Compositions: ceramic – Ceramic compositions – Carbide or oxycarbide containing
Reexamination Certificate
2002-02-11
2004-08-17
Marcantoni, Paul (Department: 1755)
Compositions: ceramic
Ceramic compositions
Carbide or oxycarbide containing
C501S088000, C501S096400, C501S097100, C501S098100, C501S103000, C501S127000, C501S133000, C501S141000, C501S155000, C264S029100, C264S029500, C264S029600, C264S653000, C264S657000, C264S663000, C264S665000, C264S666000, C264S676000, C264S681000, C264S682000, C264S683000
Reexamination Certificate
active
06777360
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to ceramic material suitable for use in production of paving tiles, construction tiles, flooring in offices, flooring in machinery plants and so forth, and more particularly, to a ceramic material obtained by a method comprising steps of mixing defatted bran derived from rice bran with a thermosetting resin before kneading, subjecting a kneaded mixture thus obtained to a primary firing in an inert gas at a temperature in a range of 700 to 1000° C., pulverizing the kneaded mixture after the primary firing into carbonized powders, kneading the carbonized powders with which ceramic powders, a solvent, and a binder as desired are mixed into a plastic workpiece (kneaded mass), pressure-forming the plastic workpiece at pressure in a range of 10 to 100 MPa, and subjecting a formed plastic workpiece thus obtained again to firing in an inert gas atmosphere at a temperature in a range of 100 to 1400° C.
2. Description of the Related Art
In the past, porcelain clay, feldspathic clay, and silica-alumina based ceramic powders have been in widespread use for production of paving tiles, and construction tiles. Synthetic resin as represented by vinyl chloride has been in use for flooring in offices and machinery plants. However, conventional tiles have been slippery because of the hard surface thereof while flooring in offices, made of synthetic resin, have had insulating property, and been prone to generation of static electricity, so that there have been involved risks of the flooring not only giving discomfort but also causing the erroneous operation of a computer and the like. In addition, there has been a possibility of oil dropping on the floor in plants such as a machinery plant, causing workers to slip and fall on the floor. This has posed operational problems.
Meanwhile, an attempt to obtain a porous carbonaceous material by utilizing rice bran, produced in quantity of 900,000 tons a year in Japan and in as much as 33 million tons a year throughout the world, has been well known by researches carried out by Mr. Kazuo Hokkirigawa, the first inventor of the present invention (refer to “Functional Material”, May issue, 1997, Vol. 17, No. 5, pp. 24~28).
Herein are disclosed a carbonaceous material obtained by mixing defatted bran derived from rice bran with a thermosetting resin before kneading, drying a formed kneaded mixture obtained by pressure-forming a kneaded mixture, and subsequently, firing the formed kneaded mixture as dried in an inert gas, and a method of producing the carbonaceous material.
With such a method as described above, however, it has been practically difficult to form the formed kneaded mixture with precision because there occurs discrepancy in dimensions by as much as 25% in terms of a contraction ratio of the dimensions of the formed kneaded mixture prepared by the step of pressure-forming to those of a finished formed product obtained after the step of firing in the inert gas.
It is therefore an object of the invention to provide a ceramic material having such properties as a small contraction ratio of the dimensions of a formed ceramic workpiece to those of a finished product, excellent electric conductivity, small thermal strain, insusceptibility to damage, tendency of an increase in friction resistance when wet, light weight, a long service life, and ability to absorb oil and grease with ease, providing at the same time a high-tech eco-material (state-of-the-art material excellent in ecological adaptability) capable of utilizing biomass resources, which is different from the conventional industrial material.
The inventor of the present invention has found out that the ceramic material having the properties as described above can be obtained, and succeeded in development of the invention. That is, there has been developed a ceramic material having excellent properties required of ceramic material, including a small contraction ratio in the dimensions of a formed ceramic workpiece to those of a finished product, suitable for use in production of paving tiles, construction tiles, flooring in offices, flooring in machinery plants and so forth.
SUMMARY OF THE INVENTION
The inventor of the present invention has conducted intense studies, and found out that a ceramic material is obtained by a method comprising steps of mixing defatted bran derived from rice bran with a thermosetting resin before kneading, subjecting a kneaded mixture thus obtained to a primary firing in an inert gas at a temperature in a range of 700 to 1000° C., pulverizing the kneaded mixture after the primary firing into carbonized powders, kneading the carbonized powders with which ceramic powders, a solvent, and a binder as desired are mixed into a plastic workpiece (kneaded mass), pressure-forming the plastic workpiece at pressure in a range of 10 to 100 NPa, and subjecting a formed plastic workpiece thus obtained again to firing in an inert gas atmosphere at a temperature in a range of 100 to 1400° C.
More specifically, it has been possible to obtain the ceramic material described above having high compressive strength, a small contraction ratio of the dimensions of a formed ceramic workpiece to those of a finished product, which is 3% or less, 13 wt % of oil absorption ratio, low volume resistivity, and low density with Vickers hardness not less than 300 to 600.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Defatted bran derived from rice bran, used in carrying out the present invention, may be of either local origin or foreign origin regardless of the kind of rice.
Further, any thermosetting resin may be used as long as it has thermosetting property, and typical examples thereof include phenol resin, diaryl phthalate resin, unsaturated polyester resin, epoxy resin, polyimide resin, and triazine resin. In particular, phenol resin is preferably used.
Furthermore, a thermoplastic resin such as a polyamide, and so forth can be used in combination with a thermosetting resin provided that it is used without departing from the spirit and scope of the invention.
Ceramic powders to be mixed with carbonized powders in carrying out the invention are composed of any selected from the group consisting of SiO
2
, Si
3
N
4
, ZrO
2
, Al
2
O
3
, SiC, BN, WC, TiC, Sialon (Si—Al—O—N based compound solid solution), porcelain clay, feldspathic clay, kaolinite, and so forth.
In the present invention, one kind or not less than two kinds of such ceramic powders as described above may be used.
Ceramic powders not more than 50 &mgr;m in grain size are desirable, and those not more than 20 &mgr;m in grain size are preferable, those in a range of 0.3 to 3 &mgr;m in grain size being more preferably used.
Ceramic powder material as desired can be obtained by mixing the carbonized powders with the ceramic powders not more than 50 &mgr;m in grain size.
The carbonized powders can be well mixed with the ceramic powders at a ratio of 5 to 95:95 to 5 by weight.
A mixing ratio of the defatted bran to a thermosetting resin is 50 to 90:50 to 10 by weight, however, the mixing ratio of 75:25 is preferably adopted.
A thermosetting resin in a liquid state, having a relatively small molecular weight, is desirable for use in this case.
A primary firing is performed at a temperature in a range of 700 to 1000° C., using normally a rotary kiln, and a firing time is for a duration in a range of 40 to 120 min.
The carbonized powders after the primary firing can be mixed with the ceramic powders at a mixing ratio of the former to the latter of 5 to 95:95 to 5 by weight, however, if a ratio of the carbonized powders exceeds 95% by weight, the stability of the surface hardness of a formed ceramic product as obtained deteriorates while if the ratio thereof is not more than 5% by weight, electric conductivity of the formed ceramic product deteriorates.
A binder used in carrying out the present invention is broadly classified into an organic one and an inorganic one.
Examples of the organic binder are paraffin binders such as polyvinyl alcohol, polyvinyl butyral, polyethylen
Akiyama Motoharu
Hokkirigawa Kazuo
Obara Rikuro
Flynn ,Thiel, Boutell & Tanis, P.C.
Marcantoni Paul
Minebea Co. Ltd.
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