Thermodynamic and kinetic parameters of polyester dyeing with Disperse Blue 56 using bio-based auxiliaries and co-solvent microemulsion

  UPCommons Portal del coneixement obert de la UPC http://upcommons.upc.edu/e-prints Aquesta és una còpia de la versió author’s final draft d'un article publicat a la revista Textile research journal . URL d'aquest document a UPCommons E-prints: http://hdl.handle.net/2117/170498 Article publicat / Published paper : Radei, S. [et al.]. Thermodynamic and kinetic parameters of polyester dyeing with Disperse Blue 56 using bio-based auxiliaries and cosolvent microemulsion. "Textile research journal", 2019, vol. 90, núm. 5-6, p. 523-536. Doi: 10.1177/0040517519871264 1  Thermodynamic and kinetic parameters of polyester dyeing with Disperse Blue 56 using biobased auxiliaries and co-solvent microemulsion Abstract The study aims to dye a polyester fabric with a low molecular weight anthraquinone type disperse dye (C.I. Disperse Blue 56), n-butylacetate as co-solvent in the microemulsion system and the presence of two bio based auxiliaries (o-vanillin and coumarin) at temperatures lower than 100ºC. In order to investigate the influence of the temperature and the aforementioned auxiliaries on the kinetic dyeing process, the energy of the activation by the kinetic rates constants were determined. The activated entropy by the theory of absolute rates of dyeing and diffusion of the activated state of the dye for the disorder state of the dyeing system were obtained. Higher activated energies, and higher activated entropy so higher dye absorption for polyester samples dyed with o-vanillin/n-butylacetate than polyester samples dyed with coumarin/nbutylacetate were found. Color strength values of the polyester fabric dyed for this proposed micro-emulsion dyeing system at low temperature (95ºC) and the polyester fabric dyed with conventional dyeing system at high temperature (135ºC) were similar. According to color fastness to washing and ironing, it was found that the use of these auxiliaries did not modify the fastness values of the dyed samples significantly.  Keywords: Polyester, dyeing kinetic, apparent activation energy, coumarin, o-vanillin, n-butylacetate, microemulsion dyeing 2  1. Introduction The kinetic dyeing microemulsion system of the polyethylene terephthalate (PET) with disperse dyes at lower temperatures than conventional dyeing process with the cosolvent (n-butylacetate) were studied previously [1,2]. In this sense due to growing environmental concerns, there has been significant interest in dyeing polyester with carriers or additives at lower temperatures, considering their biodegradability, low toxicity and environmentally friendly practices [1-3]. With the aim of saving water and energy, Gao et al, 2018 proposed an environmentally friendly dyeing process, using silicone nanomicelle technique, which the organic silicone oil was used as nano-emulsion by solvent evaporation, this technique improved the dyeability of the polyester compared to polyester dyed by the traditional dyeing system which requires more energy consumption [4]. Parvinzadeh Gashti and Moradian, 2011 prepared PET/Clay nanocomposite via melt spinning system, and the study confirmed that the presence of the clay on polyester increased the dyeability of the polyester by reducing the glass transition temperature of the PET. This method avoids the disadvantages of the toxic carriers [5]. Additionally, Parvinzadeh Gashti et al, 2015 modified the surface of the polyester by corona discharge ionization process. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and reflectance spectroscopy (RS) proved that the corona discharge improved the surface functionality and dyeability of the polyester [6]. Pasquet et al. 2013 dyed polyester fabric with oand p-vanillin in the presence of two disperse dyes (C.I Disperse Blue 56, and C.I Disperse Blue 79) with ethanol as cosolvent. The study confirmed that color strength of the polyester dyed with these auxiliaries was good, mainly when o-vanillin was used [7]. 3  Radei et al [2,3] proposed the use of two alternative bio-based auxiliaries such as orthovanillin (o-vanillin) and coumarin with n-butylacetate as a co-solvent, in the microemulsion system for the high molecular disperse dyes (C.I. Disperse Blue 79 and Disperse Red 167) [3]. This new proposed microemulsion system has advantages such as using biodegradable and non-toxic auxiliaries during the dyeing process. Furthermore, the dyeing system is favorable from both economic and environmental point of view. The microemulsion system is formed with micro particles containing the co-solvent, the dyes and the auxiliaries used, and these micro particles including the dye molecules facilitate the transport to the fiber in function of the temperature used [3,8]. Many studies have been done on kinetics and thermodynamic parameters of polyester dyeing processes in the equilibrium state; however, there is a lack of data related to the thermodynamic parameters before the equilibrium state for improvement the exhaustion and levelness during the kinetic dyeing process [9-11]. The aim of this paper is to study the dyeing process of a polyester fabric with a low molecular weight anthraquinone type disperse dye (C.I. Disperse Blue 56), with nbutylacetate as co-solvent (low environmental impact) in the microemulsion system and the presence of two bio based auxiliaries (o-vanillin and coumarin) at temperatures lower than 100ºC. In order to investigate the influences of the temperature and the aforementioned auxiliaries on the kinetic dyeing process, the energy of the activation by the kinetic rates constants were obtained. The activated entropy was calculated by the theory of absolute rates of dyeing and diffusion in the activated state. This entropy was obtained by rate kinetic and diffusion dyeing values, such were obtained by other authors [12; 13, 14]. The theory of absolute rates of dyeing has advantages for explanation of absorption kinetic dyeing system in the activated state. The quality of the dyed fabrics was evaluated by determining color fastness to ironing and washing. 4  2. Experimental 2.1 Materials 2.1.1. Fabric A standard plain-woven 100% polyester fabric, Type 30 A, from Testgewebe GmbH (Germany) (ISO 105-F10) was used as textile substrate. The average fiber diameter of the fabric was 10µ. 2.1.2 Chemicals and auxiliary products Antraquinone type low molecular weight disperse dye Foron Blue E-BL supplied by Archroma GmbH (Germany) (C.I. Disperse Blue 56, M W = 365.18 g·mol –1 ) was used as a dye. As a co-solvent pure n-butylacetate from Panreac (Spain) (boiling point 126 ºC) was used. Coumarin (M W = 146.15 g·mol –1 ) and o-vanillin (M W = 152.15 g·mol –1 ) with 99% purity supplied by Acros (USA) were used as bio-based auxiliaries, respectively. The chemical structure of the co-solvent, the disperse dye and the two selected auxiliaries are indicated in Figures 1, 2, 3 and 4 respectively.  Figure1. n-butylacetate, CAS NO. 123-86-4  5  Figure2.C.I. Disperse Blue 56, CAS NO. 12217797  Figure 3. Coumarin (2H-chromen-2-one), CAS No. 91-64-5   Figure 4. O-vanillin (2-hydroxy-3-methoxybenzaldehyde), CAS No. 148-53-8 Hostapal NF liq a non-ionic surfactant supplied by Archroma was used for the predyeing washing. Eganal RAP liq supplied by Archroma (Germany) as a dispersing agent was used. Sodium hydrosulphite (MW = 174.11 g·mol –1 ) and analytical-grade sodium hydroxide, both supplied by Panreac, were used for the post reductive washing. N,NDimethylformamide (DMF) with 99.8% purity supplied by Panreac (Spain) was used to extract the dyestuff from the fabric. 2.2. Isothermal dyeing procedure The dyeing procedure was performed as described by Radei et al. 2018. The standard polyester fabrics were pre-washed (40 ºC for 30 minutes) with 2 g/L of Hostapal NF liq, then rinsed with distilled water and dried at room temperature. Afterwards, fabrics were dyed with 2% o.w.f of disperse dye, 4% o.w.f. of auxiliaries (o-vanillin or coumarin) and 16.66 g/L of n-butylacetate as a co-solvent. Bath ratio was fixed at 1:60. An isothermal dyeing process was performed at four temperatures (65, 75, 83 and 95 ºC) for 120 minutes, except for the lower temperature (65 ºC), which the time was 150 6  minutes. The dyeing process was performed in a Linitest MTT dyeing machine, Atlas MTT GmbH (Germany).  Post reductive washing was done to remove the adsorbed dye at the surface with 0.5 g/L of sodium hydroxide and 2 g/L of sodium hydrosulphite in distilled water (bath ratio 1:50) at 50 °C for 30 min, followed by rinsing three times with cold distilled water, and drying at room temperature for 24 h. Figure 5 shows an Scheme of the experimental procedure followed in this research.  Figure 5. Scheme of the procedure for low dyeing temperature dyeing polyester 7  2.4. Particle size measurement Average values of dye baths particle size were determined with a Zetasizer nano series (Malvern, UK) device at 90° with respect to the incident laser beam at 25 °C. Quartz cells 1 cm thick and volume of 4 mL were used. 2.5. Dye absorption measurement Dye absorbed by the dyed polyester fabric was determined via extraction with DMF. Maximum absorbance was measured at λmax= 640 nm for C.I Disperse Blue 56. A model M 330 UV–Visible spectrophotometer Camspec (UK) was used. The equation (1) shows the linearity of the Beer-Lambert law for C.I. Disperse Blue 56 at different concentrations related to their maximum absorbance [15]. (Abs) λmax 640nm= 15.383[Df] (1) where Df is the dyestuff concentration in the fiber (mg dye/g fiber) and (Abs) λmax 640nm is the maximum absorbance . The correlation coefficient was R2= 0.9982  Experimental values for the amount of the dye extracted from fiber during the kinetics dyeing process were calculated based on the equation 1. 2.6. Colorimetric curves analysis Colorimetric curves were determined using a spectrophotometer Datacolor SF600 plusCT. The values were obtained from the average of four individual measures rotating 90º the fabric measured, the illuminant D65, and observer 10º were used.  8  2.7. Differential scanning Calorimetry (DSC) Differential scanning calorimetry (DSC) tests performed on a Perkin Elmer DSC 7 to determine changes on thermal characteristics of dyed samples. 4mg samples were heated from 40ºC to 300ºC at a heating rate was 20°C/ min. 2.8. Color fastness The color fastness to ironing was analyzed according to the UNE-EN ISO 105-X11 method, at three temperatures (110, 150 and 200°C). Color fastness to washing was tested according to the UNE-EN ISO 105-C06 standard using A2S test stated in the standard. Dyed polyester samples were washed with ten steel balls with and IEC 60456 Base Detergent Type A 2g/L at 40°C for 30 min, bath ratio was 1:50. ATLAS LAUNDER-OMETER GmbH (Germany) was used for the washing test, with a vessel of 550ml. 3. Results and Discussion 3.1. Solubility parameters of auxiliaries, co-solvent, water and polyester used To study whether the auxiliaries used have the capacity to penetrate inside the fabric, solubility parameters (cohesion energy parameters) were calculated for polyester, ovanillin, and coumarin with water as the main solvent and n-butylacetate as the cosolvent. The classic Hansen’s formula (equation 2) for solubility parameters was used, where the total parameter is broken down into contributions from the forces involved [16,17].  ₊₊ (2) In which δd, δp and δh are the contributions from dispersion forces, polar forces, and hydrogen bonding respectively. 15  difference on the K/S values at the maximum wavelength and exhaustion for the microemulsion system at 95ºC and the conventional system at 135ºC. Table 4. K/S values at =630 nm, exhaustion percentage and photographic images of the polyester fabrics dyed with o-vanillin and co-solvent at 95 ºC after 120 minutes and the ones obtained with the same fabric subjected to a conventional dyeing process at 95ºC and 135 ºC in presence of 2 g/L of dispersing agent Eganal. Dyeing time=120 minutes K/S (=640 nm) Exhaustion (%) Photographic image of the dyed fabrics PET dyed with Disperse Blue 56 and in presence of o-vanillin in nbuthylacetate at 95 ºC (microemulsion system) 16.20 97.5 PET dyed with Disperse Blue 56 and in presence of Eganal at 135 ºC (conventional system) 16.81 99.1 PET dyed with Disperse Blue 56 and in presence of Eganal at 95 ºC (conventional system) 4.63 29.1  From these results, it can be concluded that the dyeing process presented in this paper (using a co-solvent/o-vanillin at 95 ºC) gives color strength similar to a conventional process at 135ºC, after the reductive washing, in both cases. This means that with this new process it is possible to reach 97.5% exhaustion with only a slight color difference with respect to the dyeing process at 135 ºC, with a reduction of the dyeing temperature by 40ºC. This new system allows saving thermal energy and makes it possible to perform the dyeing process in open equipment and, in the case of dyeing blended fibers, 16  significantly reduces the risk of damaging the fibers with low resistance to high temperature. These facts demonstrate that the process presented can be appropriate for industrial applications and can be a green alternative method for the industry. 3.6. Diferential Scanning Calorimetry (DSC) analysis In Figure 10 the DSC curves of the dyed fabrics with o-vanillin/co-solvent at 95 ºC, with coumarin/co-solvent at 95 ºC, compared with the ones dyed with the conventional system at 95ºC and 135ºC and the undyed fabric. The parameters obtained from these curves are presented in Table 5.  Melting Pea k 1st transition _____PET dyed with Eganal 135ºC _____PET dyed with o-vanillin/n-butylacetate _____PET dyed with coumarin/n-butylacetate _____ PET dyed with Eganal 95ºC _____ PET undyed _____PET dyed with Eganal 135ºC _____PET dyed with o-vanillin/n-butylacetate _____PET dyed with coumarin/n-butylacetate _____ PET dyed with Eganal 95ºC _____ PET undyed 17  Figure 10. DSC endotherms of the of the dyed fabrics with o-vanillin/co-solvent at 95 ºC, with coumarin/co-solvent at 95 ºC, compared with the ones dyed with the conventional system at 95ºC and 135ºC and the undyed fabric: top) zone from 80ºC to 220ºC and down) zone from 220ºC to 280ºC. Table 5. DSC parameters of undyed polyester and polyester samples dyed in different conditions. Parameters Original white sample Conventional dyeing at 95 ºC Dyed with coumarin/cosolvent at 95 ºC Dyed with ovanillin/cosolvent at 95 ºC Conventional dyeing at 135 ºC Thermal transition 1 ∆H (J/g) 3.234 5.216 7.524 6.280 6.688 Melting peak ∆H (J/g) 61.092 57.645 57.528 57.392 58.067  As indicated in Table 5 and Figure 9, in general, the presence of o-vanillin and coumarin did not modify significantly the thermal characteristics of the dyed fabrics and the co_____PET dyed with Eganal 135ºC _____PET dyed with o-vanillin/n-butylacetate _____PET dyed with coumarin/n-butylacetate _____ PET dyed with Eganal 95ºC _____ PET undyed 18  solvent is responsible for changes on the microstructure of the fiber. Regarding the first thermal transition (Figure 10a), which is ascribed to a premelting endothermic peak, the conventional dyeing system without auxiliaries at 95 ºC and 135ºC gives an enthalpy of 5.2 J/g of 6.7 J/g respectively. This means that an increase of 40 ºC in the dyeing temperature increased the enthalpy of this transition around 28.2%. Comparing the polyester dyed with conventional system without auxiliaries at 95 ºC to polyester dyed with auxiliaries at 95 ºC it was observed that the enthalpy of this first thermal transition increases around 44% in the case of the coumarin, and by 20% in the case of the ovanillin, as indicated before this reveals that n-butylaceate affected on the microstructure of the dyed fibers. Based on the melting peak, as shown, the dyeing treatments have not significantly modified the enthalpy and the maximum temperature of the melting peak. The only observed changes are on the shape of the endotherm, which is wider for the dyed samples. This is related with changes on the crystals formed as a consequence of the hydrothermal dyeing treatment. 3.7. Thermodynamic parameters Since in this work is intended to obtain the influence of temperature in the dyeing process of microemulsified dispersed dyes in the presence of the biobased auxiliaries studied at temperatures below 100ºC, values of dyeing rate constant, apparent activation energy, apparent diffusion coefficient, enthalpy and entropy for the polyester samples dyed have been calculated by the theory of absolute rates of dyeing and diffusion of the activated state of the dye molecule [12-14]. 19  3.7.1. Dyeing rate constant To calculate the dyeing rate constant from the initial exhaustion values presented in Table 3, equation 3 was used [20,21]  󰇛󰇜0.5ln󰇛󰇜 󰇛󰇜  (3) where x is the quotient between the dye concentration on the fiber in time t and the initial dye concentration in the dye-bath (Ct/C∞), k is the dyeing rate constant, and t is the time [22]. The values of the dyeing rate constants calculate from the linearity adjustment of the equation 3 are shown in Table 6. Table 6. Absorption rate constant (k) for polyester samples dyed with C.I. Disperse Blue 56, coumarin or o-vanillin and n-butylacetate at 65 ºC, 75 ºC, 83 ºC, and 95 ºC. coumarin o-vanillin T (ºC) k (min-1) k (min-1) 65 0.0148 0.0139 75 0.0282 0.1077 83 0.1859 0.7654 95 0.3207 5.6561 20  As expected, the dyeing rate constant increased as the dyeing temperature increased and generally, except for 65ºC, values of the dyeing rate constant obtained for the polyester dyed with o-vanillin were considerably higher than the values obtained for the polyester dyed with coumarin. Significantly highest value of dyeing rate constant was obtained at 95 ºC for polyester dyed with o-vanillin. This is related with a very fast kinetic dyestuff absorption in all studied times and after 120 minutes of dyeing process, the absorption of dyestuff in the fiber was almost reached to the maximum theoretical concentration. 3.7.2. Apparent activation energy The apparent activation energy of the dyeing process was calculated from the Arrhenius Law, indicated in logarithm form in equation 4 [23]. lnk = lnk0   (4) where k is the dyeing rate constant, k0 is the pre-exponential factor (slope of the line), E is the apparent activation energy, T is the absolute temperature and R is the constant of ideal gases. Values of apparent activation energies obtained from the linear adjustment of equation 4 are shown in the Table 7. Table 7. Values of apparent activation energy for polyester samples dyed with C.I. Disperse Blue 56, coumarin or o-vanillin and n-butylacetate. Polyester dyed with CI Disperse Blue 56, coumarin/ n-butylacetate Polyester dyed with CI Disperse Blue 56, o-vanillin/ n-butylacetate Activation Energy (Kcal·mol–1) Correlation coefficient Activation Energy (Kcal·mol–1) Correlation coefficient 25.34 0.9383 51.05 0.9879 21  As shown in Table 7, the values of apparent activation energy obtained for polyester dyed with o-vanillin/n-butylacetate is higher than polyester samples dyed with coumarin/n-butylacetate. This is because polyester dyed with o-vanillin/butylacetate during the absorption kinetic process was more influenced by the variation of the temperature; with higher value of activation energy than coumarin/n-butylacetate [24]. Values are almost in the same ranges to those previously achieved in the polyester dyeing at equilibrium [22]. 3.7.3. Apparent diffusion coefficient In order to determine the apparent diffusion coefficient, Crank’s equation was used (equation 5) [25, 26].  Ct  2󰇛 . 󰇜. (5)  where Ct is the concentration of dye inside the fabric in the examined time by using the kinetic equation (3), C∞ is the maximum theoretical concentration inside the fabric, t is the time examined, D is the apparent diffusion coefficient and A is the specific surface area (per gram) of the studied fiber. The specific surface using the equation 6 was obtained. After surface divided by weight and after simplification for using µ such as diameter of fiber, following equation was applied for obtaining the specific surface area of the fiber. A104 . (6) Where s is the perimeter of 1 g. length (cm), w is the 1 g. weight (g), ρ is density (/g) and d (applied in µ) is the diameter of the studied fiber respectively. 22  Values of apparent diffusion coefficients obtained from the equation (5) are shown in the Table 8.  Table 8. Apparent diffusion coefficients for polyester samples dyed with C.I. Disperse Blue 56, coumarin or o-vanillin and n-butylacetate Apparent diffusion coefficient (D) (10  ⁄) Disperse Blue 56 T (ºC) Polyester dyed with CI Disperse Blue 56, coumarin/ nbutylacetate Polyester dyed with CI Disperse Blue 56, o-vanillin/ nbutylacetate 65 0.765 ± 0.04 0.531 ± 0.16 75 0.923 ± 0.04 1.241 ± 0.44 83 1.833 ± 1.24 2.216 ± 1.41 95 2.072 ± 0.98 3.775 ± 2.85 As expected, apparent diffusion coefficients increased with increasing temperature. Moreover, polyester samples dyed with o-vanillin lead to higher diffusion coefficients than coumarin/n-butylacetate at all of the temperatures studied. The highest diffusion coefficient was found for polyester dyed in presence of o-vanillin at 95 ºC. According to the definition of diffusion coefficient of the activated dye molecule, it can be concluded that the dyestuff penetration in the polyester samples dyed with o-vanillin is faster compared to the polyester samples dyed with coumarin/n-butylacetate. These values are in good agreement with previous studies for polyester dyeing [22, 24]. 3.7.4. Enthalpy and Entropy of activation The enthalpy and entropy of activation were calculated from the equations 7-12 respectively; by the theory of absolute rates of dyeing of Eying equations were used. [27-32]. D= λ..  . e -∆G*/RT (7) 23  ∆G * = Δ H* - T Δ S* (8) ∗= ED – RT (9) D* = λ. . e∆S*/R . e-∆H*/RT (10) D =D0.e-ED /RT (11) D0 = λ.. . e∆S*/R (12) After simplification and deduction of the aforementioned equations we have reached to the equation 13 for calculating the entropy of activation. ∗ R [ln D0 + ln λ. 1󰇠 (13) where ∗is enthalpy of activation, ∗ is entropy of activation, ED is the activation energy of the diffusion, T is the absolute temperature; R is the constant of ideal gases, h is Planck constant, k is Boltzmann constant, is the distance between two consecutive positions of the molecule diffused in the reaction coordinate (10 Ǻ). D is the apparent diffusion coefficient at 95 ºC and D0 is the slope of the line which was obtained from the linear adjustment of equation 7. The values of D0 for dyed PET samples with coumarin/n-butylacetae and o-vanillin/nbutylacetate were 1.978 and 3.544 Kcal·mol–1 respectively. Table 9 shows the values of entropy and enthalpy of activation calculated from the theory of absolute rates of dyeing and diffusion of the activated state of the dye molecule with the aforementioned equations. 24  Table 9. Entropy and enthalpy and of activation for polyester samples dyed with C.I. Disperse Blue 56, coumarin or o-vanillin and n-butylacetate at 95ºC Activated state polyester dyed with auxiliary products in microemulsion systems ΔS* (Kcal·mol–1K-1) ΔH* (Kcal·mol–1) T=95 ºC T=95 ºC C.I. Disperse Blue 56 (0.333 g/L) polyester dyed in microemulsion: coumarin/n-butylacetate/water (0.666/16.666g/L) 0.01305 3.19 polyester dyed in microemulsion: ovanillin/n-butylacetate/water (0.666/16.666g/L) 0.01422 6.30 As shown, the enthalpy of activation obtained for polyester dyed with disperse dye C.I. Disperse Blue 56 with o-vanillin/n-butylacetate microemulsion at 95 ºC was significantly higher than polyester dyed with coumarin/n-butylacetate microemulsion. 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