Preparation of pigmented inkjet ink for six-color printing on silk fabric

This research prepared five sets of pigmented inkjet inks and pretreated the silk fabric with chitosan, glycine and N-[(2-hydroxyl-3-trimethylammonium) propyl] chitosan chloride (HTACC) to enhance print quality. The six pigmented inkjet inks comprising black (Bk), cyan (C), magenta (M), yellow (Y), light cyan (LtC) and light magenta (LtM) colors were prepared with surface-modified pigments and a pigment-to-binder ratio of 1:2. The binder was the copolymer of styrene-acrylic acid emulsion. Different ratios of diethylene glycol and glycerol for verifying the ink viscosity, surface tension with jettability were investigated. The prepared inks had pH in the range of 6.7-8.8, zeta-potential in the range from (-35) to (-50) mV, the pigment particle sizes in the range of 100-300 nm, surface tension in the range of 39 – 46 mN m-1. The black inks prepared by the pigment-to-binder ratios of 1:0, 1:0.5, 1:1, 1:1.5 and 1:2 exhibited both the Newtonian flow at low shear rates (21-142 s-1) and non-Newtonian flow at high shear rates (180-741 s-1). The ink formulation 5 with a pigment-to-binder ratio of 1:2 which was in the jettable range on a viscosity-surface tension criteria map had the viscosity in a range of 2.78 – 3.44 mPa s which jetted the printing pattern completely. The ink formulation 5 was thus best suited for printing with an Epson piezoelectric type inkjet printer. The silk fabric pretreated with chitosan, HTACC, and mixed chitosan and glycine was then each printed with the ink formulation 5. The printed silk fabrics were analyzed for color gamut and color saturation, stiffness, light and wash fastnesses. The printed silk fabrics exhibited that the color gamut and color saturation of the pretreated fabrics provided a wider color gamut than the printed colors on the untreated fabrics. The mixed chitosan and glycine, and HTACC pretreatments enhanced markedly the chroma while the color strength of the fabrics with HTACC pretreatments increased most. The pretreated silk fabrics by chitosan or HTACC did not increase the fabrics stiffness. The light fastness of the pretreated fabrics did not change from the untreated ones, although the wash fastness increased from 4 to 4-5. The extent of coagulation efficiency between the pretreatment reagents and inks was investigated by UV-visible spectroscopy from which HTACC can exhibit strong interaction with the pigments in the inks.本研究制备了五组着色喷墨墨水，并采用壳聚糖、甘氨酸以及N-[(2-羟基-3-三甲基铵基)丙基]壳聚糖氯化物（HTACC）对真丝织物进行预处理，以提升印刷质量。本研究制备了包含黑色（Bk）、青色（C）、品红色（M）、黄色（Y）、浅青色（LtC）以及浅品红色（LtM）共6色的着色喷墨墨水，采用表面改性颜料制备，颜料与粘合剂的质量比为1:2，粘合剂为苯丙乳液共聚物。研究中通过调整二甘醇与甘油的不同配比，对墨水的黏度、表面张力及可喷射性进行考察。所制备的墨水pH值范围为6.7~8.8，Zeta电位（zeta-potential）范围为-35~-50 mV，颜料粒径范围为100~300 nm，表面张力范围为39~46 mN·m⁻¹。当剪切速率为21~142 s⁻¹的低剪切条件下，采用颜料与粘合剂比为1:0、1:0.5、1:1、1:1.5及1:2制备的黑色墨水均表现出牛顿流体特性；而在180~741 s⁻¹的高剪切条件下则呈现非牛顿流体特性。颜料与粘合剂比为1:2的墨水配方5，其黏度范围为2.78~3.44 mPa·s，符合黏度-表面张力判据图中的可喷射范围，可完整喷射出印刷图案，因此最适配爱普生（Epson）压电式喷墨打印机。随后采用墨水配方5分别对经壳聚糖、HTACC以及壳聚糖与甘氨酸混合预处理的真丝织物进行印刷。对印刷后的真丝织物进行色域、色饱和度、硬挺度、耐光色牢度及耐洗色牢度测试分析。经印刷的真丝织物测试结果表明，经预处理的织物其印刷色域与色饱和度均优于未处理织物的印刷表现。壳聚糖与甘氨酸混合预处理以及HTACC预处理均可显著提升织物的彩度，其中HTACC预处理织物的色强度提升最为显著。经壳聚糖或HTACC预处理的真丝织物，其硬挺度并未出现提升。经预处理的织物耐光色牢度与未处理织物基本一致，但耐洗色牢度从4级提升至4~5级。通过紫外-可见分光光度法考察了预处理试剂与墨水间的凝聚效率，结果表明HTACC可与墨水中的颜料产生较强的相互作用。