Coating processes – Coating by vapor – gas – or smoke – Carbon or carbide coating
Reexamination Certificate
1999-11-09
2001-06-12
Beck, Shrive (Department: 1762)
Coating processes
Coating by vapor, gas, or smoke
Carbon or carbide coating
C264S029200, C264S029400, C428S367000, C156S089210
Reexamination Certificate
active
06245385
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for making shaped or figured carbides which are consisted of a self-figurable flock, mass, or bulk of single fibers. More specifically, it relates to a method for making shaped or bulked carbides, in which a flock of cellulosic single fibers which has been prepared by binding the fibers by means of their intertwining properties, is heated for carbonization, whereby it can have a strong tissue afforded with high carbonic characteristics and can present porously shaped fibrous structures.
Heretofore, carbonaceous or carbon substances which are prepared from organic matters (hereinafter called generally as carbides) are employed in various industrial applications in accordance with characteristics they have, viz., adsorption, electrical, adiabatic, thermal resistant, corrosion resistant, mechanical, and other characteristics. In either of such applications, carbides have to be shaped to a form appropriate to a purpose of applications. There are known, for example, powdery, granular, and crashed carbides. And, fibrous carbides which are popularly called as carbon fibers, are available in long or lint fibrous, short or fuzz fibrous, woven, sheet or mat-like, and braided forms. In order to improve their mechanical characteristics, they are often prepared to composite materials by mixing and treating them with other materials such as resins and pitches.
In any case, in order to shape them to a form appropriate to a purpose of applications, they must be subjected to a secondary treatment process in addition to preceding carbonization process. More particularly, in case of obtaining powdery carbides, carbides have to be pulverized and sieved after carbonization, and in case of utilizing long fibrous carbides as flakes, they have to be subjected to a chopping process. And, in case of utilizing long fibrous carbides as woven or braided forms, they have to be subjected, after carbonization, to a weaving or braiding process. In such secondary processes, there are much difficulties to prepare them to a desired form. That is, as carbon fibers have inherently a poor elongation and lack in a bending force, they can tolerate to be woven only into comparatively flat stuff having little bending but not into thick and porous structures.
When short fibrous carbides which have been obtained by chopping as mentioned above, are shaped into sheets or mats by a paper-making process in which an adhesive binder is added as an auxiliary agent to the carbides so that they can be integrally shaped, they can produce only those which are flat and thin. There is observed another disadvantage that such auxiliary agent tends to adversely affect characteristics carbides properly have.
As described above, secondary processing to be adopted for shaping carbides into forms appropriate to their applications, are complex, and in certain cases, it adversely affects characteristics the carbides have and increases a production cost fruitlessly.
BRIEF SUMMARY OF THE INVENTION
Accordingly, this invention is to provide a method for making carbides which are self-shaped to have stable porous fibrous structures suitable for fully demonstrating the characteristics the carbides have and accordingly suitable to various applications, whereby such carbides are made by a simple method, at a low production cost, and without problems involved in the conventional production and employment of carbides.
More particularly, in the method for making shaped carbides of intertangled single fibers in accordance with this invention, it is characterized that porous structured raw materials which are made from a figurable intertangled mass of cellulosic single fibers, are heated, as they are shaped, in an non-oxidation atmosphere for carbonization so that entanglement among the single fibers are stiffened on account of shrinkages of the raw materials when they are subjected to the carbonization, exhibiting stable porously shaped fibrous structures. It is accordingly preferable that in respect of structural features, the cellulosic single fibers employed in this invention are those twisted, threaded, waved, curled, or frizzled, that in respect of functional features, they can get entangled easily, and that in respect of physical features, their outer surface areas are remarkably large. It is also preferable in this invention that fibrous raw materials which are made from a mass of entangled single fibers as mentioned above, are selected from a group consisted of those loose fibers, laps, slivers, and rovings which are light in weight and have porous structures.
DETAILED DESCRIPTION OF THE INVENTION
This invention is described below more in detail.
It is the first features of this invention that since the raw materials are consisted of cellulosic single fibers which are slender, have extremely large outer surface areas, and can easily get entangled each other, they can readily be shaped to a desired form of soft and porous mass of single fibers without employment of any binding agent. When such figurable raw materials are heated for carbonization as they are self-shaped, it is noticed that while the single fibers which constitute a mass of the raw materials, are converted to carbides with the progress of carbonizing reactions, they are shrinked as a whole at a constant decrement rate, keeping, continuously till the end of heat treatment, the form to which they have been shaped. This phenomena support working principles of this invention that single fibers can produce a carbonized light and porous mass, and its structures become stronger by carbonization.
While it is known that a mass of raw materials generally loses its tenacity and tends to get hardened when carbonized, an apparent hardness of the mass changes little in this invention, because only slender single fibers of a low denier constitute the mass in this invention. This is comparable to the fact that when a sheet of hard glass is converted to glass fibers, they exhibit softness.
For example, compared to those materials which are conventionally used for carbonization, such as coconut husks and sawdusts which are often employed for the manufacture of an activated carbon, single fibers employed as raw materials in this invention are extremely slender. More in concrete, a fiber width of those cellulosic single fibers which are employable in this invention, is as narrow as 0.01-0.08 mm, and their surface areas are several hundred times of those of the above-mentioned two kinds of raw materials.
Accordingly, it is the second features of this invention that carbides of a mass consisted of single fibers are extremely highly reactive, and consequently that certainly in the carbonization process and also in a process for reactivating the carbides which is conducted in case of need, their reaction speed is high and reaction proceeds evenly throughout the mass. This is one of the advantages attained by this invention.
The raw materials and carbonization treatment employed in this invention, and physical, electrical, and other properties of the carbides obtained by this invention are explained below further in detail.
The principal component of single fibers employed in this invention as raw materials, is cellulose, and their fiber width is preferably about 0.01-0.08 mm. They may be natural fibers as well as those synthetic fibers which are consisted of regenerated cellulose, such as fibers of cotton, flax, hemp, jute, ramie, paper mulberry, Edgeworthia chrysantha, bamboo sugarcane, rayon, and others.
In case of cotton fibers, for example, it is not necessary to improve their intertwining properties because they are well provided with natural twists which are spirally turned, while it is preferable to treat fibers preliminarily to carbonization, so that they will be given synthetically with waves or curls, if they are not provided with natural twists and so on. For example, such waves or curls may be given to fibers by passing them between a pair of mold rollers which are heated and face each other for pressing the fibers therebetween.
Th
Harada Ryoji
Takahashi Minoru
Beck Shrive
Fletcher, III W. P.
Shlesinger & Arkwright & Garvey LLP
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