Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Patent
1993-04-02
1995-03-07
Kuhns, Allan R.
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
264126, B29C 6704
Patent
active
053955625
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of producing high-strength sintered products from mesocarbon (mesophase carbon) microbeads (hereinafter referred to briefly as MCMB).
The invention also relates to a method for controlling the quality of sintered MCMB bodies.
BACKGROUND ART
A well-known method of evaluating the quality of MCMB is an analysis using solvents. This method evaluates the quality of MCMB using, as indices, the percentages (by weight) of toluene-insoluble fraction (TI), quinoline-insoluble fraction (QI) and .beta.-resin [TI-QI].
However, for the quality evaluation of MCMB, this method is not wholly satisfactory. While what matters in the application of MCMB is the flexural strength of sintered bodies obtainable by sintering the MCMB at a temperature not below 1,000.degree. C., there actually exist MCMB species showing substantially the same TI, QI and .beta.-resin percentages and yet giving widely different flexural strength values after sintering at 1,000.degree. C. or above. The reason for this variation is presumably as follows. The binding component of MCMB is so reactive and susceptible to oxidation that the MCMB is ready to undergo oxidative degradation. Compared with unoxidized MCMB, MCMB that has undergone low-temperature oxidation yields a considerably lower flexural strength value after firing at 1,000.degree. C. or above, even though its TI, QI and .beta.-resin contents remain almost unchanged from the unoxidized MCMB.
The only reliable method available today for the quality evaluation of MCMB comprises taking a sample of MCMB from a lot in question, subjecting it to pressure-molding under a given pressure load, sintering the molding at 1,000.degree. C. and measuring the flexural strength of the sintered body. No method is available for predicting the characteristics of a 1000.degree. C.-sintered body from the characteristics of raw MCMB.
Furthermore, in some instances, the pressure-molded MCMB swells in the course of firing up to 1,000.degree. C., thus failing to give satisfactory sintered products of practical value. There is no method, either, for prognosticating, based on the characteristics of unprocessed MCMB, whether such swelling would occur or not.
DISCLOSURE OF THE INVENTION
The present invention provides a method of producing sintered products from MCMB, viz.:
A method of producing shaped and sintered high-strength products from MCMB which comprises subjecting MCMB with an MSP (maximum solubility percent) of 30 to 38% by volume to pressure molding and, then, to sintering, where "MSP" represents the percentage reduction in volume (% by volume) upon heating a given amount of MCMB to 350.degree. C. at a pressure of 10 kgf/cm.sup.2.
More particularly, the index MSP employed herein to express an important characteristic of MCMB is defined as follows: MCMB is placed in a vessel and subjected to a pressure of 10 kgf/cm.sup.2 at atmospheric temperature and V.sub.2 is the volume of the MCMB when the same is heated to 350.degree. C. at a constant pressure of 10 kgf/cm.sup.2.
The present invention further provides a method for controlling the quality of shaped and sintered products of MCMB, viz.:
A method of controlling the quality of a pressure-molded, sintered MCMB body which comprises heating MCMB in a given space under a given pressure load and determining its percent reduction in volume (MSP).
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagrammatic representation of the relationship between the amount (% by weight) of QS (quinoline-soluble fraction) in unoxidized MCMB immediately after production thereof in an N.sub.2 or inert gas atmosphere and the flexural strength (kgf/cm.sup.2) of the corresponding molded body sintered at 1,000.degree. C.
FIG. 2 is a diagrammatic representation of the relationship between the amount of QS (% by weight) in MCMB allowed to stand in the air and the flexural strength (kgf/cm.sup.2) of an MCMB sintered body obtained by firing at 1,000.degree. C.
FIG. 3 is a diagrammatic representation of the relationship between
REFERENCES:
patent: 4950443 (1990-08-01), Kawakubo et al.
patent: 4985184 (1991-01-01), Takahashi et al.
patent: 5046703 (1991-09-01), Kamiyama et al.
patent: 5169718 (1992-12-01), Miura et al.
patent: 5202293 (1993-04-01), Okamoto et al.
Azuma Takayuki
Mimura Noboru
Minamitani Yasuo
Murakami Norio
Murakami Tadashi
Kuhns Allan R.
Osaka Gas Company Ltd.
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