Vibration Rod Mill Research Articles

Prediction of power of a vibration rod mill during cellulose decrystallization processing by DEM

The crystallinity index of cellulose decrystallized with a vibration rod mill was well correlated with input energy of the vibration rod mill. In order to predict the energy, rod behavior was simulated by discrete element method (DEM).Decrystallization of cellulose was performed using a vibration rod mill to increase the reactivity. The decrystallization speed increased with an increase in the number of rods and the crystallinity index of cellulose after pulverization can be uniquely identified by the input energy [kWh/kg], which is actual power times pulverization time divided by cellulose mass charged into the vibration rod mill. Therefore, the actual power of the vibration rod mill was calculated using DEM simulation, wherein rods were constructed by connecting spherical particles using the multi-sphere method. The coefficients of friction and restitution were determined based on the movement of the rod in the mill cylinder from the experiments. The power calculated agrees with the actual power. This study suggests that the power of the vibration rod mill can be predicted using DEM and that the crystallinity index can be predicted without experimentation.

Preparation of acetylated wood meal and polypropylene composites II: mechanical properties and dimensional stability of the composites

Acetylated wood meals of Sugi (Cryptomeria japonica D.Don) wood were prepared by mechanochemical processing using a high-speed vibration rod mill. Weight percent gain (WPG) of the acetylated wood meals ranged from 7.0 to 35.5 %. Wood–plastic composites (WPCs) containing 50 % acetylated woods were produced by an injection molding technique. The polymer matrix used was polypropylene homopolymer. Maleic anhydride-grafted polypropylene (MAPP) was also used as a compatibilizing agent. The mechanical properties of WPCs in bending and tensile tests were independent of WPG of acetylated wood meals, and the test values for WPCs containing acetylated wood meals were lower than that of unmodified wood meal. The use of MAPP increased bending and tensile strength, but no effect on bending modulus was found. An increase in WPG significantly decreased water absorbability and thickness swelling of WPCs as measured by dimensional stability tests. These results demonstrated that mechanochemical processing is a promising technique for preparing WPC material with improved dimensional stability. The future challenge is to inhibit the decreases in mechanical properties of WPCs containing acetylated wood meals.

Preparation of acetylated wood meal and polypropylene composites I: acetylation of wood meal by mechanochemical processing and its characteristics

Wood meals of Sugi (Cryptomeria japonica D.Don) passing 2.0 mm and retained on 1.0 mm mesh screens were milled along with acetic anhydride (AA) and pyridine as a catalyst in a high-speed vibration rod mill at ambient temperature. The weight percent gain (WPG) of the chemically modified wood was calculated based on the yield after washing with deionized water. The effects of amounts of AA and catalyst added, pulverization time, and saponification of the acetylated wood on WPG were examined. In addition, FT-IR analysis, and water vapor adsorption and desorption tests were performed as functions of the WPG. Increases in WPG, the acetyl contents of the acetylated wood after saponification, changes in the FT-IR spectra after pulverization, and the water vapor sorption isotherms showed that the one-step acetylation systematically modified the hydroxyl groups of the wood into acetyl groups. Up to 38 % WPG was obtained at 100 phr AA and 15 phr catalyst, and 120 min pulverization. Pulverization time and the amounts of AA and catalyst added to the wood meals could be adjusted to obtain acetylated wood meal with the desired WPG. These demonstrated that the mechanochemical acetylation is a method to prepare acetylated wood meals with high WPG at less reaction time and required AA addition.

Mechanism of Nanoparticle Formation from Ternary Coground Phenytoin and Its Derivatives

The mechanism of drug nanoparticle formation of phenytoin (DPH) and its derivatives monomethylphenytoin (MDPH) and dimethylphenytoin (DMDPH) was investigated. The drug, polyvinylpyrrolidone K17 (PVP), and sodium dodecyl sulfate were coground to obtain the ground mixture (GM). The DPH GM was amorphous; however, MDPH and DMDPH GMs contained drug crystals. Spectral changes in infrared and (13)C solid-state nuclear magnetic resonance were observed in the DPH GM, partially observed in the MDPH GM, and hardly observed in the DMDPH GM. Mean particle sizes of the DPH, MDPH, and DMDPH GM nanosuspension were almost the same; however, stability after storage differed in the order of DPH > MDPH > DMDPH. The intermolecular interaction between the drug and PVP reflected not only the crystallinity of the drug in the GM but also the stability of the GM suspension. The size and stiffness of drug nanoparticles were evaluated using atomic force microscopy. Crystallization of the amorphous GM and agglomeration of the primary nanocrystals were observed in the DPH GM suspension. In contrast, primary nanocrystals were observed in the DMDPH GM suspension. The size of the drug nanocrystals formed from the different molecular states of the drug in the GM reflects the agglomerated states in water and stability.

Formation mechanism of a new carbamazepine/malonic acid cocrystal polymorph

A new 2/1 carbamazepine (CBZ)/malonic acid (MA) cocrystal polymorph form C was formed using a vibrational rod mill, whereas the known cocrystal polymorph form A was prepared using a ball mill. IR measurements showed that the interaction between CBZ and MA in cocrystal form C was formed by amide–carboxylic acid heterosynthons, similar to that in cocrystal form A. However, NMR results showed that the molecular states of CBZ at the dibenzazepine ring appeared to be different, which could be due to variation in either the conjugation of the aromatic rings or the π–π interaction of CBZ. Factors affecting the formation of cocrystal polymorphs, such as heat and force, were investigated to clarify the formation mechanism.

Enhanced skin permeation of piroxicam and pranoprofen induced from nanoparticles dispersed in propylene glycol aqueous solution

The effects of water-soluble polymers on nanoparticle formation of piroxicam and pranoprofen were investigated. We also studied the effects of propylene glycol (PG) concentration in PG aqueous solution on skin permeation of the drugs from nanoparticles. Physical mixtures (PMs) of the drug, hydroxypropylmethylcellulose (HPMC), and sodium dodecyl sulfate (SDS) (weight ratio, 1:3:1) were ground for 90 min in a vibrational rod mill to prepare ground mixtures (GMs). The particle sizes of the GM suspensions in distilled water were 76 nm for piroxicam and 146 nm for pranoprofen, respectively. It was found that the permeation of piroxicam and pranoprofen through hairless mouse skin was significantly increased when the ternary GMs were suspended in PG aqueous solution; however, no enhanced permeation was observed with drug/HPMC binary GMs. Because the piroxicam/SDS binary GM caused skin damage, a ternary GM was critical for increasing the skin permeation of poorly water-soluble drugs. The skin permeation of piroxicam and pranoprofen could be attributed to their supersaturation in suspension due to nanoparticle formation. The skin permeation of piroxicam from the GM suspension was independent of PG concentration in PG aqueous solution, but that of pranoprofen increased with PG concentration in PG aqueous solution. This difference can be attributed to the different solubilities of piroxicam and pranoprofen in PG aqueous solution.

Chemical Property of Ground Calcium Carbonate as Carbon Dioxide Absorbent

Commercial sedimentation CaCO3 was ground by a vibration rod mill to investigate the physicochemical properties of mechanically activated CaCO3.When the CaCO3of the calcite structure was ground, the intensities of the crystal facesof calcite was decreased by distortions and so on, and the aragonite appeared as the grinding proceeded. The formed aragonite was transformed to the calcite when the sample was heated at 773K for3.6 ks. The dissociation pressure of CO2 of the ground CaCO3was larger than that of the non-ground CaCO3.The enthalpy; entropy and specific heat of change of the dissociation reaction were obtained. At high temperature, the emission rate of the ground CaCO3 was slightly larger than that of the non-ground CaCO3. At room temerature, the CaCO3 adsorbs CO2, and it desorbs the adsorbed CO2. The amount of adsorbed CO2 on the ground CaCO3 was larger than that of the non-ground CaCO3.

Micronization of Dihydroartemisinin by Rapid Expansion of Supercritical Solutions

The purpose of this study was to prepare fine particles of antimalarial drug dihydroartemisinin (DHA) by rapid expansion of supercritical solutions (RESS) using carbon dioxide as supercritical fluid. The mechanical grinding by jet mill and additional vibration rod mill also was performed as a comparative method. In the RESS process, drug particles were prepared by varying processing conditions, including extraction condition, pre-expansion condition, nozzle diameter, nozzle temperature, and collecting distance. Particle size and morphology and physicochemical characteristics of the drug particles were investigated. The RESS process could produce the smaller drug particles (about 1–2 μm) when compared to mechanical grinding method (about 7 μm). All RESS processing parameters had an effect on size and morphology of drug particles. The particle size of drug was related to the solubility of drug in supercritical CO2 at each processing condition. The fine particles of DHA (about 1 μm) with narrow size distribution could be obtained at extraction pressure of 18 MPa and extraction temperature of 32°C, which was closed to the critical temperature of supercritical CO2 whereas broad size distribution was obtained at extraction temperature of 60°C. Powder X-ray diffraction study indicated that the RESS-processed particles were in crystalline form. The results revealed that RESS process is applicable for micronization of DHA.

Formation mechanism of colloidal nanoparticles obtained from probucol/PVP/SDS ternary ground mixture

The purpose of this study was to investigate the formation mechanism of colloidal nanoparticles after dispersion of probucol/polyvinylpyrrolidone (PVP)/sodium dodecyl sulphate (SDS) ternary ground mixture (GM) into water. Probucol, PVP and SDS were mixed at a weight ratio of 1:3:1 and ground for 30 min with a vibrational rod mill. The morphology and physicochemical properties were investigated through high resolution scanning electron microscopy (SEM), environmental SEM, dynamic light scattering, 13C NMR and zeta potential measurements. SEM images confirmed the presence of 20 nm size primary particles in the GM powder of probucol/PVP K17/SDS. Spherical nanoparticles with a size of around 100 nm, formed after dispersion of the GM into water, suggested an agglomeration of the primary particles. A further agglomeration of around 160 nm was observed with the stability experiment. Zeta potential and particle size measurements using latex beads revealed that PVPK 17/SDS complex was adsorbed on the probucol particle surface forming a layered structure. A similar agglomeration behavior was observed using the GM of probucol/PVP K12/SDS, though the molecular state of the PVPK 12/SDS complex at the particle surface was different from that of the PVPK 17/SDS complex. 13C NMR results suggested that intermolecular interactions between PVP K12 and SDS did not reach the same level as the interactions between PVP K17 and SDS. This study proposed a formation mechanism of colloidal nanoparticles.

石灰石の乾式超微粉砕における液体添加物の助剤効果と添加物分子の挙動

The effect of liquid additives such as alcohol and glycol on the ultrafine grinding of limestone was investigated by using a vibration rod mill. Liquid additives used in the present work were three alcohols and two glycols with different alkyl groups. The experiments were carried out by a batch operation, and the change in specific surface area of limestone with grinding time was measured by BET adsorption method. The behavior of methanol molecules added as a additive was traced by monitoring the temperature and pressure in the grinding pot during grinding. The results showed that the alcohols and glycols promote ultrafine grinding of limestone, and that the maximum specific surface area of limestone obtained with additives is proportional to the amount of additive. The stepwise addition of a small amount of additive was more effective rather than adding the whole amount at once in increasing the grinding rate of limestone. It was also found that the degradation of crystal structure of limestone was controlled by the addition of alcohol. The grinding status of limestone could be traced by monitoring the temperature in the grinding pot, and the measurement of pressure change in the grinding pot revealed that the additive molecules are chemisorbed on the fresh surface of limestone created by the grinding.

Amorphous ultrafine particle preparation for improvement of bioavailability of insoluble drugs: grinding characteristics of fine grinding mills

This paper describes the preparation of ultrafine particle of insoluble drugs in water and the improvement of physico-chemical properties by using three types of fine grinding mills such as a planetary ball mill, a vibration rod mill, and a jet mill. Ursodeoxycholic acid (UDCA) was used as the model drug of insoluble drug. The samples ground by three mills were characterized by particle size distribution measurement, apparent solubility measurement, powder X-ray diffraction (PXRD), and in vivo test of a hindrance effect of reactive oxygen species (ROS) generation. The ground sample of UDCA with the vibration rod mill among the three grinding mills showed a high amorphous state and a high apparent solubility than other two mills, and the formulation prepared with ultrafine particle of UDCA decreased the reactive oxygen species generation and the lipid peroxidation in CCl 4-induced oxidative stress mice.

Formation and stability of drug nanoparticles obtained from drug/PVP/SDS ternary ground mixture

The purpose of this study was to investigate the stability and the formation mechanism of drug nanoparticles obtained from a ternary system consisting of poorly water-soluble drug, polyvinylpyrrolidone (PVP), and sodium dodecyl sulfate (SDS). The physical state of drug nanoparticles was investigated by powder X-ray diffraction and zeta potential measurements. Poorly water-soluble drug, PVP K17 and SDS were mixed at a weight ratio of 1:3:1 and ground for 30 min by vibrational rod mill. Most of the poorly water-soluble drugs used in this study provided the nano- particle formation in the submicron region after the ternary ground mixtures (GMs) were dispersed into distilled water. Stability and mechanism of drug nanoparticle formation were investigated by focusing on phenytoin, probucol and griseofulvin. The drug nanoparticle formation was also observed when the ternary GMs were dispersed in the dissolution media. The mean particle size of the dispersed particles was still less than 250 nm after storage at 25°C for one month, indicating the long-term stability of drug nanoparticles. The quantitative determination of drug content demonstrated that more than 93% of the drug was recovered as fine particles smaller than 0.8 ^m from the ternary GMs, whereas the nanoparticles were hardly gained from binary GMs, drug with PVP K17 or SDS. Powder X-ray diffraction analysis for the dispersed particles accumulated by ultracentrifugation indicated that the dispersed particles existed as fine crystals. The zeta potential measurement revealed that the obtained nanoparticles were stable in aqueous media because the particle agglomeration was effectively inhibited by the adsorption of both PVP and SDS onto the particle surface.

アルミナの超微粉砕における液体添加物の助剤効果とアルミナ粉体の挙動

The effect of liquid additives of grinding aid on the ultrafine grinding of alumina was studied by using a vibration rod mill. Liquid additives studied were five alcohols and two glycols with different alkyl groups. Experiments were carried out by batch operation, and the changes in specific surface area of products with grinding were measured by BET adsorption method. The behavior of alumina powder during grinding was also investigated by monitoring the temprature change of the grinding vessel. The results showed that alcohols and glycols had a significant effect on the ultrafine grinding of alumina as a grinding aid. The maximum specific surface area of alumina obtained with an additive was found to increase proportionally with the amount of additive. The thermal analysis of ground products suggested that three molecular layer of the additive molecules existed on the product surface when the specific surface area reached the maximum value. It was found that the monitoring of the temperature change of grinding vessel would be useful in understanding the grinding status.

Studies of rapidly disintegrating tablets in the oral cavity using co-ground mixtures of mannitol with crospovidone.

We attempted the development of rapid oral disintegration tablets by direct compression using co-ground mixture of D-mannitol and crospovidone. The co-ground mixture was prepared with a vibration rod mill. The tablets were formed by compression using a single punch-tableting machine after addition of the co-ground mixture to non-ground D-mannitol, crospovidone and magnesium stearate. Regarding the properties of tablets, hardness and the time of disintegration were measured. The particle diameter and specific surface area of the co-ground mixture were measured. The tablets manufactured from a physical mixture of 30% (w/w) co-ground mixture of D-mannitol and crospovidone (mixed ratio 9 :1) with 65.5% (w/w) of non-ground mannitol, 4% (w/w) of crospovidone, and 0.5% (w/w) of magnesium stearate had good properties for rapidly disintegrating tablets in the oral cavity. They showed the hardness of 4.9 kg and disintegration time of 33 s. We found that adding co-ground mixture of D-mannitol and crospovidone is useful in enhancing hardness of the tablets that could not be achieved by addition of their individually ground mixture. The improvement in the hardness of the tablets was also observed when other saccharides and disintegrants were used. This method was proved to be applicable in the manufacture of tables of ascorbic acid, a water-soluble drug and nifedipine, a slightly water soluble drug; and the dissolution rate of nifedipine from the tablets in water was remarkably improved. The particle sizes of D-mannitol in the co-ground mixture were smaller than that of the individually ground mixture, resulting in a larger specific surface area of the co-ground mixture than that of the individually ground mixture. Therefore, it was presumed that crospovidone acted as a grinding assistant for D-mannitol in the co-grinding process, enhancing the hardness of tablets by increasing the contact area among powder particles.

A Nifedipine Coground Mixture with Sodium Deoxycholate. II. Dissolution Characteristics and Stability

Nifedipine is a poorly water soluble drug that demonstrates low bioavailability. In a previous study, a coground mixture of nifedipine with sodium deoxycholate (DCNa), a bile salt, immediately produced colloidal particles when dispersed in water. In this study, the effect of the weight fraction of DCNa, grinding time, dissolution media, and storage conditions on colloidal particle formation in solution was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction. A laser diffraction particle size analyzer was used to determine the particle size distribution curve in water. The size of particles formed in solution decreased with an increase in the weight fraction of DCNa and grinding time. A nifedipine-DCNa (1 : 2 w/w) mixture coground for 30 min was used in the experiments. Colloidal particle formation from the coground mixture was also observed in dissolution media of water and a pH 6.8 buffer solution at 37°C. Most precipitates passed through a filter with a pore size of 0.8 μm, but the particle size distribution in water was different from that in the pH 6.8 buffer solution. DCNa exhibited not only micellar solubilization for drug crystals, but also a retarding effect on drug crystal growth in a supersaturated solution. The latter effect could serve to form colloidal particles in solution. When stored under 75% relative humidity at 40°C for 1 month, the amorphous coground mixture crystallized, and the particle size in water markedly increased. Therefore, the weight fraction of DCNa, grinding time, dissolution media, and humidity during storage influence the dissolution characteristics of nifedipine from a coground mixture.

A Nifedipine Coground Mixture with Sodium Deoxycholate. I. Colloidal Particle Formation and Solid-State Analysis

Sodium deoxycholate (DCNa) is a bile salt that forms multimolecular inclusion compounds with a variety of organic substances. In this study, complex formulation of DCNa with nifedipine, a poorly water soluble drug, by grinding was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. A laser diffraction particle size analyzer was also used to determine the particle size distribution curve in solution. When a nifedipine-DCNa (1:2 w/w) mixture coground for 30 min was dispersed into water and a pH 6.8 buffer solution, a semitransparent colloidal solution occurred immediately; 90% of the total particles formed in solution had a diameter less than 600 nm. Both powder X-ray diffraction peaks and DSC endothermic peak of nifedipine crystals were not found for the coground mixture, whereas a new exothermic peak was observed on DSC thermograms. The magnitude of this exothermic peak depended on the weight fraction of DCNa and the grinding time, indicating that nifedipine crystals changed into an amorphous state by complex formation with DCNa during the grinding process. In the FTIR spectrum of the coground mixture, the peaks of aromatic CH out-of-plane bend and dihydropyridine NH stretch of nifedipine were considerably weakened, suggesting that van der Waals interaction may be present between the drug and DCNa molecules. From these results, it is clear that the cogrinding method with DCNa is very useful for the formation of amorphous nifedipine in the solid state and the production of colloidal particles of the drug in solution.

The effect of liquid additives on dry ultrafine grinding of quartz

The dry ultrafine grinding of quartz with liquid additives was carried out using a vibration rod mill with a laboratory scale. Liquid additives used were mainly seven alcohols and three glycols with different alkyl groups. All of the experiments were carried out by batch operation, and the variations of specific surface areas of products with grinding time were measured by BET adsorption method. The results showed that alcohol and glycol additives were satisfactorily effective for the ultrafine grinding of quartz. The maximum specific surface area of quartz obtained with an additive was found to increase in proportion to the amount of the additive. The additive molecules of multimolecular layers were supposed to adsorb on the quartz surface when the specific surface area reached the maximum value. The principal effect of additives in ultrafine grinding is considered to be the increase in flowability and the control of reagglomeration of quartz powder due to the alkoxylation of hydroxyl groups on the quartz surface.

Effect of crystallinity of microcrystalline cellulose on the compactability and dissolution of tablets

Microcrystalline cellulose (MCC) was pulverized with a vibrational rod mill. The degree of crystallinity of MCC decreased from 65.5 to 12.1% with pulverization time due to mechanochemical effect. Pulverized MCCs were compressed at 155.6 MPa using a compression test apparatus, and the two parameters relating to compactability, the B value and yield pressure, were calculated using a Heckel plot. These values were lowered as the degree of crystallinity of MCC became smaller. These results suggest that the crystal region and the amorphous region in MCC particles may be mainly fractured and deformed plastically during compression, respectively. Then the dissolution test was performed for the acetaminophen-MCC (10:90) tablets. Dissolution profiles showed an interesting phenomenon, namely, the dissolution rate of acetaminophen from MCC tablet decreased when the degree of crystallinity of MCC was in the range from 65.5 to 37.6%, however, it increased markedly when the degree of crystallinity of MCC was in the range from 25.8 to 12.1%. The amount of water absorbed into tablets changed in accord with the dissolution rates of acetaminophen from tablets. The dissolution data indicate that drug release can be modified by changing the degree of crystallinity of MCC.

Effect of Crystallinity of Microcrystalline Cellulose on Granulation in High-shear Mixer.

Granulation was carried out using binary mixtures of microcrystalline cellulose (MCC) and cornstarch (CS); water was used as granulating liquid. The effect of crystallinity of MCC on granulation was examined using MCC pulverized by a jet mill (J-MCC) and a vibrational rod mill (R-MCC). Crystallinity of J-MCC was nearly equal to that of intact MCC (I-MCC), but that of R-MCC was remarkably low due to the mechanochemical effect. The growth rate of granules with R-MCC was greater than those with I-MCC and J-MCC; the latter two had a grnule having a core (MCC and CS) around which CS was layered. R-MCC provided granules in which CS and abraded MCC were homogeneously mixed. In addition, R-MCC remarkably decreased the difference in drug content among the size fractions of granules compared with I-MCC. These results suggest that the decrease in crystallinity of MCC may increase the tendency of its abrasion by shear force of impeller, because of an increase of the fragile amorphous region swollen by added water; this, in turn, results in a difference in the growth mechanism and in a greater growth rate.