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    Dyes and Pigments

    Extraction of reactive dyes from aqueous solutions by halogen‐free ionic liquids

    Abstract

    Dyes are commonly used in various industries and unfortunately many of them are discharged into water bodies, causing environmental problems. In the current study, three hydrophobic, halogen‐free ionic liquids were synthesised and their capability as extracting agents was evaluated using four reactive dyes (CI Reactive Blue 4, CI Reactive Black 5, CI Reactive Orange 16 and CI Reactive Red 2). The ionic liquids, immiscible with the aqueous phase, could extract the reactive dyes from aqueous solutions, withdrawing the same amount of weight. The effects of pH and temperature on the extraction process were also studied. Trioctylmethyl ammonium ethylenediaminetetraacetate displayed a high extraction efficiency (99%), where only 33 mg of ionic liquids extracted 50 mg of CI Reactive Blue 4. Fourier Transform–infrared spectroscopy was used to screen the interaction between the ionic liquid and CI Reactive Blue 4 during the extraction stage.

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    Source:: Coloration Technology

          

    Towards the design of a blending system for precoloured fibres

    Abstract

    In order to create a commercial system for blending precoloured fibres that will appear visually solid once combined, it is necessary to understand the maximum colour difference required between the blend components. Based on this understanding, the lowest number of primaries required to populate a given colour gamut can be determined. A series of psychophysical experiments was carried out to explore the colour difference between fibre‐blend components and whether the resulting blended samples are perceived as visually solid. Experiments were carried out with loose stock fibre, yarn and knitted samples. Generally, it was found that the likelihood a blend appeared as visually solid increased as the average colour difference between the blend components, or primaries, decreased. The value of the mean colour difference at which 50% of participants viewed the blend as being visually solid was found to be 20.8, 20.5 and 18.0 for fibre, yarn and knitted samples, respectively. Consequently, it was found that it was more difficult to obtain a solid shade with the knitted form than with the loose stock fibre form.

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    Source:: Coloration Technology

          

    Towards the design of a blending system for precoloured fibres

    Abstract

    In order to create a commercial system for blending precoloured fibres that will appear visually solid once combined, it is necessary to understand the maximum colour difference required between the blend components. Based on this understanding, the lowest number of primaries required to populate a given colour gamut can be determined. A series of psychophysical experiments was carried out to explore the colour difference between fibre‐blend components and whether the resulting blended samples are perceived as visually solid. Experiments were carried out with loose stock fibre, yarn and knitted samples. Generally, it was found that the likelihood a blend appeared as visually solid increased as the average colour difference between the blend components, or primaries, decreased. The value of the mean colour difference at which 50% of participants viewed the blend as being visually solid was found to be 20.8, 20.5 and 18.0 for fibre, yarn and knitted samples, respectively. Consequently, it was found that it was more difficult to obtain a solid shade with the knitted form than with the loose stock fibre form.

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    Source:: Coloration Technology

          

    Determination of the dye penetration rate in porous aluminum oxide using Raman spectroscopy

    Oxidised aluminum coatings are useful in various high technology applications to protect surfaces from negative environmental effects. In this study, aluminum discs and foils of industrial alloys were anodised in a sulphuric acid/oxalic acid electrolyte. Scanning electron microscopy was used to determine the pore diameter, distribution and surface porosity. The anodising procedure was adapted to produce near‐hollow templates on aluminium foil, onto which aqueous solutions of commercial chromium‐complexed anionic azodyes were dropped. Raman spectroscopy was used to detect the penetration of dye compounds based on the most intensive vibrational modes. Each dye was successfully monitored to assess its penetration rate and behaviour in the anodised coating. This method could be applied to characterise newly developed organic dyes for aluminum colouring.

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    Source:: Coloration Technology

          

    Effect of pigment colour on the printing performance of synthetic leather using a ultraviolet‐curable water‐borne polyurethane acrylate binder

    The effect of pigment colours, cyan (C), magenta (M) and yellow (Y), and a blend of these (CMY blend) on the printing performance of synthetic leather using a ultraviolet (UV)‐curable water‐borne polyurethane acrylate binder and two types of photoinitiators was investigated. The curing process was carried out at different radiation doses using gallium and mercury UV lamps in combination. The performance of the prints was evaluated with abrasion resistance, crock fastness, gloss and hardness values and K/S. Chemical changes in the cured film structures due to UV curing were analysed by Fourier Transform–infrared spectroscopy measurements. The highest hardness values for clear and pigmented cured films were obtained with a gallium and mercury lamp combination at the highest energy density (1529 mJ/cm2). The highest K/S was obtained for the sample printed with the formulation including the C pigment and cured under a gallium and mercury lamp combination at low energy density (398 mJ/cm2). The M‐pigmented film displayed the highest hardness and abrasion resistance, whereas lower values were obtained with films pigmented with Y and C, and CMY blend, successively. The highest dry and wet crock values were obtained with the formulation including the M pigment. CMY‐pigmented film showed the highest gloss values at all energy densities. The pigment colour affected the curing degree of printed films due to the different absorption/transmission intervals of each colour in the UV spectrum.

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    Source:: Coloration Technology

          

    Yellow pigment of Metarhizium anisopliae and its application to the dyeing of fabrics

    Microbial dyes have received substantial attention because of their natural environmental protection, simple access, and reduced regional and seasonal restriction. In this work, a microbial dye, the yellow pigment produced by Metarhizium anisopliae, was first studied then applied. The strain produced by the culture was identified, and the conditions for producing yellow pigment were optimised. Further, the stability of M. anisopliae yellow pigment was examined, and the pigment was applied to the dyeing of silk and wool fabrics. The results showed that the homology of the strain with M. anisopliae was 99.98%. In liquid fermentation culture, the optimal carbon source was glucose, and the dosage was 30 g/l. The maximum pigment yield can be obtained by culturing with 4% v/v of inoculation quantity at pH 7 and 30 °C. In addition, the effects of pH, temperature and metal ions on the yellow pigment of M. anisopliae were significant. The optimum dyeing process conditions were dyeing temperatures of 80 °C for silk and 90 °C for wool, with a dyeing time of 60 min. This research developed a novel microbial dye and studied its application for the dyeing of protein fibres.

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    Source:: Coloration Technology

          

    Synthesis and application of KM‐type reactive dyes containing 2‐ethoxy‐4‐chloro‐s‐triazine

    Abstract

    A new kind of hetero‐bifunctional reactive dye containing 2‐ethoxy‐4‐chloro‐s‐triazine, with better activity matching with β‐hydroxyethyl sulphone sulphate at a low fixation temperature, was successfully synthesised and characterised. An ethoxy group was designed to be introduced into triazine to increase the substantivity and the reactivity of the dyes. Thereby, the fixation of mono‐s‐chlorotriazine/hydroxyethyl sulphone sulphate (KM‐type) bifunctional reactive dyes on cotton was improved, and dyeing under mild conditions with high fixation was realised. Nineteen dyes with orange, red and blue colours were synthesised and characterised by UV‐Vis and infrared spectroscopy and mass spectrometry. Synthesised dyes were dyed at 60, 75 and 90°C, respectively. Exhaustion and reactivity for all of the ethoxy‐containing KM‐type dyes was over 90% at the optimal temperature, and fixation was over 87%, which was higher than the ethoxy‐free comparative dyes. The optimal fixation temperature of ethoxy‐containing dyes was initially reduced to 75°C, and then to 60°C. Compared with comparative dyes, the wash fastness and light fastness were basically unchanged, and the wet rub fastness of the H‐acid series was reduced by one grade.

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    Source:: Coloration Technology

          

    Poly(methyl methacrylate)/polysiloxane core‐shell latex as a deepening agent for dyed polyester fabric

    Abstract

    Polyester fabrics are usually difficult to dye deeply due to their high refractive indexes. In this study, poly(methyl methacrylate)/polysiloxane core‐shell latex was used as a deepening agent in the colour‐deepening finishing of dyed polyester fabrics by lowering the refraction index and enhancing the diffuse reflection via the rough surface. Poly(methyl methacrylate)/polysiloxane core‐shell latex has a better shade‐deepening effect than polysiloxane latex on dyed polyester fabrics. The mass ratio of core/shell monomer and the finishing conditions of the polyester fabrics had a large influence on shade deepening. The optimum finishing conditions were obtained for a mass ratio of core/shell monomer of 1:2, a deepening agent concentration of 10 wt%, a pick‐up of 80%, and a curing temperature of 180°C. After a deepening finishing, the dyed polyester fabrics showed a small colour difference and the colour fastness barely decreased.

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    Source:: Coloration Technology

          

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