Carbon black

Details Carbon black Carbon black

2000-01-21

2001-09-18

Koslow, C. Melissa (Department: 1755)

Compositions: coating or plastic

Materials or ingredients

Pigment, filler, or aggregate compositions, e.g., stone,...

C106S473000, C106S474000

Reexamination Certificate

active

06290767

ABSTRACT:

INTRODUCTION AND BACKGROUND
The present invention relates to a carbon black, its preparation and its use.
Carbon blacks are used on a large scale as a black pigment and as a reinforcing agent and filler. They are produced with different properties by various processes. Most frequent is preparation by means of oxidative pyrolysis of carbon-containing carbon black raw materials. In that process, the carbon black raw materials are burnt incompletely at high temperatures in the presence of oxygen. This class of carbon black preparation processes includes, for example, the furnace black process, the gas black process and the lamp black process. The carbon-containing carbon black raw materials used are predominantly polynuclear aromatic carbon black oils. The product stream of oxidative pyrolysis consists of a waste gas containing hydrogen and carbon monoxide and, suspended therein, finely divided carbon black, which is separated from the waste gas in a filtering installation.
In the furnace black process, incomplete combustion takes place in a reactor lined with highly refractory material. A stream of hot waste gases is produced in a pre-combustion chamber by burning a fuel/air mixture, and the carbon black raw material is sprayed or injected into that stream. The carbon black that forms is quenched by the spraying of water into the reactor and is separated from the stream of gas. The furnace carbon black process permits the preparation of carbon blacks having a very wide range of carbon black properties.
The lamp black apparatus consists of a cast-iron shell, which receives the liquid or, optionally, molten raw material, and a closed hood having a refractory lining. The air gap between the shell and the closed hood, as well as the low pressure in the system, serve to regulate the supply of air and hence to influence the properties of the carbon black. As a result of the heat radiation of the closed hood, the raw material vaporizes and is partly burnt but mainly converted into carbon black. In order to separate off the carbon black, the process gases containing carbon black are passed into a filter after cooling.
In the gas black process, the carbon black raw material is first vaporized into a hydrogen-containing carrier gas stream and then burnt in a plurality of small flames beneath a cooled roller. Some of the carbon black that forms is deposited on the roller and some is discharged with the process gases and removed in a filter.
The mentioned processes for preparing carbon black are known from Ullmanns Enzyklopädie der technischen Chemie 4. edition Volume 14 page 633 ff.
All three processes may in principle be used within the context of the invention, but preference is given to the furnace process.
It is known to dope carbon black with silicon. Carbon blacks doped with silicon are known, for example, from WO 96/37547. Silicon-containing carbon blacks can be prepared, for example, by adding silicon-containing compounds to the carbon black raw material.
It is further known to dope carbon black also with other elements (U.S. Pat. No. 3,448,052; EP 278 743 A1; EP 829 511 A1). The doping processes are similar to silicon doping.
Aggregates consisting of a carbon black phase and a metal-containing phase are known from WO 98/42778.
Also known is a process for the preparation of an intimate mixture of carbon black with oxides of the elements boron, silicon, aluminum, titanium, zirconium, zinc, lead, tin, iron, cobalt, nickel, manganese, chromium, vanadium, molybdenum, niobium and tantalum (U.S. Pat. No. 3,094,428).
There is further known a process for the preparation of carbon black by introduction of a metal compound of the group gallium, indium, aluminum or mixtures thereof (U.S. Pat. No. 3,306,762). The addition of those metal compounds, like the addition of alkali metal compounds, brings about a lowering of the structure.
Also known is a process for the preparation of carbon blacks by addition of rare earths having atomic numbers from 57 to 71 (U.S. Pat. No. 3,383,175).
An object of the present invention is to make available a carbon black having special properties such as, for example, changed shade of color, changed electrical properties, changed pH value, functional groups, sites of reaction, and improved dynamic properties in rubber. A further object is to influence the structure of the carbon black.
SUMMARY OF THE INVENTION
The above and other objects of the invention can be achieved by carbon blacks doped with elements that are not carbon, wherein pairs of carbon atoms have been replaced by isoelectronic pairs of elements or combinations of elements. The isoelectronic pairs of elements or combinations of elements can include different elements.
The carbon black can contain a combination of elements consisting of a trivalent element and a pentavalent element.
According to the invention, the carbon black can contain from 0.01 to 50 wt. % of the isoelectronic pairs of elements or combinations of elements, based on the total weight. The elements can be in a molar ratio of from 0.5/1 to 1/1.5, preferably from 0.8/1 to 1/1.2.
The carbon blacks can additionally be doped with other elements, preferably silicon.
The carbon black of the invention can contain B/N, Al/P and/or Ga/As as the combination of elements.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention, the carbon black can be prepared by incorporating isoelectronic BN into the carbon of the carbon black.
According to the invention, at least two adjacent carbon atoms as a C═C unit are always replaced by an inseparable combination of elements, which are dependent on each other for the purposes of the desired doping, consisting of two isoelectronic elements, preferably of main groups III and V. They may be present in the carbon black approximately in equal proportions (with a certain tolerance). The combination is isoelectronic with C═C and forms the same structures. Thus, for example, aromatic or graphite-like structures, triple coordination and formation of double bonds may be present.
Silicon as a higher homolog of carbon is able to replace a single position of a carbon atom. Two adjacent silicon atoms therefore do not represent a combination of elements within the scope of the invention. Nor are they able to bring about an uneven charge distribution, as can be achieved by the combinations of elements of the invention.
In an embodiment of the invention of such a combination that is isoelectric with C═C, BN may be used.
Boron nitride (BN) exists in three modifications:
&agr;-BN, analogous to graphite, hexagonal
&bgr;-BN, analogous to diamond, cubic
&ggr;-BN, analogous to graphite, but metastable.
The unit BN is isoelectronic with C
2
. The properties of the boron nitrides are very similar to those of the carbon forms. Analogously to diamond, &bgr;-BN is very hard and is used as an abrasive. In the case of &agr;-BN, the regular expression is “white graphite”, since it is a soft modification having a layered construction, which can be used as a high-temperature lubricant. There also exist BN-analogous benzene, borazole and BN nano tubes.
The carbon black of the invention can contain a structural element according to formula I.
Although the totality of the two elements leaves neither a surplus nor a deficit of electrons in total, the electrons here are distributed unevenly within the unit. This can lead to the electron distribution in the carbon black being disturbed, with the result, for example, that the aromatic system of the carbon is disturbed and new properties are produced.
The combinations of elements may be evenly distributed in the carbon black or may be concentrated at the surface. They may be randomly distributed or may form clusters. They may form part of the carbon framework or be present separately next to the carbon structures.
The invention also provides a process for the preparation of carbon blacks, wherein compounds of the trivalent elements and compounds of the pentavalent elements are introduced into the carbon black preparation process simultaneously, optionally with the addit

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