Crystallization and Dispersion of Micronized Organic Colorants from Microemulsions
Date Issued
2010
Date
2010
Author(s)
Wu, Tzu-Chin
Abstract
Organic colorants are essential for production of paints, inks and toners etc. The reduction of particle size would improve the stability, color strength, contrast, and transmittance. In this study, we apply two microemulsion systems (o/w、w/o) incorporated with temperature changing process and solvent diffusion process to micronize and disperse four colorants: Disperse Red 60、Pigment Red 177、Pigment Green 36、Pigment Blue 15:6.
Based on the scanning electron microscope (SEM) results, the sizes of disperse red 60 were dramatically reduced to 3.5*1(length*width)~5*1μm and 2*0.6~5*1.3μm by temperature changing process in water / Benzyl alcohol / SDS and DMSO / Cyclohexane / AOT system respectively, which the size of the original was about 80*15-200*30μm. However, the crystal morphology remained rod-like. The transmittance profiles refered that re-crystallized particles gained remarkably transmittance enhancement compared to that of the suppplied one. In solvent diffusion process, components of three phases were changed to water / Benzyl alcohol / SDS＝10/10.5/5 (wt%). Sizes of particles tended to be larger from slow adding rate：10*6~30*10μm (50g/35mins)、15*2~40*4μm (100g/35mins)。
Partice sizes of pigment red 177 were reduced from 269.7nm to 201nm after processing with DMSO / AOT / Heptane microemulsion. For pigment green 36 in w/o microemulsions at four different temperatures (25℃、40℃、60℃、80℃), it was found that particles tended to aggregate as temperature increased. The results at 25℃ were listed below. Changes of particle sizes after 0、1、3、6 days of dispersion for each system are DMSO / AOT / Heptane：214.7、210.9、234.4、263.1(nm) and DMSO / AOT / Cyclohexane：261.6、281.5、279.2、296.4(nm) whereas sizes of the original pigment were 297.2、282.5、316.7、457.9(nm). These results have proved that the microemulsion method could efficiently make pigment particles dispersed. In addition, we tried to disperse pigment particles in microemulsions with variable surfactant concentrations. And similar transmittance results of pigment blue 15:6 were obtained in DMSO / AOT / Isooctane system (wt%：2/28/20、2/28/30). At 500nm wavelength, the transmittance was about 98.9% which is 20.0-20.2% raised from the original one (80.9%).
Subjects
Micronization
Microemulsions
Despersion
Type
thesis
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