Masataka Tanigaki

Quality control of polymer production processes

For the polymer production industries, the competitive edge will come from the technology that excels in controlling the polymer properties in a consistent way over the entire plant and in maximizing the production performance while keeping safety regulations. Based on the experience in applying advanced process control and scheduling schemes to industrial polyolefin polymerization plants, the state of the art in quality control systems for providing the polymer production plant with an enlarged capacity for product discrimination and flexibility is reviewed. On-line soft-sensing and optimal grade changeover control problems are the main focus of this paper. A quality control system for polymer production plants, which integrates optimal control with on-line sensing and scheduling techniques, is discussed making reference to an application of a prototype system to an industrial plant. # 2000 IFAC. Published by Elsevier Science Ltd. All rights reserved.

Polymeric foaming simulation for extrusion processes

A numerical simulation for polymeric foaming extrusion processes was conducted. Combining classical nucleation rate and bubble growth models with a non-Newtonian fluid model of a flow, a simultaneous bubble nucleation and growth behavior in a flow field was simulated. Simulation results were compared with the experimental data obtained by visual observations at a foaming extruder, where a polypropylene resin was physically foamed. The effects of physical parameters in foaming model on bubble size and number density calculation were intensively examined by sensitivity analysis.

Laser flash method for measuring thermal conductivity of liquids—application to low thermal conductivity liquids

A laser flash method developed for the measurement of thermal conductivity of solids was applied to liquids of low thermal conductivity. The sample liquid was sandwiched in between a small thin metal disk and a sample holder. When the laser beam is absorbed in the front surface of the metal disk, the temperature of the disk quickly rises about 2 K and heat then flows downwards through the sample liquid as one-dimensional heat flow. The thermal conductivity of liquid can be obtained from the temperature fall of the disk without employing any reference materials and also without measuring the thickness of the sample liquid layer. Thermal conductivities of water and toluene near room temperature were measured by this method with a mean deviation of 2.6%. This laser flash method may be applied to the measurement of the thermal conductivity of liquids such as molten salts at elevated temperatures.

Preparation of nanoporous MgO using gel as structure-direct template

MgO with various nanoscaled pore diameters were formed from magnesium nitrate adsorbed into the gel templates that are synthesized from hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) where the EGDMA worked as the cross-linker. The effects of molar ratio [HEMA]/[EGDMA] in the gel template on the porous structure of MgO formed in the template were investigated. The results indicated that the pore diameter of MgO could be varied by the [HEMA]/[EGDMA] molar ratio which directly affects the templating structure of gel. The smaller pore size and distribution were obtained with the increased molar ratio. The mechanism of the reaction was simply speculated.

Synthesis of submillimeter-thick films of surfactant templated mesoporous silica

Abstract Submillimeter-thick mesoporous silica films using tetraethoxysilane (TEOS) as a silica source and the hexagonal mesophase of cetyltrimethylammonium chloride as a template were prepared by solvent evaporation method. The effects of H2O/TEOS molar ratio and drying temperatures on the macroscopic morphology and mesostructure were investigated. Higher H2O/TEOS ratio and higher drying temperature gave a more transparent and smooth-surfaced product. With increasing H2O/TEOS ratio, the order of the mesostructure in the product film was reduced, resulting from the slow formation of surfactant mesostructure and fast silicate gelation. The pore size showed an increase with increasing H2O/TEOS ratio, suggesting mediation by the water layer between the micellar surface and the silicate. The drying temperature affected the rate of silicate condensation and the solvent evaporation, both factors that influenced the mesostructuralization of surfactant molecules. A high drying temperature facilitated the gelation of silicate rather than the evaporation of solvent, resulting in a less ordered mesostructure.

Effects of catalytic acid and templating surfactant concentrations on mesostructure of submillimeter-thick mesoporous silica by solvent evaporation synthesis

Abstract Submillimeter-thick films of mesoporous silica were synthesized by the solvent evaporation method using tetraethoxysilane (TEOS) and cetyltrimethylammonium chloride (CTAC) as the silica source and the templating agent, respectively. The effects of HCl/TEOS and CTAC/TEOS molar ratios were investigated. It was revealed that a high CTAC concentration and a low gelation rate at a low HCl concentration were favorable for the formation of highly ordered mesostructures, since the mesostructure is governed by the concentration of CTAC at gelation of the solution. The pore diameter increased as the CTAC/TEOS ratio decreased, suggesting the intermediation between a silica wall and a CTAC micelle by a water layer whose thickness increases with the increase in the H 2 O/CTAC ratio.

Structure and formation process of silica microparticles and monolithic gels prepared by the sol-gel method

Abstract Silica microparticies and monolithic gels were prepared via the hydrolysis and polymerization of tetraethylortho silicate (TEOS) with NH3 as the catalyst. The scanning electron microscope (SEM) observations revealed that the microparticles were formed through the aggregation of smaller particles. In the small angle X-ray scattering (SAXS) measurements, an abrupt change in the power dependence of the scattered intensity on the wave number was observed, which suggests that both the microparticles and monolithic gels were formed via multi-staged aggregation. Elementary silica particles first assemble into a fractal precursory aggregate, and a further aggregation of the precursory aggregates leads to the resultant structure. The fractal dimensionality of those precursory aggregate was estimated as approximately 1.5, in common both for the formation of the silica dispersed microparticies and monolithic gels.

Modified polysulphone membranes: 1. Pervaporation of water/alcohol mixtures through modified polysulphone membranes having methyl ester moiety

Abstract Membranes were prepared from modified Udel P-3500 polysulphone having methyl carboxylate groups, of which the degree of substitution ranged from 0.05 to 1.90 ester groups per repeat unit. The membranes showed permselectivity towards water in the pervaporation of aqueous alcohol solutions.

Effect of addition of polymeric species with ether moieties on porous structure of silica prepared by sol-gel method

The authors have investigated the effect of the addition of polymeric species (polyethyleneglycol, polypropyleneglycol and polytetramethyleneoxide) containing ether moieties in their main chain on the silica porous structure yielded via the sol-gel method. The obtained silica porous structures were characterized by nitrogen adsorption/desorption and SEM. Introducing those polymeric species apparently enhanced the pore formation. The enhancement is more noticeable for higher concentrations of the polymeric species, distributed from the microporous to mesoporous regions. The pore diameter at which the pore enhancement is induced by adding the polymeric species reduces with the fraction of ether moiety. Adding the polymeric species prior to the onset of the hydrolysis of tetraethylorthosilicate (TEOS) was necessary for the enhancement in the mesoporous region to takes place. The pore enhancement was more outstanding when HCL was used as the catalyst for the hydrolysis of the alkoxide than NH3. The mutual affinity between the added polymeric and silica species is considered as an important factor of the pore generation in the micro- and meso-porous regions.

Preparation of nanoporous ZnO using copolymer gel template

Mesoporous ZnO were prepared using copolymer gel template of hydroxyl ethyl methacrylate (HEMA) and ethylene glycol dimethacrylate (EGDMA) where the latter worked as the cross-linker. The effects of molar ratio [HEMA]/[EGDMA] in copolymer on the porous structure of ZnO formed in the template gel were investigated. The results indicated that the pore size and its distribution of the mesoporous ZnO could be drastically varied by [HEMA]/[EGDMA] molar ratio which directly affects the templating gel structure. Smaller pores and narrow pore size distribution were obtained with the molar ratio increased. The formation mechanism of mesoporous structure was discussed based on these experimental results.