PSSS was successfully coated onto SiO2 particle surface. Transmission electron microscopy images showed that the prepared SiO2/PSSS dispersion had small particles and narrow particle size distribution. The white inkjet ink prepared from the SiO2/PSSS dispersion exhibited excellent thermal and centrifugal stabilities. The white inkjet ink was applied for pretreatment of fabric before colored printing which resulted in a significant enhancement of pattern brightness.

X-ray photoelectron spectroscopy analysis of cotton treated with the TBCC/H2O2/NaHCO3 system

N-[4-(triethylammoniomethyl)benzoyl]caprolactam chloride (TBCC) was used as a bleach activator for activation of hydrogen peroxide (H2O2) in aqueous solution with the addition of sodium carbonate (NaHCO3). The TBCC/H2O2/NaHCO3 system was applied for treatment of cotton greige fabric at 60℃ in comparison with the conventional H2O2/NaOH system for treatment of cotton greige fabric at 95℃. Experimental results showed that the TBCC/H2O2/NaHCO3 system was effective for improving the degree of whiteness, reducing the fiber damage, and improving the water absorbency of cotton fabric. For understanding the treatment performance of the TBCC/H2O2/NaHCO3 system, X-ray photoelectron spectroscopy (XPS) was applied to analyze the surface elemental composition of cotton greige fabric before and after treatment. C 1s XPS spectra and quantitative analysis revealed that the TBCC/H2O2/NaHCO3 system improved the water absorbency of cotton fabric by removing hydrophobic matters as well as by oxidizing coloring matters and cellulose. The hexane extractions and scanning electron microscopy images indicated that the TBCC/H2O2/NaHCO3 system most likely removed the hydrophobic matters from cotton fabric in a “layer-by-layer” mode, which limited the cellulose backbones exposed for XPS analysis but allowed water to penetrate into cotton fibers.

Pilot-plant investigation on low-temperature bleaching of cotton fabric with TBCC-activated peroxide system

Cotton fabric was bleached at a pilot-plant scale with the activated peroxide system based on N-[4-(triethylammoniomethyl) benzoyl] caprolactam chloride (TBCC). The performance of the TBCC-activated peroxide system on low-temperature bleaching of cotton fabric was evaluated by measuring the degree of whiteness, degree of polymerization, water absorbency, extractable contents, and dyeing properties of bleached cotton fabrics. For comparison purpose, cotton fabric was also bleached at the same pilot-plant scale with a traditional hydrogen peroxide system using a standard recipe. It was found that the pilot-plant bleaching with the TBCC-activated peroxide system resulted in a comparable degree of whiteness and a slightly lower water absorbency of cotton fabric but no apparent fiber damage. The bleached cotton fabric could meet requirements for trichromatic reactive dyeing. The investigation on resource utilization revealed that the pilot-plant bleaching of cotton fabric with the TBCC-activated peroxide system could save 60% water, 38% steam and 27% electric power in comparison with the traditional hydrogen peroxide system. These pilot-plant results are of great importance for further scaling up the TBCC-activated peroxide system to full-scale commercial production.

A nonlinear isotherm model for sorption of anionic dyes on cellulose fibers: a case study.

The sorption data of an anionic dye on cellulose fiber are often correlated with a log-linear model to determine the internal accessible volume of the fiber to the anionic dye (V, L/kg) and as such the standard affinity of the anionic dye to the fiber (-Δμ°, J/mol), but without taking into account the influence of ionized carboxyl groups due to cellulose oxidation ([COO(-)]f, mol/kg). In this study, a nonlinear isotherm model was derived by incorporating [COO(-)]f, V and -Δμ° as three model parameters. A set of classical sorption data of C. I. Direct Blue 1 on bleached cotton was correlated with the nonlinear isotherm model. The nonlinear curve fitting analysis showed that the nonlinear isotherm model was in excellent agreement with the sorption data and robust to determine the values of [COO(-)]f, V and -Δμ° for describing the sorption behaviors of anionic dyes on cellulose fibers.