David Hinks

Evaluating Hydrogen Peroxide Bleaching with Cationic Bleach Activators in a Cold Pad-Batch Process

Bleach activators generate peracids in the presence of hydrogen peroxide and alkali that are more potent oxidizing agents than hydrogen peroxide under comparable bleaching conditions. The effects of key bleaching parameters (activator concentration, hydrogen peroxide, chelant, and pH) on the performance of cold pad-batch bleaching on cotton are investigated. Optimized recipes are determined for two cationic activators, N-[4-(triethylammoniomethyl) benzyl]ca prolactam chloride and 6-(N,N,N-trimethylammonio) hexanoyl caprolactam p-toluenesulfo nate, using a central composite experimental design. The laboratory optimized conditions are used for pilot plant scale bleaching of cotton knit fabric. CIE whiteness index values are calculated from measured reflectance data of the pilot scale bleaching and are in close agreement with those predicted by the experiment. A high level of whiteness (CIE WI > 70) is achieved for both activators with 8-hour batching, and measurements of the degree of polymerization of the bleached and greige fabrics show little fiber damage in each case.

Synthesis and evaluation of organic pigments and intermediates. 1. Nonmutagenic benzidine analogs

Abstract The design, synthesis, characterization, and genotoxicity of 4,4′ diaminobiphenyl (benzidine) analogs with substituents in the 3,3′ and/or 2,2′ positions are reported. Analogs containing bulky substituents in the 3,3′ positions significantly reduce or eliminate mutagenic activity, while substituents in the 2,2′-positions increase the dihedral angle across the biphenyl linkage––a property that can be utilized in the design of novel nonmutagenic colorants. 2,2′-Dimethylbenzidine was found to be mutagenic in both the standard Salmonella mammalian mutagenicity assay (Ames test) with metabolic acitivation and the preincubation assay protocol. 2,2′-Dichloro-5,5′-dipropoxybenzidine, 2,2′-dimethoxy-5,5′-dipropoxybenzidine and 2,2′-dimethyl-5,5′-dipropoxybenzidine were nonmutagenic in both assays. The corresponding bis-acetoacetamido derivatives of the latter two compounds were also nonmutagenic. Good yields with minimal purification were obtained for certain diamines, providing potentially useful nongenotoxic intermediates in the synthesis of bisazo and bisazomethine dyes and pigments.

Direct analysis of textile fabrics and dyes using infrared matrix-assisted laser desorption electrospray ionization mass spectrometry.

The forensic analysis of textile fibers uses a variety of techniques from microscopy to spectroscopy. One such technique that is often used to identify the dye(s) within the fiber is mass spectrometry (MS). In the traditional MS method, the dye must be extracted from the fabric and the dye components are separated by chromatography prior to mass spectrometric analysis. Direct analysis of the dye from the fabric allows the omission of the lengthy sample preparation involved in extraction, thereby significantly reducing the overall analysis time. Herein, a direct analysis of dyed textile fabric was performed using the infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) source for MS. In MALDESI, an IR laser with wavelength tuned to 2.94 μm is used to desorb the dye from the fabric sample with the aid of water as the matrix. The desorbed dye molecules are then postionized by electrospray ionization (ESI). A variety of dye classes were analyzed from various fabrics with little to no sample preparation allowing for the identification of the dye mass and in some cases the fiber polymer. Those dyes that were not detected using MALDESI were also not observed by direct infusion ESI of the dye standard.

Unique-hue stimulus selection using Munsell color chips

Presented are intra- and inter-observer variability data comparing the unique-hue (UH) selections of sets of males and females, using two different visual experimental procedures incorporating Munsell color chips of varying hue but identical chroma and value. Although 34 of the 40 Munsell hue chips were selected by at least one observer as a UH, selections were generally repeatable. In addition, intra-observer variability represented approximately 15% of inter-observer variability. Also, when only three consecutive Munsell chips were viewed at a time, females showed significantly larger intra-observer variability than males, especially when making unique green selections. However, variability in UH selections was statistically insignificant between males and females when all Munsell chips were viewed simultaneously. No correlation was found between UH selections or intra-observer variability and hue ordering ability.

Notes on the application of the standardized residual sum of squares index for the assessment of intra- and inter-observer variability in color-difference experiments

The standardized residual sum of squares index was proposed to examine the significant merit of a given color-difference formula over another with respect to a given set of visual color-difference data [J. Opt. Soc. Am. A 24, 1823-1829, 2007]. This index can also be employed to determine intra- and inter-observer variability, although the full complexity of this variability cannot be described by just one number. Appropriate utilization of the standardized residual sum of squares index for the assessment of observer variability is described with a view to encourage its use in future color-difference research. The main goal of this paper is to demonstrate that setting the F parameters of the standardized residual sum of squares index to 1 results in a loss of essential properties of the index (for example, symmetry), and is therefore strongly discouraged.

Reducing problems of cyclic trimer deposits in supercritical carbon dioxide polyester dyeing machinery

Abstract The present paper describes an alternative procedure for the reduction or elimination of oligomeric polyester residues, in particular the cyclic trimer (CTR), in supercritical fluids (SCFs). Polyethylene terephthalate is the largest, (by volume) man-made synthetic fiber produced in the world owing to its favorable properties, such as durability, strength, stability during heat setting, abrasion resistance, and resistance to sunlight, acids, alkalis, and bleaches. In addition, polyester fibers have very good crease recovery and are durable to washing. Because of these characteristics, polyester has many important uses including home furnishings, apparel fabrics, automotive interior fabrics, and carpeting (Ind. Eng. Chem. Res. 39 (2000) 4806). Due to the large volume of polyester dyed, fundamental research has given attention to alternatives for conventional aqueous processes. The application of SCFs, especially supercritical carbon dioxide (SC-CO2), in the textile industry has recently become an alternative technology for developing a more environmentally friendly dyeing process. SCF dyeing technology has the potential to overcome several environmental and technical issues in many commercial textile applications such as yarn preparation, dyeing and finishing. SCFs represent a potentially unique media for either transporting chemical into or out of a polymeric substrate, because of their thermo-physical and transport properties. SCFs exhibit gas-like viscosities and diffusivities and liquid-like densities. Carbon dioxide is appealing for use as a SCF because it is inexpensive, non-toxic, non-flammable, environmentally friendly, and chemically inert under many conditions (J. Org. Chem. 49 (1984) 5097). In order to improve efficiency and address some of the environmental concerns with SCF technology, researchers at North Carolina State University (NCSU), College of Textiles, have constructed a single-package-pilot-plant system for dyeing polyester using SC-CO2. Based in part on data gathered from this investigation, the technical and economic feasibility of this process has been demonstrated and SCF dyeing appears to be on the leading edge of emerging technologies. However, it has been shown that the removal of precipitated oligomers mainly from the inside walls of all parts of the dyeing machine (i.e. vessels, spindle tube, sight glasses, valves, tubing, and fittings) is highly desirable. Experimental pressure measurements across a few sections of the SC-CO2 dyeing machine show that significant pressure losses can occur where oligomer, predominately CTR, builds up. Consequently, the maximum CO2 volume flow rate in the dyeing machine can decrease 30–35% (Conf. Eng. Note (1998); Conf. Eng. Note (1999)). A preliminary investigation shows that highly insoluble CTR has a reduced affinity to adhere to these stainless steel surfaces at higher SC-CO2 pressure. Although the knowledge and expertise base in this new textile research area has been increased considerably, an economic removal procedure for CTR in SC-CO2 machinery has not been found (Proc. 6th Conf. Supercrit. Fluids Appl. (2001) 571).

Synthesis and evaluation of organic pigments.: 3. Studies based on nonmutagenic twisted benzidines

Abstract Bis-chromophoric pigments prepared using nonmutagenic benzidine analogs with high dihedral angle across the biphenyl linkage are reported. The mutagenic properties of twisted bisazomethine, disazoacetoacetanilide, disazopyrazolone, disazobenzimidazolone and disazonaphthol pigments were established using the standard Ames Salmonella mammalian mutagenicity assay and the Prival modification. Results from these tests and from the evaluation of hue, color strength and photostability of the pigments prepared are reported. Some of the new pigments are potential viable alternatives to those derived from 3,3′-dichlorobenzidine and other genotoxic analogs of benzidine.

Synthesis and evaluation of organic pigments.: 2. Studies of bisazomethine pigments based on planar nonmutagenic benzidine analogs

Abstract The synthesis, characterization, genotoxicity and light fastness of thio- and oxopyrimidine based bisazomethine pigments prepared from a series of nonmutagenic benzidine congeners is reported. Whereas bisazomethine pigments based on benzidine and 3,3′-dimethylbenzidine were mutagenic in both the Ames assay and the Prival modification of the Ames assay, incorporation of bulky (>C 2 ) alkyl and alkoxy groups in the 3,3′- positions of the benzidine moiety gave nonmutagenic bisazomethine pigments.

Genotoxicity of azo dyes: Bases and implications

Genotoxicity is a general term employed by genetic toxicologists when referring to adverse interactions between DNA and various substances to produce a hereditable change in the cell or organism. In humans, such changes are associated with birth defects, carcinogenesis, teratogenesis, and other types of diseases. It is generally believed that interactions with DNA which cause mutations to occur constitute the early events leading to hereditable changes. Consequently, much of the experimental work in this area has been devoted to mutagenicity testing. This approach is used as a cost-effective and relatively quick way to predict the potential carcinogenicity of organic substances. Although the genotoxicity of azo dyes has been the subject of numerous publications since the carcinogenicity of benzidine towards humans was first confirmed, this subject continues to be extremely important. It is interesting to note, however, that very little of the reported work on this subject appears to be aimed at developing data useful to dyestuff chemists in the design of non-genotoxic dyes. Rather, it is evident that much of the generated data are intended for use in formulating databases that can be used by regulatory agencies in predicting the potential health risks of proposed (new) and existing commercial dyes. This chapter, while by no means presented as an exhaustive treatment of the subject, contains a summary of recent literature, along with examples of how this information has been used to design non-mutagenic azo dyes and aromatic amines, and will be presented more from the perspective of a dyestuff chemist rather than a genetic toxicologist.

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.