Journal of the Society of Powder Technology, Japan

The Coating Surface and Agglomeration of Seed Particles in a Fluidized Bed Coater

Hiroyuki KAGE, Toru TAKAHASHI, Takayuki YOSHIDA, Hironao OGURA, Yoshiz ...

1998 Volume 35 Issue 1 Pages 4-11
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.4

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Glass beads were coated in a fluidized bed by atomizing the suspension of nylon or silica fine powder. Polyvinyl alcohol (PVA) was used as a binder. The influences of the weight ratio of fine powder to binder in the suspension and index R, which quantitatively evaluates the drying condition in a fluidized bed on the coating efficiency, on the agglomeration among the core particles and on the coated layer surface were investigated. When the index R became high and the weight ratio of powder to binder decreased, the core particles easily agglomerated. Once agglomeration occurred, both the coating efficiency and the circularity, which evaluates the smoothness of coated surface, became worse. Furthermore, the addition of the surfactant in the suspension made the circularity high and inhibited the agglomeration. In contrast, the hydrophobic surface of the core material made the coating efficiency at the early coating stage and circularity low, and it encouraged the agglomeration.

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An Experimental Study on the Grinding Rate Constant of a Ball Mill

The Effects of Feed Size and Ball Diameter

Yoshiteru KANDA, Kiichi SIMODAIRA, Naoya KOTAKE, Yasushi ABE

1998 Volume 35 Issue 1 Pages 12-17
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.12

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The grinding rate constant is one of the important factors needed to estimate or evaluate a grinding process. It has been found that the decreasing rate of the feed size was described by a first-order equation in the initial grinding stage of various mills.
In this study, grinding tests were carried out on silica glass using a ball mill, and the grinding rate constant of feed size decrease were measured. The effects of the ball diameter and the feed size on the rate constant were investigated when the mass of balls, the mass of feed and the rotational speed of the mill were constant.
As the result of the tests, the grinding rate constant could be expressed by modifying the equation which was proposed by Snow as the function of ball diameter and feed size.

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The Influences of Operating Parameters on the Recovery of Coated Single-Core Particles by the Spray Drying of Suspensions

Noriyuki YAMADA, Eiichi ABE

1998 Volume 35 Issue 1 Pages 18-24
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.18

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The coating of fine particle was carried out by spray drying with a pneumatic nozzle. The raw powders that served as the core particles used in the experiments were particles with a narrow size distribution for polishing use. The coating material was ethyl cellulose dissolved in an ethanol and water mixture. The operating parameters were the composition of the suspensions, the concentration of ethyl cellulose and the core particle sizes. The recovery of single-core particles produced by spray drying was able to be formulated as a function of the operating parameters. The factor that most significantly influenced the recovery of single-core particles was particle size. The smaller the size, the less the single-core particles obtained. The thickness of the liquid film which adhered to the surface of a particle was estimated to be around 2.4μm.

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The Adsorption Behavior of Dispersant Molecules and Rheological Properties of Highly Concentrated Alumina Slurries

Hidero UNUMA, Bevon-Hwan RYU, Isao HATANO, Minoru TAKAHASHI

1998 Volume 35 Issue 1 Pages 25-30
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.25

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The adsorption of polyacrylate ammonium dispersant on alumina particles was analyzed for alumina slurries with various solid loadings up to 57.5vol% by FT-IR spectroscopy, with which the rheological properties were correlated. For alumina slurries of pH around 9.3, unadsorbed dispersant molecules always existed in the dispersion media even when the amount of the dispersant was insufficient for optimum dispersion. When solid loading was higher than a critical value (50vol%, in the present case), the adsorption of dispersant was suppressed with increasing solid loading. Correspondingly, the agglomeration of the slurries became pronounced. At the critical solid loading, the mean interparticle distance was estimated to be close to the length of the dispersant molecule. It was assumed that, in such highly concentrated slurries, the adsorption of the dispersant molecules should be suppressed.

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In-situ Evaluation of Properties of Solid- Liquid Interface by Atomic Force Microscope

Ko HIGASHITANI, Yoichi KANDA

1998 Volume 35 Issue 1 Pages 31-39
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.31

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[title in Japanese]

Jun YOSHIDA

1998 Volume 35 Issue 1 Pages 59-60
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.59

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[title in Japanese]

Hisao SUZUKI, Junichi TAKAHASHI

1998 Volume 35 Issue 1 Pages 61-65
Published: January 10, 1998
Released on J-STAGE: April 30, 2010

DOIhttps://doi.org/10.4164/sptj.35.61

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