Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1999-06-22
2002-03-19
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S455000
Reexamination Certificate
active
06358487
ABSTRACT:
TECHNICAL FIELD
The present invention relates to carbon black which is useful for various applications such as a filling material, a reinforcing material, an electroconductive material or a coloring pigment, and an effective method for its production to control physical properties thereof.
BACKGROUND ART
Carbon black has been widely used as a pigment, a filler, a reinforcing pigment or a weather resistance-improving agent. As a method for its production, a furnace type production method by using a cylindrical carbon black producing furnace is widely known wherein in a first reaction zone, an oxygen-containing gas and a fuel are introduced in the furnace axis direction or in the tangent direction; while a high temperature combustion gas stream obtained by burning them is moved to a second reaction zone provided downstream to the first reaction zone in the furnace axis direction, a feed stock is introduced to the gas stream to form a carbon black; and the reaction gas is quenched to terminate the reaction in a third reaction zone.
Carbon black to be used as a coloring agent for resin coloring agents, printing inks or coating materials, is desired to be excellent in blackness, dispersibility, gloss and coloring power. Further, carbon black to be used mainly as a reinforcing agent for tires for vehicles is desired to be excellent in wear resistance.
Carbon black particles usually exist in a state where particles fuse each other such as the spitted doughboys, and each spherical particle merely characterizes the hill and the dale between doughboys. However, when considering it as a single particle, the particle size has a close relation with the performances in various applications, such as reinforcing property or blackness (Carbon black manual, 3rd edition, I. Abstract, page 7).
The particle size of carbon black is represented by a value obtained by direct measurement by taking a picture with several tens thousands magnifications by an electron microscope with a resolution of at least from 1.5 to 2 nm. The particle size or the first order particle size of carbon black usually means the particle size of carbon black thus measured. The particle size is within a range of from 10 to 300 nm depending upon the grade, and belongs to a region of so-called aerosol or colloid.
It is known that when carbon black is used as a black pigment, blackness and coloring power depend largely on the first order particle size of carbon black, and the smaller the first order particle size, the higher the blackness. The relation between the blackness and the first order particle size is disclosed, for example, in JP-A-50-68992. Further, it is known that when carbon black having such a small particle size is used as a reinforcing agent for tires, it shows high wear resistance.
In the case of using carbon black as a black pigment, ultrafine carbon black having a particle size of at most 15 nm has high blackness, and it is used for high grade coating materials, high grade resin coloring agents or the like. With regard to carbon black of this class, one produced by a channel method is called as HCC (High color Channel), and one produced by a furnace method is called as HCF (High Color Furnace).
Among carbon blacks of small particle size, ultrafine carbon black having a particle size of less than 14 nm has very high blackness, and used for highest grade coating materials, highest grade resin coloring agents or the like. All the articles on the market are occupied by one produced by the channel method. This may be attributable to a fact that in the channel method, carbon black of ultrafine particles having a particle size of from 13 to 14 nm, having a sharp particle size distribution, can be produced, and it shows very high blackness. Particularly in the field of high grade coating materials and high grade resin coloring agents, there is tendency that carbon black which shows highest blackness engrosses the market.
It is said that in order to obtain carbon black having a small particle size by the furnace method, it is effective to jet a feed stock into the high speed gas stream in the choke part installed in the second reaction zone, to atomize the liquid supplied material, by the kinetic energy and heat energy of the gas.
For example, JP-B-54-10358 describes that in order to effectively atomize and disperse the liquid introduced hydrocarbon, it is advisable that combustion gas flow rate at the part of jetting the liquid introduced feed stock is at least Mach 0.35, preferably within a range of from Mach 0.4 to Mach 0.8.
It is considered that for effective atomization and dispersion of the liquid feed stock, the higher the flow rate at the part of introducing the liquid feed stock, the better. However, in the case of attempting to obtain higher flow rate at the part of introducing the feed stock, when the flow rate at the part of introducing the feed stock is increased to nearly sound speed, for example, a significant pressure drop is brought about in the entire furnace. Particularly, in the case of jetting the feed stock in a relatively long choke part, the pressure drop tends to be large, and it will be unavoidable to significantly raise the performance of the peripheral equipment such as a blower for combustion air. Further, when the combustion gas is introduced into the choke part at a high speed, the part where the combustion gas directly or indirectly strikes, such as the choke inlet, will be damaged by the kinetic energy of the gas. Accordingly, it is desired to establish a method to raise the flow rate of the combustion gas at the part of introducing the feed stock to be from Mach 0.8 to Mach 1, without significant increase in the pressure drop or significant damage of the apparatus.
Further, it has also been known that carbon black having a small particle size can be obtained when the amount of material oil injected is made to be small relative to the amount of the combustion gas. However, the proportion of the material oil injected is small, productivity of carbon black decreases. As a method not to decrease the productivity, it has also been known to be effective to raise the temperature of gas at the region of injecting the material oil for effective production of carbon black having a small particle size. In such a case, in the production of furnace black, it is common to leave a certain amount of remaining oxygen in the gas at the part of injecting the starting oil, to partially burn the starting oil itself, thereby the temperature at the region of carbon black production is raised. However, with the method, a part of the material oil injected is used in the combustion reaction and is not formed into carbon black, thereby the yield tends to be low.
Accordingly, it is difficult to constantly produce one having a particle size of about 11 to about 14 nm with the conventional techniques of the furnace method. Even if one having a particle size of smaller than that can be produced, the particle size distribution is broad, and the same level of blackness as channel black can not be obtained. Further, in order to obtain one having a small particle size, it is necessary to extremely decrease the amount of the feed stock injected in the furnace relative to the amount of the combustion gas generated in the furnace, and as a result, the yield of the product will extremely decrease.
Further, in order to obtain high blackness with the conventional techniques of the furnace method, it is necessary not only to make the particle size small, but also to decrease a DBP oil absorption as a index of development of aggregate as mentioned hereinafter. As a method to make the DBP oil absorption small, usually an alkali metal salt or its solution is added into the material oil, or it is introduced into the combustion zone or the reaction zone. However, if the DBP oil absorption decreases, particularly in the case of blending carbon black in a vehicle for coating materials or in a resin, there are defects that dispersibility or fluidity deteriorates.
Heretofore, several reports have been made with regard to trials to pr
Fukuyama Yutaka
Ishida Masanobu
Maeda Hiroshi
Mise Nobutake
Nakajima Susumu
Hendrickson Stuart L.
Mitsubishi Chemical Corporation
LandOfFree
Carbon black and process for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Carbon black and process for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbon black and process for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2857243