In order to change the color of lithol rubine B (R-201) and to increase the chroma of its dispersion, we attempted to control the crystal form during the drying process in the recrystallization. Amorphous lithol rubine B was prepared for the first time, which was accomplished by freeze-drying or spray drying to yield thin films or microcapsulelike particles, respectively. These pigments dispersed in caster oil had the following features in comparison with commercially available pigments : (i) more reddish in color, (ii) higher chroma, and (iii) higher transparency. The reasons for the changes in color and the enhancement in the chroma were considered to be due to the amorphous state and thinness. It was found, however, that the pigment formed crystals with heating and/or during longterm storage to change its color. The stabilization in color was effected by the treatment with abietic acid derivatives, which are well-known inhibitors of crystallization.
The crystal change of cobalt phthalocyanine (Co-PC) in the presence of an organic solvent was studied to clarify the catalytic mechanism of Co-PC. β-Type Co-PC, which can be transformed into α type by the high-pressure hydrogen treatment, was not converted in the presence of an organic solvent up to the three 300-minute treatments. α-Type Co-PC, on the other hand, was converted into β immediately after the treatment with a solvent. The reaction converted benzene, which was used as the solvent for the Co-PC treatment, into cyclohexane, cyclohexene, cyclohexadiene, etc. Benzene hardly reacted in the absence of Co-PC under the same condition of the solvent treatment. β-Type Co-PC may also be transformed into α type even in an organic solvent under high-pressure hydrogen. However, the transformed α-type Co-PC could be converted rapidly to β type as a results of the reaction with solvent. Co-PC as a hydrogen carrier forms a hydrogen-transfer cycle.
The grafting of polymers onto carbon black by Friedel-Crafts reaction of acyl chloride-capped polymers with polycondensed aromatic rings of the surface was investigated. Acyl chloride-capped polymers (PPG-COCl) were prepared by the reaction of diol-type poly (propylene oxide) (PPG) with car-boxylic acid dichloride, such as succinyl dichloride, adipoyl dichloride, and phthaloyl dichloride. It was found that by the reaction of carbon black with PPG-COCl in the presence of AlCl3 at 60°C, PPG was successfully grafted onto carbon black surface. On the contrary, by the treatment of carbon black with PPG in the presence of AlCl3 and by the treatment with PPG-COCl in the absence of AlCl3, the grafting of PPG onto carbon black surface was rarely observed. Based on the above results, it was concluded that the grafting of PPG onto the carbon black surface proceeded by Friedel-Crafts reaction of PPG-COCl with polycondensed aromatic rings of carbon black surface. The percentage of grafting increased with increasing molecular weight of PPG-COCl, but the number of grafted PPG chain decreased. The effects of reaction temperature and catalyst on the grafting reaction were also, discussed. Furthermore, PPG-graf ted carbon black gave a stable colloidal dispersion in a good solo-vent for PPG.