Masaaki Yoshikawa

Physical and chemical properties of pitch fluoride prepared by direct fluorination

Abstract Various physical and chemical properties of pitch fluoride such as chemical composition, molecular weight, specific gravity, dielectric constant, and water- and oil-repellency have been investigated as functions of the fluorination temperature between 30 °C and 130 °C. Bulk properties such as chemical composition, molecular weight, specific gravity and interlayer spacing vary according to the reaction temperature, while the surface properties are independent from it. Each property may be summarized as follows: chemical compositions were between CF1.00 and CF1.59; molecular weights were in the range 2070–4300; specific gravity was c. 2.00; refractive index was in the range 1.36–1.39; dielectric constant was c. 2.0. The contact angle of water was almost constant at c. 143°, demonstrating the excellent water-repellency.

Transparent carbon-fluorine compounds prepared by the heat treatment of pitch fluoride under a fluorine atmosphere

Abstract Pitch fluoride prepared from mesophase pitch at 70 °C was heat treated in a fluorine atmosphere over the temperature range from 200 to 400 °C. The compounds obtained were a colorless transparent solid with a composition between CF 1.38 and CF 1.50 , and a liquid fluorocarbon which was colorless and transparent. The yields of both compounds depended on the heat-treatment temperature. From 200 to 280 °C, the solid compound was obtained as the main product, together with the liquid fluorocarbon as a by-product. Above 280 °C, the liquid compound was the main product and the solid the by-product. The liquid compound was selectively obtained at 400 °C. These compounds are composed of chair-type condensed cyclohexane rings with CF 2 , CF 3 CF 2 - and CF 3 CF- groups in the periphery of the rings. The difference between these compounds is mainly in their molecular weights.

New fluorocarbon materials by direct fluorination of pitch

Abstract Graphite fluorides, (CF)n and (C2F)n are well known as the products by direct fluorination of graphite, and have already been commercialized as the cathode mass of lithium batteries, etc. These compounds are generally prepared from rather well ordered carbon at temperatures higher than 350°C. In the present study, pitches which are precursor materials of graphite were reacted with fluorine by a substitution and an addition reaction in fluorine gas(F2) at lower temparature than 100°C. Pitch fluoride is a novel fluorocarbon having excellent properties comparable or superior to those of graphite fluorides, (CF)n, (C2F)n and PTFE. Pitch + F2 → Pitch fluoride (H/C=0.5) (F/C=0.8 − 1.6) - Powdery form - Glass form - Mean molecular weight 1,000 – 3,000 Features 1. Outstanding properties similar to those of graphite fluoride. 2. Producted by a economical manufacturing process. (Low reaction temperature, short reaction time) 3. Possesses excellent water repellant properties. Contact angle of water for pitch fluoride is 145°. 4. Thin films can be formed with vacuum deposition processes. 5. Pitch fluoride is soluble in some solvents and has a wider range of applications.

A new type of liquid fluorocarbon prepared by direct fluorination of coal tar pitches

Abstract We have reported that new fluorocarbon materials were synthesized by direct fluorination of various coal tar pitches. This method has the advantage of low initial cost and simple processing. Recently, we found a liquid fluorocarbon is also prepared by a two-step direct fluorination of pitch. In the first step, raw coal tar pitch is fluorinated by elemental fluorine below 100 °C. In this step, fluorine atoms substitute for hydrogens and add to Cue5fbC double bonds to yield a solid type fluorocarbon, as nearly perfluorinated pitch. This compound shows high inertness to very strong Lewis acids, such as fluorine at room temperature. In a second step, the compound obtained is placed under a fluorine atmosphere again, but at temperature higher than 150 °C. In this step, further fluorination proceeds rapidly at new active sites as well as the residual Cue5fbC double bonds which remain in the solid compound. The cracking caused by ring-opening reactions and the cleavage of Cue5f8C bonds occur at the same time. As the result, the liquid fluorocarbon is formed, which has a lower average molecular weight and higher fluorine content than the solid compound. The average structure of the liquid is shown as follows. The fluorine atoms are bonded to the carbon atoms which form the 2 or 3 chair-type condensed cyclohexane rings.

Chemical properties of new fluorinated carbon materials from pitch

Abstract In previous work, new fluorinated carbon materials were synthesized by direct fluorination of various coal tar pitches. But there were always problems in that process because of large generation of heat. Then we try to control the reaction temperature by flow rate of F 2 and cooler set in the reactor. As a result, two types of fluorinated pitches were synthesized at different reaction temperatures, a low-temperature type (L) and a high temperature type (H). The result of elemental analysis showed that F/C ratio of the type (H) is larger than that of the type (L). The type (H) shows whiter color than the type (L). This result seems to be concerned with the amount of the residual double-bonds in the fluorinated pitch. 19 Fue5f8NMR spectra showed that the type (H) has more amount of −CF2 CF3 chemical shift. It is considered by the ring-opening reaction because starting pitch has few ethyl-chain. Therefore the high temperature condition seems to produce the more ring-opening reaction. Mean molecular weights by VPO measurement showed that Mw. of the type (H) is about 3,000. That value is in accordance with the estimated value by Mw. of starting pitch and F/C. On the other hand, that of the type(L) reaches about 5,000, which indicates a form of recombinations of cleaved bonds through low temperature condition and stable fluoination.