Journal of the Society of Powder Technology, Japan
Online ISSN : 1883-7239
Print ISSN : 0386-6157
ISSN-L : 0386-6157
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Volume 35, Issue 9
Displaying 1-9 of 9 articles from this issue
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  • [title in Japanese]
    Masatoshi CHIKAZAWA
    1998 Volume 35 Issue 9 Pages 629
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.629
    JOURNAL FREE ACCESS
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  • Separation Characteristics of a Wet Shape Separator Developed for Fine Particles
    Kenichi YAMAMOTO, Naoki SHIMIZU, Masunori SUGIMOTO, Yoko MATSUOKA
    1998 Volume 35 Issue 9 Pages 630-638
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.630
    JOURNAL FREE ACCESS
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    In order to investigate separation performance of a wet shape separator developed for fine particles, experiments were carried out using binary solid mixtures of about 50-250μm particles with different shapes. As a result, it was found that; (1) the separtion mechanism of separator was based on the difference in static rolling frictional characteristics between spherical and non-spherical particles on a rotating conical disk in liquid, (2) continuous shape separations could be achieved by sweeping particles on the rotating conical disk by liquid jet, (3) separation efficiencies depended on various experimental conditions, such as surface roughness of disk material, particle size, flow rate for sweeping particles, surface inclination angle and rotational speed of conical disk, (4) even mixture of fine 50μm-sized particles could be effectively separated under appropriate operating conditions.
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  • Production of Powder with Water-hardening Property from Fly-ash by a Mechanochemical Method
    Guomin MI, Fumio SAITO, Yoshio WASEDA, Takeshi NARITA
    1998 Volume 35 Issue 9 Pages 639-643
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.639
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    Mechanochemical treatment has been applied to a mixture of fly-ash and CaO powder under dry atmospheric condition using a planetary ball mill to produce powder with water-hardening property. An increase in grinding time appears to induce amorphisation of both master compounds. Prolonged grinding for more than 30 minutes enables the production of powders with water-hardening property. The water-hardening property found in this work is due to the formation of hydrated calcium silicate in the mixture, and such feature becomes more significant as the grinding progresses.
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  • Effects of CF4 Plasma Surface Treatment on Charging Characteristics of Polyvinylchloride (PVC) Powder
    Shintaro YAMADA, Fujio KANEKO, Motoaki KOMATA, Manabu TAKEUCHI
    1998 Volume 35 Issue 9 Pages 644-648
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.644
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    Plasma surface treatment was carried out by using CF4 gas for polyvinylchloride (PVC) powder to improve its charge retention ability. An rf CF4 plasma was generated in a flask using a pair of external electrodes connected to an rf generator of 13.56MHz. The plasma treatment was performed at the rf power of 40W and the gas pressure of 27Pa for 2h. It was confirmed that the plasma treatment enhanced the charge retention ability of the PVC powder. The plasma treatment shifted the charging tendency of the PVC powder in negative direction. The plasma treatment also improved the hydrophobicity, fluidity and thermal stability of the PVC powder.
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  • Specific Surface Area Measurement by Air Permeability with Consideration of Molecular Flow Effect
    Application of Rigden-type Permeability Equation
    Akira SUGANUMA, Yu MATSUMOTO, Egure MURATA, Toshitaka HAMADA
    1998 Volume 35 Issue 9 Pages 649-654
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.649
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    Since gas permeation through a powder bed is affected by molecular flow, applicability of the Kozeny-Carman equation neglecting this effect is limited to powders coarser than about 10μm. ΦB=ΦV+δΦM is a general expression of some permeability equations for finer powders, where ΦB denotes the permeability of a bed, ΦV the term of viscous flow and ΦM the term of molecular flow. δ is the constant for adjusting molecular flow effect. It was more than 40 years ago that δ=0.515 was proposed by Rigden, 0.97 by Lea & Nurse and 1.125 by Carman. Such a big discrepancy of δ is one of the reasons why the Kozeny-Carman equation is still in use. δ=0.82 was proposed as a reasonable value through the least squares analysis of Rigden's data and reference of the Knudsen's equation of capillary permeation. Using δ=0.82, more reasonable measurement of powders down to about 1μm may be possible.
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  • Particle Shape Control by Rounding Irregular Shaped Particles
    Effects of Particle Shapes on Fluidity of Pulverized Coal in CWM and Fly-ash Particles
    Tetsuo ONO, Yoshiyuki YAMASAKI
    1998 Volume 35 Issue 9 Pages 655-661
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.655
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    The shape of particles affects the flow resistance of slurry such as CWM (Coal Water Mixture) and cement slurry. If the particles are rounded, the slurry can maintain good fluidity due to a decrease in flow resistance.
    In this study, effect on fluidity of rounding irregular shaped particles having sharp edges is investigated. The particles are fed into a gap between two rotary disks rotating at different speeds. Mutual rubbing of particles scrapes the sharp edges and makes them round in shape. The method is applicable to the production of high-density CWM consisting of ultrafine particles. Furthermore, the method is also suitable for producing rounded fly-ash particles.
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  • Effect of Punch Velocity on the Compressibility and Stress Relaxation of Particles and Granules
    Kazumi DANJO, Akinori HIRAMATSU, Akinobu OTSUKA
    1998 Volume 35 Issue 9 Pages 662-670
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.662
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    Effect of punch velocity on compaction properties of particles and granules has been studied through compressibility, stress relaxation and elastic recovery. The compressibility of powders was evaluated by the modified Kawakita equation (K). The relationship between compression stress (P) and reciprocal of porosity (1/ε) showed an inflection point. Denoting the slope of low compression stress in the stage of densification by powder slippage and rearrangement by K1, and K2 the slope of high compression stress in the stage of elastic, plastic deformation and brittle fracture of particles and granules, the values of K1 and K2 decreased with increasing punch velocity. The diametral tensile strength had a tendency to decrease with decreasing K2, while stress relaxation increased with increasing punch velocity. In particular, constant a and b values in a cellulose system (microcrystalline cellulose) were greater than those in a non-cellulose system (α and β lactoses). As found in the relationship between constant a, b and constant K2, materials which undergo plastic deformation and fragmentation have high stress relaxation. It was also found that elastic recovery ratios of tablets increased with increasing punch velocity. Therefore punch velocity affects both the stress relaxation and elastic recovery ratio of tablets.
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  • Preparation of Spherically Granulated Crystals of Waxy Drug (Tocopherol Nicotinate) for Direct Tableting by Spherical Crystallization Technique
    Hiromitsu YAMAMOTO, Yasuyo SAKAI, Tomoaki HINO, Hirofumi TAKEUCHI, Yos ...
    1998 Volume 35 Issue 9 Pages 671-674
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.671
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    Spherically microagglomerated crystals of waxy drug (tocopherol nicotinate) for direct tableting were successfully prepared by a spherical crystallization technique. The micromeritic properties of the original tocopherol nicotinate crystals, such as flowability, packability, and mixing characteristics with excipients were drastically improved for tableting. The surface-modified agglomerated crystals with deposition of colloidal silica reduced sticking (caking) properties under loading and exudation of drug from agglomerated crystals under compression. The agglomerated crystals provided acceptable tablets with easily disintegrating and releasing functions by compressing with a suitable additives.
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  • [title in Japanese]
    [in Japanese]
    1998 Volume 35 Issue 9 Pages 675-684
    Published: September 10, 1998
    Released on J-STAGE: April 30, 2010
    DOIhttps://doi.org/10.4164/sptj.35.675
    JOURNAL FREE ACCESS
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