• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.621-623
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• 2015

This article describes a purification method yielding high purity of MFB produced from DMT production process. Aldehyde functional group of MFB included in side-products were converted to acetal compound via reacting with methanol and further separated. Hydrolysis process of the acetal product was continued under acidic condition and highly pure MFB were obtained with 90% yield. The structure of MFB was analyzed by $^1H$ NMR and $^{13}C$ NMR spectroscopy. Also, the purity of MFB was estimated to be over 99% by GC analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1914-1922
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• 2002

Operating test of power-transmission plastic spur gears were performed inspecting both characteristics of friction-wear and endurance, and suggesting endurance improvement method that either drills internal holes of tooth or inserts metallic pin in the internal hole of tooth and verifying this newly-provided method. In case of acetal gears, amount of friction-wear is observed to increase by development of plastic deformation and increase of tooth stiffness due to brittle material property of acetal. To the contrary, in case of nylon gears, suggested method is shown to drop down the tooth temperature for about 3∼10$^{\circ}C$ than original gear, thus amount of wear is reduced by over 30% and operating lift prolonged by more than 200%. Hence, suggested method is proved to be practically applicable to the plastic gears made by soft polymers such as Nylon.

• Bulletin of the Korean Chemical Society
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• v.25 no.7
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• pp.1075-1077
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• 2004

• Journal of the Korean Society of Industry Convergence
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• v.6 no.1
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• pp.17-21
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• 2003

5원환 고리아세탈 화합물인 4-methylenes(4,5)을 합성하고 저온조건 하에서 중합반응을 조사한 결과, 선택적인 개환중합이 일어났다. 보통의 양이온 개시제를 사용한 결과 $-78^{\circ}C$에서 가교체가 얻어졌으며, $CH_3SO_3H$를 개시제로 사용하면 같은 조건에서도 주사슬과 곁사슬에 이중결합을 가지는 개환중합체가 얻어진다. 이 중합체는 반응성을 가지는 불포화기를 포함하고 있으므로 prepolymer로써 널리 사용될 수 있다.

• Bulletin of the Korean Chemical Society
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• v.20 no.7
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• pp.801-804
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• 1999

Thermal and photoinduced silylallylation reactions of organic halides with 3-stannyl-2-(silylmethyl)propene are explored. Silylallylations occur in moderate to high yields, producing various functionalized allylsilane products in which halide carbon is bonded to the terminal alkenic carbon of allylsilane with the removal of tributyltin group. The reactions, which tolerate functional groups such as carbonyl, ester, nitrile, acetal, and ketal, hold synthetic potential for the construction of functionalized allylsilanes.

• Proceedings of the PSK Conference
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• 2003.10a
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• pp.50-53
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• 2003

Aceclofenac (AFC) as a model has poor solubility in water, resulting in lower dissolution rate and bioavailability. A solid dispersion (SD) is one of effective methods to enhance the solubility or dissolution rate of various poorly water-soluble drugs. Polyvinylpyrrolidone (PVP) that is a nontoxic, water-soluble and generally applicable pharmaceutical excipient has been widely used as a carrier in the preparation of solid dispersions. (omitted)

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1218-1242
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• 2002

Photochemical reactions of aromatic carbonyl compounds with silyl ketene acetals have been explored. Irradiation of acetonitrile or benzene solutions containing aryl aldehydes or ketones in the presence of silyl ketene acetals is observed to promo te formation of ${\beta}-hydroxyester$, 2,2-dioxyoxetane and 3,3-dioxyoxetane products. The ratios of these photoproducts, which arise by competitive single electron transfer (SET) and classical Paterno-Buchi mechanistic pathways, is found to be dependent on the degree of methyl-substitution on the vinyl moieties of the ketene acetals in a manner which reflects expected alkyl substituent effects on the oxidation potentials of these electron rich donors. An analysis of the product distribution arising by irradiation of a solution containing butyrophenone (6) and the silyl ketene acetal 9, derived from methyl isobutyrate, provides an estimate of the rate constants for the competitive Norrish type Ⅱ, SET and Paterno-Buchi processes occuring. Finally, sequences involving silyl ketene acetal-aryl aldehyde or ketone photoaddition followed by 2,2-dioxyoxetane hydrolysis represent useful procedures for Claisen-condensation type, ${\beta}-hydroxyester$ synthesis.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.1
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• pp.42-52
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• 2002

The purpose of this study was to evaluate the bond strength of reline resin to pressure injection type thermoplastic denture base resin. The denture base resins used in this study were $Hi-polycarbonate^{(R)}$(High Dental Co., Japan), Acetal $dental^{(R)}$(Pressingdental s.r.1., Repubblica di San Marine) of thermoplastic resin and Acron $MC^{(R)}$(GC Dental Industrial Co., Japan) of heat cured resin. The reline resins used were Lucitone $199^{(R)}$(Dentsply international Inc., USA), Tokuso $rebase^{(R)}$(Tokuyama Corp., Japan), and $Lightdon-U^{(R)}$(Dreve-Dentamid-Gmbh, Germany). The reline resins are representative of heat-cured, self-cured, and light-cured resin respectively Bond strength was examined by use of a three-point transverse flexural strength test. The results were as follows 1. The bond strength of Lucitone 199 to Acron MC was the highest. 2. The bond strengths of Lucitone 199 and Tokuso rebase to Hi-polycarbonate resulted in a value of approximately one half that of Lucitone 199 to Acron MC and there were no significant differences between these and the bond strength of Tokuso rebase to Acron MC(p<0.05) 3. The bond strengths of reline resins to Acetal dental were lower than those of reline resins to Hi-polycarbonate. 4. For all base resins Lightdon-U showed lower bond strength than the other reline resins.

• Journal of the Korean Chemical Society
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• v.7 no.2
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• pp.96-105
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• 1963

The weight decrease curves of 18 kinds of polymers have been measured by thermobalance at the same condition where temperature is increased $1^{\circ}C$ per minutes under nitrogen or air atmosphere. The curves are further differentiated to obtain rate curve of weight decrease. Those curve offer a method to compare relative thermal stability, effects of oxygen or modes of thermal degradation of polymers qualitatively. The curves could be classified into following four types: Polystyrene, polymethylmethacrylate and acetal polymer belong to the first type. Those polymers depolymerize mainly into corresponding monomers, weight decrease curves are steepy up to perfect vaporization of polymers and rate curves show a relatively sharp peak. (Type I) Polyvinyl chloride represents the second type. This polymer decomposes with splitting off of hydrogen chloride. The thermogravimetric curve rises rapidly at first, then level off at the moderate weight decrease and gradually rises. Polyvinyl acetate also belongs to this class. (Type II) The modification of the second type is represented by polyester. The curve at the early stage is less steep, the leveling off at the next stage is less clear and the final rising of the curve is steeper than the normal second type. Polyamide, polyurethane, and polycarbonate belong to this type. (Type II') The thermal decomposition of the third type polymers is more complex than that of others. Various irregular chain scissions including side chain splitting and depolymerization to monomers occur simultaneously. The weight of the polymer decreases gradually and the rate curve does not show sharp peaks. Polyvinyl alcohol and diene polymers belong to this type. (Type III) Generally, polycondensation polymers are more stable toward heat than addition polymers and polymers having aromatic nucleus show good thermal stability. Polymers having tertiary carbon atoms such as polystyrene or polypropylene and acetal resin start decomposition under airatmosphere at the temprature below $50^{\circ}C$ or more of the temperature where the polymers start decomposition under nitrogen atmosphere.

• Korean Journal of Pharmacognosy
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• v.40 no.4
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• pp.334-338
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• 2009

Six iridoids were isolated from the 70% ethanol extract of Lonicera Caulis (Caprifoliaceae) and their structures were identified as epialyxialactone (1), secologanin dimethyl acetal (2), sweroside (3), loganin (4), loganic acid (5) and demethylsecologanol (6). The chemical structures of these compounds were identified on the basis of spectroscopic methods and comparison with literature values. This is the first report of the iridolactone, epialyxialactone (1), from the Caprifoliaceae plants and loganic acid (5) and demethylsecologanol (6) from Lonicera Caulis.