Yoshinari Taguchi

Preparation of fine composite particles composed of inorganic solid powders and organic polymers by utilizing liquid-liquid dispersion

Abstract Composite particles composed of organic polymer and inorganic powder were prepared by two methods; suspension polymerization and drying-in-liquid method. The hydrophilic powders such as nickel, magnetite and indium oxide were added into the continuous water phase. Composite particles which were uniformly covered with these powders were prepared. It was investigated how the operating conditions, such as the size of solid powder, the amounts of powders added and the impeller speed, affected the characteristics of composite particles.

Preparation of titania/silica composite microspheres by sol–gel process in reverse suspension

Silica gel microspheres were prepared by sol-gel process of silicon tetraethoxide in reverse suspension. Subsequently, titanium tetra-2-propoxide solution was added to the system for producing titania gel. The composite microspheres prepared were analyzed with optical microscopy, electron probe microanalysis, and X-ray diffraction. Lowering the titanium alkoxide concentration in the continuous phase was effective to depress the agglomeration of fine titania particles. When the titanium alkoxide solution was divided into four parts and each aliquot was added separately, the covering state with titania became more uniform. The composite microspheres prepared were suspended in dye solution under ultraviolet irradiation and examined for the possibility of treating wastewater. The dye concentration rapidly decreased more than with a commercial titania powder, due to the effects of both photodegradation and adsorption.

Preparation of silica particles by sol-gel process in reverse suspension

Sol-gel process of silicon alkoxide was performed in reverse suspension to limit the sites of hydrolysis and dehydration-condensation of alkoxide to the inside of the dispersed droplets and to prepare silica particles of tens μm in diameter. Acetic acid aqueous solution was used as a dispersed phase, and hexane as a continuous phase. The dispersed phase was poured into the continuous phase, in which silicon alkoxide has dissolved, with stirring to form a reverse suspension. Silica particles of 67 μm in mean diameter were obtained by calcining the gel particles produced. Effects of pH of the dispersed phase and concentration of dispersion stabiliser on the characteristics of the silica particles were discussed. The formation mechanism of the gel particle was inferred with applying Janders model, which is often used to analyse solid phase reaction of particles.

Microencapsulation of Hydrophilic Solid Powder as a Fire Retardant by the Method of in situ Gelation in Droplets Using a Non-aqueous Solvent as the Continuous Phase

Hydrophilic, solid, powdery diammonium bitetrazole (BHT.2NH3) as a fire retardant was microencapsulated with epoxy resin by the method of in situ gelation in droplets to give water resistance. In this method, a non-aqueous solvent was adopted as the continuous phase instead of water to prevent the hydrophilic core material from leaking out. In the experiment, it was mainly the agitation speeds during preparation of droplets containing BHT.2NH3 and during the microencapsulation process, the gelation temperature, and the oil-soluble surfactant species that were varied. The content of core material could be increased by using a non-aqueous solvent instead of water phase. The content of core material increased with gelation temperature and independently of the agitation speeds during first droplet preparation and during the microencapsulating process. The leakage ratio increased with agitation speeds and decreased considerably with gelation temperature.

Preparation of Microcapsules Containing β-Carotene with Thermo Sensitive Curdlan by Utilizing Reverse Dispersion

We have tried to microencapsulate β-carotene with curdlan of a thermogelation type polysaccharide. Microcapsules were prepared by utilizing reverse dispersion, in which salada oil was the continuous phase (O’) and the curdlan water slurry (W) was the dispersed phase. β-carotene (O) as a core material was broken into fine oil droplets in the dispersed phase to form the (O/W) dispersion. The (O/W) dispersion was poured in the continuous phase (O’) and stirred to form the (O/W)/O’ dispersion at room temperature and then, temperature of the dispersion was raised to 80 °C to prepare curdlan-microcapusles containing β-carotene. In this microencapsulation process, the concentrations of curdlan and oil soluble surfactant and the impeller speed to form the (O/W)/O’ dispersion were mainly changed stepwise. We were able to prepare microcapsules by the microencapsulation method adopted here. The content of core material was increased with the curdlan concentration and decreased with the impeller speed and the oil soluble surfactant concentration. With the curdlan concentration, the drying rate of microcapsules was decreased and the retention ability for water was increased due to the stable preservation of β-carotene.

Preparation of Microcapsules Containing Camellia Oil with Heterocoagulation between Chitosan and Oleic Acid

It was tried to microencapsulate camellia oil using heterocoagulation between fatty acid dissolved in camellia oil and chitosan dissolved in the continuous water phase. Oleic acid as a fatty acid was dissolved in camellia oil in order to certainly form the microcapsule shell made from oleic acid and chitosan. The microcapsules were observed with optical microscope and characterized about the diameters, ζ-potential, FTIR analysis and adhesion feature on human hair. Microcapsules with the mean diameter in the range from ca. 1.5 μm to 4.5 μm could be prepared with the preparation method presented in this study. The oil droplets of camellia oil charged negatively to be -54.6 mV and the microcapsules charged positively to be 59.6 mV. The microcapsules adhered well on the negatively charged human hair and were kept stably before and after drying at room temperature for 24 h and blowing.

Preparation of Soft Microcapsules Containing Multiple Core Materials with Interfacial Dehydration Reaction Using the (W/O)/W Emulsion

Abstract The soft microcapsules containing eucalyptus oil, ubiquinone and the fine water droplets could be prepared with interfacial dehydration reaction between hydroxy methyl cellulose and tannic acid using the water-in-oil-in-water type multiple (W/O)/W emulsion. The diameters of the microcapsules and the content and the microencapsulation efficiency of the core materials were significantly affected by the revolution velocity (Nr1) to form the (W/O) emulsion and the revolution velocity (Nr2) to form the (W/O)/W emulsion and the lecithin concentration. The mean diameters of the inner water droplets and those of the microcapsules were proportional to Nr1−1.25 and Nr1−0.11 for the revolution velocity (Nr1), respectively. With increasing the revolution velocity (Nr1), the content and the microencapsulation efficiency of the inner water droplets increased, while those of the oil phase decreased. The mean diameters of the microcapsules were proportional to Nr2−1.1. The content and the microencapsulation efficiency of the inner water droplets and those of the oil phase decreased with the revolution velocity (Nr1) and increased with the lecithin concentration.

Preparation of Core-Shell Composite Particles Containing a Dye Powder by a Droplet Coalescence Method

It was attempted to prepare core-shell composite particles containing a hydrophilic dye powder by a droplet coalescence method using liquid-liquid dispersion. Core particles composed of dye powder and oleic acid have been forced to coalesce with styrene monomer droplets, and then suspension polymerization has been performed to form the polystyrene shell. In the experiment, the number and diameter of styrene monomer droplets were mainly changed stepwise to promote coalescence between the core particles and the monomer droplets and to control the shell thickness. It was found that the core shell composite particles could be prepared by increasing the monomer droplet number at the constant impeller speed, because the coalescence frequency between the monomer droplets and the core particles increased with the monomer droplet number at the constant impeller speed. Moreover, the diameter and shell thickness of the core shell composite particles increased with the diameter of monomer droplets.