Catalyst – solid sorbent – or support therefor: product or process – Solid sorbent – Organic
Reexamination Certificate
2001-11-21
2003-06-03
Foelak, Morton (Department: 1711)
Catalyst, solid sorbent, or support therefor: product or process
Solid sorbent
Organic
C264S029100, C264S029400, C264S029500, C264S029700, C423S447400, C423S447900, C522S038000, C521S084100
Reexamination Certificate
active
06573215
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to porous material suitable for use in bearing rolling elements, and more particularly, to a porous material suitable for use in a bearing rolling element, obtained by a process comprising the steps of mixing degreased bran derived from rice bran with a thermosetting resin before kneading, subjecting a kneaded mixture to a primary firing in an inert gas at a temperature in a range of 700 to 1000° C., pulverizing the kneaded mixture obtained after the primary firing into carbonized powders sieved through a screen of 100-mesh, mixing the carbonized powders or the carbonized powders and ceramic powders with a thermosetting resin before kneading, pressure-forming a kneaded mixture thus obtained at a pressure in a range of 20 to 30 MPa, and applying a heat treatment again to a formed kneaded mixture in the inert gas at a temperature in a range of 100 to 1100° C.
2. Description of the Related Art
Alloy, and ceramics such as silicon nitride, and so forth have been in widespread use up to now as a material for a rolling element of bearings such as ball bearings, roller bearings, and so forth. The material for the rolling element of such bearings is required to have surface hardness, a small thermal-dimensional-change characteristic, and so forth besides mechanical strength. An alloy-based material naturally comes to have a higher density, causing degradation in bearing characteristics at the time of acceleration due to weight thereof while ceramics are not only susceptible to impact and expensive although low in density but also electrical insulators, thereby requiring means for prevention of electrostatic buildup.
Meanwhile, an attempt to obtain a porous carbonaceous material by utilizing rice bran discharged in quantity of 900, 000 tons a year in Japan and 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 and kneading degreased bran derived from rice bran with a thermosetting resin, drying a formed kneaded mixture prepared by pressure-forming, and firing the formed kneaded mixture as dried in an minert gas, and a method of producing the same.
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 pressure-forming to those of a finished formed product obtained after the firing in the inert gas.
SUMMARY OF THE INVENTION
The invention has been developed to solve the problem described above, and it is therefore an object of the invention to provide a porous material suitable for use in a bearing rolling element, having such properties as a small contraction ratio of the dimensions of a formed workpiece formed thereof to those of a finished product, excellent electric conductivity, small thermal strain, insusceptibility to damage, light weight, a long service life, and still ability to retain oil and grease for a long period of time, thereby providing a high-tech eco-material (state-of-the-art material excellent in ecological adaptability) utilizing biomass resources, different from conventional industrial material.
The inventors have been successful in development of a porous material suitable for use in fabricating a high-precision bearing rolling element having excellent properties as material for use in fabricating the bearing rolling element, and a small contraction ratio of the dimensions of a formed workpiece formed thereof to those of a finished product.
The inventors have found out that it is possible to obtain a porous material suitable for use in a bearing rolling element, having such properties as a small contraction ratio of the dimensions of a formed workpiece formed thereof to those of a finished product, excellent hot oil resistance, small thermal-dimensional-change, insusceptibility to damage, light weight, a long service life, and ability to retain oil and grease for a long period of time by making effective use of the degreased bran derived from the rice bran discharged in quantity of 900, 000 tons a year in Japan and as much as 33 million tons a year throughout the world, and has thereby completed the invention.
The inventor of the present invention has conducted intense studies, and found out that a porous material is obtained by a process comprising the steps of mixing the degreased bran derived from the rice bran with a thermosetting resin before kneading, subjecting a kneaded mixture to a primary firing in an inert gas at a temperature in a range of 700 to 1000° C., pulverizing the kneaded mixture obtained after the primary firing into carbonized powders sieved through a screen of 100-mesh, mixing the carbonized powders with a thermosetting resin before kneading, pressure-forming a kneaded mixture thus obtained at a pressure in a range of 20 to 30 MPa, and applying a heat treatment again to a formed kneaded mixture in the inert gas at a temperature in a range of 100 to 1100° C., and the porous material thus obtained has ideal characteristics as material suitable for use in bearing rolling elements.
More specifically, the porous material described above has the small contraction ratio of the dimensions of a formed workpiece formed thereof to those of a finished product as low as 3% or less, 13 wt % of oil retention characteristic, 4.85×10
−3
&OHgr;cm of volume resistivity, and density in a range of 1.1 to 1.3 g /cm
3
, and further, it has been possible to obtain the porous material having Vickers hardness not less than 300~600, and still friction coefficient in the order of about 0.15 after fired at a high temperature.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Degreased bran derived from rice bran, used in carrying out the present invention, may be either of domestic origin or of foreign origin regardless of the kind of rice.
Further, any thermosetting resin may be used as long as it has thermosetting property, and typically cited as a thermosetting resin are a phenol resin, diaryl phthalate resin, unsaturated polyester resin, epoxy resin, polyimide resin, and triazine resin. In particular, the phenol resin is preferably used.
Furthermore, a thermoplastic resin such as polyamide, and so forth can be used in combination with a thermosetting resin provided that it is done without departing from the spirit and scope of the invention.
As ceramics that can be substituted for a portion of carbonized powders, there are cited Si
3
N
4
, ZrO
2
, Al
2
O
3
, SiC, BN, WC, TiC, sialon (solid solution of a Si—Al—O—N type compound), and so forth.
According to the invention, use can be made of one kind or not less than two kinds of ceramics selected from the group consisting of the ceramics described above. Ceramics not greater than 50 &mgr;m in particle size are desirable, ones not greater than 20 &mgr;m in particle size is preferable, and further, ones of particle size in a range of 0.3 to 3 &mgr;m is more preferably used.
An effect of stabilizing surface hardness is obtained by substituting ceramics not greater than 50 &mgr;m in particle size for a portion of the carbonized powders. The carbonized powders can be well mixed with ceramic powders, and a mixing ratio of the former to the latter can be 5~95:95~5 by weight.
A mixing ratio of the degreased bran to a thermosetting resin is 50~90:50~10 by weight, however, a mixing ratio of 75:25 is preferably used.
For the thermosetting resin used in this case, one in a liquid state, having a relatively small molecular weight, is desirable.
A primary firing is applied at a temperature in a range of 700 to 100° C. using normally a rotary kiln for firing time in a range of about 40 to 120 minutes.
A mixing ratio of the carbonized powders after the prim
Akiyama Motoharu
Hokkirigawa Kazuo
Obara Rikuro
Flynn ,Thiel, Boutell & Tanis, P.C.
Foelak Morton
Minebea Co. Ltd.
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