Bleach activation of thermomechanical pulp

Under mild alkaline condition the bleaching activator tetraacetyl ethylenediamine (TAED) forms peroxyacetic acid with sodium perborate and improves the brightness of thermomechanical pulp. The activator makes it possible to bleach the pulp efficiently even without addition of sodium hydroxide at any temperature in the range 40 to 70°C. A mathematical model has been proposed to allow estimation of the total peroxy acid consumption during activated bleaching process. Using this model it is possible to calculate the extent of peroxy acid decomposition by predetermining the rate constant and activation energy. The effect of bleach activation was found to be maximum at temperatures below 60°C. The influences of bleaching time, pH, consistency, temperature and TAED charge on the bleach activation has been evaluated. The activator is effective enough to improve the brightness of sodium perborate bleached pulp at an average charge of about 50 mass% of sodium perborate. Apparently, high consistency dispersive bleaching without free alkali is a technological and economic advantage of the process.     

Enhanced PAA bleaching of cotton by incorporating a cationic bleach activator

Peracetic acid is a well-known alternative to hydrogen peroxide as a bleaching agent for cotton. In this study, a novel cationic bleach activator, N -[4-(triethylammoniomethyl)benzoyl]butyrolactam chloride, was used in combination with peracetic acid to investigate the enhancement of cotton bleaching efficiency. The effects of temperature, pH and concentrations of activator and peracetic acid on the bleaching performance were studied using a statistical design of experiment. Adding activator to a peracetic acid bleaching bath improved the resultant whiteness of the substrate and at optimal conditions produced less fibre damage than when peracetic acid was used alone. In addition, the bleaching performance of both peracetic acid and hydrogen peroxide in the presence of activator was compared. In the absence of activator, the peracetic acid performance was considerably superior to a conventional hydrogen peroxide bleach system in which no bleach activator is present. However, addition of activator to the hydrogen peroxide bath increased the whiteness to a level comparable to peracetic acid.     

Synthesis of N‐[4‐(dimethylalkylammoniomethyl) benzoyl]caprolactam chlorides as cationic bleach activators for low‐temperature bleaching of cotton fabric under near‐neutral pH conditions

Low‐temperature bleaching of cotton fabric can be achieved by incorporating a so‐called bleach activator into an aqueous solution of hydrogen peroxide. In this study, a series of N‐[4‐(dimethylalkylammoniomethyl)benzoyl]caprolactam chlorides were synthesised for use as cationic bleach activators with various alkyl chain lengths. All these synthesised cationic bleach activators were confirmed by ¹H and ¹³C nuclear magnetic resonance spectroscopy and mass spectroscopy. Bleaching experiments revealed that these synthesised bleach activators were effective for bleaching of cotton fabric at 50 °C under near‐neutral pH conditions, but the alkyl chain lengths had a great influence on their bleaching performance. Increasing the alkyl chain length from 2 to 6 carbon atoms could slightly enhance bleaching performance, while increasing the alkyl chain length from 8 to 16 carbon atoms markedly reduced bleaching performance.     

Stability of a novel cationic bleach activator in aqueous solution

The hydrolytic stability of a novel cationic bleach activator, N -[4-(triethylammoniomethyl)benzoyl]capro-lactam chloride, in aqueous solution has been investigated. After treatment with a bleach system, the whiteness of cotton fabric was measured. Assessment of the available oxygen was used to assess the stability of the bleach activator in solution with respect to time, using a method which minimised the effect of hydrogen peroxide on total available oxygen. Whereas the N -[4-(triethylammoniomethyl)benz-oyl]caprolactam chloride in solid form was found to be stable, in aqueous solution it was relatively easily hydrolysed. The effect of pH on its stability in solution was assessed. A good correlation was found between change in available oxygen on storage and bleaching performance.     

Terpyridine-manganese complexes: A new class of bleach catalysts for detergent applications

Oxidation catalysis is one approach used to improve the performance of hydrogen peroxide in laundry bleach applications. We introduce herein a new class of bleach catalysts based on the ligand 2,2′∶6′,2″ terpyridine. A set of manganese complexes of substituted terpyridines was investigated with respect to their physicochemical properties and bleach performance. Introduction of electron-donating hydroxy and amine substituents in the 4-position of the individual pyridine rings improves the bleach performance in model experiments with morin (2′,3,4′,5,7-pentahydroxyflavone) in solution as well as on tea-stained cotton fabrics. All the catalysts show excellent bleach performance at 40 and 25°C under European washing conditions. Performance is superior to that of the activator tetraacetyl ethylenediamine (TAED) but depends critically on the substitution pattern. Dye damage caused by the catalysts is similar to that of TAED, proving that catalytic bleach systems with high performance and low damage are indeed feasible. Model experiments revealed that the complexes are highly stable under aqueous alkaline conditions in the presence of hydrogen peroxide. The optimal pH for catalytic activity is about 10. For a catalyst to have a high bleach performance, it must possess a sufficiently low activity to catalyze disproportionation of hydrogen peroxide, which is a major side reaction of catalytic bleach with manganese complexes. All the catalysts showed a similar affinity for the cotton fabric, suggesting that differences in bleach activity of complexes are not caused by differences in the fabric affinity.     

Bleaching of cotton with activated peroxide systems

The bleaching performance of a novel cationic bleach activator, N -[4-(triethylammoniomethyl)benzoyl]-caprolactam chloride, was compared to that of nonanoyloxybenzene sulphonate, a commercially available anionic bleach activator. The whiteness of bleached cotton fabric was used as a measure of the performance. Comparison of bleach performance and the effect of key variables were evaluated using a central composite experimental design. The performances of both activators increased with temperature and sodium hydroxide concentration. Also, the performance of the cationic bleach activator increased with activator concentration, while an increase in the concentration of nonanoyloxybenzene sulphonate gave an adverse effect on the performance. It was found that the cationic bleach activator was superior to the anionic activator in the hot bleaching of cotton under the conditions studied.     

Cold pad–batch bleaching of cotton fabrics with a TAED/H2O2 activating system

The cold pad–batch bleaching of cotton fabrics using a tetra acetyl ethylene diamine/hydrogen peroxide (TAED/H₂O₂) activating system is investigated in this study. The effects of key bleaching parameters (hydrogen peroxide dosage, sodium hydroxide dosage, TAED/H₂O₂ mol ratio and batch time) on the bleaching efficiency were investigated by single‐factor analysis and orthogonal experiment analysis. The performance of the activator TAED in the cold pad–batch process was examined and the activating mechanism is discussed. The optimised bleaching recipe and processing conditions are reported, and the optimal activated bleaching process is also compared with a conventional cold pad–batch bleaching process. The results show that the optimised TAED/H₂O₂ activated bleaching system could achieve high quality cotton bleaching with comparable fabric whiteness to the conventional system at much shorter batch times, and with significantly reduced fabric strength loss and decreased alkali consumption, which would be beneficial to sustained development of the textile wet‐processing industry.     

Performance of a new cationic bleach activator on a hydrogen peroxide bleaching system

The performance of a cationic bleach activator, N -[4-(triethylammoniomethyl)benzoyl]caprolactam chloride, was evaluated in a hot peroxide bleaching process. The effect of time, temperature and the concentrations of hydrogen peroxide and activator on the bleaching of cotton fabric was investigated using a central composite experimental design. Temperature was found to be the most significant parameter. By adding the cationic activator it was possible to achieve a level of whiteness comparable to a typical commercial bleaching system but under relatively mild conditions of time and temperature. As a consequence, chemical damage to the fabric could be reduced. The effect of the cationic bleach activator was compared to that of an anionic activator, nonanoyloxybenzene sulphonate. The cationic activator was superior to the anionic activator in bleaching the fabric under the optimised conditions used in the study. Received: 13 January 2004, Accepted: 10 March 2004     

Bleaching Activators and the mechanism of bleaching activation

Bleaching activators are compounds with O- or N-bounded acetyl groups which are able to react with the strongly nucleophilic hydroperoxy anion to yield peroxyacetic acid. The peroxyacetic acid is decomposed in weakly basic media in a bimolecular reaction forming singlet oxygen. The maximum of the decomposition rate of peroxyacetic acid at pH = 8.3 is also the maximum of bleaching activity of systems containing both bleaching activators and sodium perborate; therefore singlet oxygen must play a decisive role in the activated bleaching of textiles during the washing process. Different bleaching activators can be compared both on the basis of their reaction rates with hydrogen peroxide in weakly basic media and on the basis of their reaction rates with piperidine in dioxane. A great number of potential bleaching activators was studied and compared.     

Bleaching Activators as Acylating Agents kinetics of the acetylation of piperidine by some bleaching activators

The bleaching activators 1,5-diacetyl 2,4-dioxo-hexahydro-1,3,5-triazine (DADHT), tetraacetyl ethylenediamine (TAED), tetraacetyl glycolurile (TAGU), N,N′-diacetyl N,N′-dimethyl urea (DDU) and pentaacetyl glucose (PAG) are efficient acetylating agents which convert primary and secondary amines into their N-acetyl derivatives. The rates of the reactions of the bleaching activators mentioned with piperidine were determined in the temperature range 20 to 90°C using dioxane as the solvent. The kinetic constants can be regarded as rough measures of the activity of the bleaching activators.     

Comparison of four oxidants activated through tetraacetylethylenediamine for developing sustainable and rapid degradation of organic dye

Four common oxidants, including hydrogen peroxide (H₂O₂), sodium percarbonate (SPC), sodium perborate (SPB) and sodium persulphate (SPS), were activated with tetraacetylethylenediamine (TAED) to degrade an azo dye, CI Reactive Red 195, in water, for building a novel and rapid oxidative system comprising the merits of cost‐effectiveness and high sustainability. Elevated temperature and high pH level enhanced the activation effect of TAED for accelerating dye degradation. Peracetic acids were confirmed to be the main oxidative species for dye degradation in four TAED/oxidant systems. Hydroxyl radicals and sulphate radicals were also involved in dye degradation in the TAED/SPS system, which showed a stronger oxidative capacity than the other three systems over a wide pH range. More importantly, the addition of inorganic salts or surfactants also favoured the dye degradation in TAED/oxidant systems. Although a slow mineralisation process of the dye was found when the TAED/SPC or SPS system was used, low‐toxic intermediates were detected after the degradation.     

Combination of Surfactant Action with Peroxide Activation for Room-Temperature Cleaning of Textiles

Room-temperature cleaning of textiles is commonly practiced in many countries for energy saving as well as custom in daily life, but not very effective for removing colored contaminants. In this work, it was proposed to combine surfactant action (SA) with peroxide activation (PA) in a peroxide activator to enable cleaning of textiles at room temperature. N-[4-(alkyldimethylammoniomethyl)benzoyl]lactam chloride was designed and synthesized as a prototype of the proposed peroxide activator, in which the alkyl chain with a carbon atom number of n was responsible for surfactant action and the N-benzoyllactam with a carbon atom number of m in the lactam ring was responsible for peroxide activation. Such a peroxide activator was hereby referred to as SAPA_m-n. The room-temperature cleaning performance of SAPA_m-n was examined by cotton fabrics contaminated with morin and waste engine oil, respectively. It was found that SAPA_m-n was able to activate hydrogen peroxide released from sodium perborate so as to effectively bleach the morin-contaminated cotton fabric at room temperature. Though extending the alkyl chain length of SAPA_m-n resulted in no apparent effect on the room-temperature bleaching performance, it enhanced the surfactant action which contributed to removing oily contaminants from textiles. Color-safe performance of SAPA_m-n was evaluated by cleaning a dyed cotton fabric at room temperature. It was found that the peroxide bleach activated by SAPA_m-n resulted in no apparent color change of the dyed cotton fabric. The results of this study provide new insights on textile cleaning at room temperature for the purpose of energy saving.     

过碳酸钠洗涤性能和稳定性能影响因素的研究

过碳酸钠 (PC)是一种碳酸钠与过氧化氢的络合物 ,其特点是对环境无污染。作者以洗涤剂中含有过碳酸钠为前提 ,从洗涤剂最常见的原料对PC的活性与稳定性能的影响方面进行了研究 ,通过实验证明Na2 CO3 、Na2 SO4 、十二烷基苯磺酸钠 (LAS)、三聚磷酸钠 (STPP)、MgSO4 、Na2 SiO3 、四乙酰乙二胺 (TAED)对PC的活性和稳定性都有影响。发现Na2 CO3 对过碳酸钠漂白的促进作用在过碳酸钠质量浓度低的时候尤其明显 ;随着Na2 SO4 、LAS用量的增加 ,白度值上升 ,在达到一定值后白度下降 ;而STPP恰恰相反 ,质量浓度增大 ,白度增大 ,当STPP质量浓度达到一定值时 ,作用反而更显著 ;MgSO4 很敏感 ,在窄区间有一峰值 ;Na2 SiO3 的用量在 2 5 %以内时 ,白度升高的趋势很强 ;TAED对PC起活化作用且和温度有关。最后设计出一个配方与标准粉比较去污比值是 2 2 1。     

Low‐temperature bleaching of cotton fabric using a copper‐based catalyst for hydrogen peroxide

Hydrogen peroxide can be catalysed to bleach cotton fibres at a temperature of 70 °C by incorporating the copper‐based catalyst [Cu(TPMA)Cl]ClO₄·1/2H₂O in the bleaching solution. The effects of pH, temperature, and concentration of catalyst and hydrogen peroxide on bleaching effectiveness were evaluated. The effects of other transition metal complexes of tris(2‐pyridylmethyl)amine were also examined. The bleaching mechanism was investigated by studying the active species. The results showed that a satisfactory whiteness index could be obtained at low temperature with the copper‐based catalyst, and it also had a competitive advantage in protecting cellulose from severe chemical damage. Cu(i )TPMA(OOH)^? was the active species in bleaching.     

Synthesis of novel bleaching catalyst containing macrocyclic manganese complexes and potential applications in laundry detergent

A bleaching catalyst based on manganese complexes, consisting of meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane and racemic-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane ligands, was synthesized and applied at 25°C to cotton fabrics stained with tea, coffee, curry, and sugar beet to examine the bleaching properties. The bleaching performance of this novel catalyst was higher than that of the conventional activator, tetraacetyl ethylenediamine (TAED). Dye and fabric damage were also examined for six differently dyed test fabrics under stressed conditions over 30 wash cycles. The dye damage induced by the catalyst was significantly less than that induced by TAED in direct black 22, reactive blue 225, reactive red 158, and sulfur blue 19. Tensile strength loss measurement, which represents fabric damage, showed less damage for the catalyst in direct black 22, direct blue 71, reactive red 158, and sulfur blue 19. The results indicate that this new bleaching catalyst could potentially be employed for low-temperature bleaching.     

微波辐射与助剂对纸浆漂白的活化作用研究

在碱性麦草浆过氧化氢漂白过程中，利用微波加热，对漂白效果与进程都具有一定意义。另外，酰胺助剂TAED的加入，对双氧水漂白具有明显的改善作用，影响其漂白效果的因素有：TAED与双氧水的摩尔比，温度，时间，pH值及双氧水的用量。在一定限度下，漂浆的白度随这些因素的增加而提高。与此同时可降低漂白温度，缩短漂白时间，这就意味着可以减少能耗。降低生产成本。     

Low‐temperature bleaching of cotton fabric with a binuclear manganese complex of 1,4,7‐trimethyl‐1,4,7‐triazacyclononane as catalyst for hydrogen peroxide

Bleaching of cellulose fabric with hydrogen peroxide is traditionally conducted under alkaline conditions at high temperature, which leads to greater energy consumption and fibre damage. In this study, a binuclear manganese complex of the ligand 1,4,7‐trimethyl‐1,4,7‐triazacyclononane as the catalyst for hydrogen peroxide bleaching was synthesised via a simplified method. Low‐temperature bleaching of cotton fabric with the manganese complex and the effect of key bleaching variables on the bleaching performance were investigated. Hydrogen peroxide could be catalysed to bleach cotton knitted fabric at a temperature as low as 60 °C by incorporating the complex in the bleaching solution. The whiteness index of the fabric bleached at low temperature was lower than that of fabric bleached at high temperature, but the bursting strength retention is much better for the fabric bleached at low temperature. The low temperature is energy‐saving and has environment‐friendly advantages over the traditional high‐temperature method.     

四乙酰乙二胺辅助珍珠漂白的研究

为了加快珍珠的漂白过程,探索了采用四乙酰乙二胺(TAED)作为漂白的活化剂.研究结果表明,TAED对珍珠的漂白具有催化漂白效果,可能是TAED与HOO(-)反应生成乙酸根负离子和二乙酰乙二胺(DAED),反应生成的过乙酸具有比H2O2更强的漂白能力所致,TAED浓度对珍珠表面质量有显著影响.     

Lyocell纤维的漂白工艺

建立了一种应用于Lyocell纤维的新型漂白工艺 分析了漂白液中的过氧化氢质量分数、漂白时间、pH值、漂白温度、稳定剂质量分数对Lyocell纤维的白度和干断裂强度的影响.在确定的漂白工艺四步骤中第一步为预漂白,加入了稳定剂DELINOL9258,增加了漂白效果.漂白步骤最佳优化条件是：过氧化氢质量分数0.8％,漂白时间50 min,漂白液pH值11,漂白温度80℃,稳定剂LAVATEX9188质量分数0.3％     

Synthesis,Characterization, and Toxicological Properties of New Cationic Bleach Activators

Three new bleach activators for cotton containing pyridinium (PBBC), nicotinamido (NABBC), and 3‐methylpyridinium (3‐PBBC) cationic groups were synthesized and characterized by ¹H NMR and HPLC–mass spectrometry. They were then applied to cotton fabric in a bleaching process and evaluated for their performance against the prototype N‐[4‐(triethylammoniomethyl)benzoyl]butyrolactam chloride (TBBC) at a relatively low bleaching temperature (55 °C) and pH 8.5. Measurement of Commission internationale de l’éclairage (International Commission on Illumination) (CIE) whiteness index (WI) values showed that PBBC (WI = 64), NABBC (WI = 58), and 3‐PBBC (WI = 71) impart a significant increase in CIE whiteness compared to a control sample (WI = 40). Among the three new activators, 3‐PBBC exhibited the best performance. Its WI was comparable to that of fabric bleached using the prototype bleach activator TBBC. The acute toxicity of TBBC and the new bleach activators was evaluated using the microcrustacean Daphnia similis. The chronic toxicity of TBBC and 3‐PBBC was evaluated using the green alga Raphidocelis subcapitata, and mutagenicity was evaluated in the Salmonella/microsome assay using the strain TA100. 3‐PBBC was 86 times less toxic to D. similis, 18 times less toxic to R. subcapitata, and 10 times less mutagenic to TA100 in comparison with TBBC.