US3282718A

US3282718A - Carbonaceous material

Info

Publication number: US3282718A
Application number: US261861A
Authority: US
Inventors: Mark J Smith
Original assignee: Air Reduction Co Inc
Current assignee: Airco Inc
Priority date: 1963-02-28
Filing date: 1963-02-28
Publication date: 1966-11-01
Anticipated expiration: 1983-11-01

Description

United States Patent 3,282,718 CARBONACEOUS MATERIAL Mark J. Smith, Wilson, N.Y., assignor to Air Reduction Company, Incorporated, New York, N.Y., a corporation of New York No Drawing. Filed Feb. 28, 1963, Ser. No. 261,861 9 Claims. (Cl. 106-269) This invention relates to a novel carbonaceous material from which continuous extrusions of predetermined shapes can be made, and to a novel method of preparing such material. The invention further relates to novel lubricants for making carbonaceous mixtures readily ext-laudable at favorable temperatures and pressures.

In conventional methods, carbon and graphite is made from a mixture of carbon filler and a hydrocarbonaceous binder such as coal-tar pitch. The filler may, for example, consist of petroleum coke, pitch coke, graphite [flour or carbon black. Before the mixture is extruded and subsequently baked or graphitized, a lubricant is added to effectively lower the viscosity of the mixture so that the extrusion pressure required for forcing the mixture through a die of predetermined shape is significantly reduced. Unfortunately, these methods of extruding carbonaceous mixtures have objectionable features which are well known and which are due largely to the type of lubricants used. Some prior art lubricants comprise petroleum derivatives in the form of highly viscous oils; other lubricants contaminate and reduce the adhesive property of the coal-tar pitch, and leave an undesirable residue in the finished article. In any event, these lubricants have not proved entirely satisfactory for large scale commercial production.

One object of this invention is to provide an improved method of rapidly extruding carbonaceous mixtures of predetermined shape; another object is to effect the rapid extrusion of carbonaceous mixtures at favorable pressures and temperatures by incorporating selective lubricants therein; a further object is to provide selective lubricants to decrease the effective viscosity of carbonaceous mixtures and to reduce the amount of binder ordinarily required in obtaining a product having improved physical and mechanical properties; and a still further object is to provide a rapid and eificient method for extruding carbonaceous mixtures which can be easily graphitized, to produce a commercially satisfactory low-resistance product.

In accordance with the invention, green carbonaceous material is prepared by mixing some form of carbon, a binder such as coal-tar pitch, and about 1% to 4% by weight of a selected organic lubricant. 'I he carbonaceous mixture is extruded to the desired shape, which may then be baked and subsequently 'graphitized. While the action of the lubricant is definite, the exact manner in which it serves is not fully understood. Certainly, the lubricant of the invention lowers the viscosity of mixture and thus reduces the pressures required in the extrusion process. In a sense, the lubricant may serve as a bearing material between the abrasive filler particles and the relatively viscous binder, to provide intimate mixing of the two principal phases of the carbon mix system and thus promote the formation of intimately bound particles. The lubricant may also serve to enhance filler particle-binder homogeneity, in that each filler particle becomes coated uniformly with the binder without reacting or solubilizing it; the binder thus retains its original adhesive characteristics and contributes toward a maximization of final graphite properties. It is believed that the selective lubricant causes the filler particles, which are irregular in form, to rearrange with their long axes parallel -to the direction of extrusion; in other words, the particles are aligned as ice they are extruded, to form intimately bound extruded articles. Fortunately, the lubricant appears to be immiscible in thebinder so as not to interefere with the chemical or physical structure of the binder.

The lubricant of the present invention is readily carbonized or graphitized Without leaving an undesirable contaminant in the extruded or graphitized article. Moreover, during the extrusion process, the lubricant tends to be forced from an inter-particulate association toward the periphery of the extruded shape, to minimize contaminatin-g effects therein and to desirably increase lubricity at the interface of extrusion die and extruded shape. The intimate mixing provided by the lubricant reduces the amount of binder required; fortunately, as the amount of binder is decreased, the density of either green or baked carbonaceous mix is advantageously increased, while the loss of weight ordinarily occurring in the baking period is decreased.

I have found that certain organic lubricants have a very specific action in promoting the formation of intimately bound and homogeneous extruded shapes, at favorable pressures and temperatures, in the manner described above. These lubricants are stearamide,

( rr ss z) laurarnide, (C H C'ONH 1,26-hex-acosanediamide, (ethylene dilauramide, [CH C H CONH and 6,20-hexacosadiene-1,26-dianride, (ethylene di-sym. dodecyleneamide, [-CH (CH CH :CH (CH 00N11 both of which are diamides of lauric acid; and l,3'8-octat riacontanediamide (ethylene distearamide,

and 9,29-octatriacontadiene-1,3S-diamide (ethylene diolamide, [-CH (CH CH:CH(C-H CONH both of which are diamides of stearic acid.

In carrying out a process of the invention, the carbonaceous mixture is made by initially mixing a carbon filler such as petroleum coke and coal-tar pitch at ordinary temperatures followed by mixing at elevated temperatures. The extrusion lubricant is added to the mix, in an amount equal to from about 1% to 4% by weight of the total filler and binder, during the last few minutes of mixing. After cooling, this mixture is reduced by crushing and screening operations to particles of a fineness sufficient to pass through a 20 mesh Tyler standard sieve or screen. The powder is extruded at selective temperatures and extrusion pressures to form green rods or electrodes, so designated as to distinguish them from the finished and baked article. The green product is heattreated at temperatures ranging from 800 C. to 1400 C., whereby the coal-tar pitch loses its lighter constituents by distillation and is finally converted into coke, and the carbon filler loses any volatile matter or contaminants it may have retained during its formation. As a result, the entire mass of the baked product is intimately bound and held together strongly, each small filler particle that had been previously covered by a binder film is now bound to adjacent particles by an extremely thin layer of carbon. The lubricant of the invention is converted to carbon within the baked product Without leaving any residual contaminant. The baked rods may be graphitized by heating them to temperatures Within the range between 2000 C. and 3000 C., at which time the carbon crystallizes in the rod are converted to graphite crystals and the lubricant is converted to graphite and retained within the finished product.

The following examples will serve only to illustrate the invention more fully, and accordingly they are not to be construed as limiting the scope of the invention.

Example 1 A typical carbonaceous mix was prepared, containing the following ingredients: 38.5% petroleum coke particles, which pass througha 35 mesh screen but are retained on a 65 mesh screen; 38.5 petroleum coke flour which passes through a 200 mesh screen; and 23% binder comprising a medium coal-tar pitch. The mix was made by initially blending the above ingredients in a blender for a period of 5 minutes and then mixing in a conventional mixer for thirty minutes at 140l45 C. The extru sion lubricant was added to the mix, in an amount equal to 2% of the total filler and binder during the last five minutes of mixing. The mix, after cooling, was reduced by jaw-crushing and screening ,proceduresto a powder of a size less than 20 mesh: The powder was then extruded in a conventional vertical press. For simplicity, the details as to melting points, cylinder temperatures, die temperature, extrusion pressures, and run-out speeds are indicated in Table I below:

TABLE I.'EXTRUSION DATA Melting Cylinder Die Extrusion Run-out Lubricant Point, Temp, Temp., Pressure Speed 0. 0. C. (p.s.i.) (in/min.)

Stearamide 105-107 135-140 50 1,200 6-8 1,38-Octatriacontanediamide 140-142 135-140 45 850 8 9,29-Octatriacontadiene1,38- diainide 119-121 135-140 50 1,250 6 The green rods of the above examples were measured for both density and tested for carbon flexural strength. The green and baked densities, volume change obtained in baking, and baked fiexural strengths are listed in Table 11 below:

TABLE II.PROIERTIES OF SPECIMENS FROM LUBRI- OATED MIXES 1 Volume Baked Standard Lubricant Density (G./cc.) Change Flexural Deviation Green Baked (pen Strength (p.s.i.)

cent) (p.s.i.)

Stearamide 1.79 1.62 +0. 95 3,570 5:308 1,38-Octatriacontanediamide 1.80 1.59 +2.35 2,986 i281 9,29 Octatriacontadiene-1,38-diamide 1.79 1.63 +0. 90 3,728 i307 1 All entries are averages of eight or more sample measurements, which incidentally accounts for listing of the standard deviation values in this table The data in Table I discloses that all three amidic compounds are good extrusion lubricants. When die temperature, extrusion pressure, and run-out speed are considered collectively, 1,38octatriacontanediamide appears to have significant superiority; on the other hand, the data in Table II shows that use of this lubricant results in a product which is somewhat inferior in strength and density when compared to products obtained using the other two lubricants. However, none of the differences in density -or volume change given in Table II are actually statisti- The preceding examples disclose the use of three amidic lubricants: a paraflinic amide containing 18 carbon atoms; a paraffinic diamide containing 38 carbon atoms; and an olefinic diamide containing 38 carbon atoms. Three other arnidic lubricants that are readily obvious and suitable for purposes of the present invention are lauramide, 1,26-hexacosanediamide, and 6,20-hexacosadiene-1,26 diamide, the latter two being homologs of 1,28-octatriacontanediamide and 9,29-octatriacontadiene-1,38-diamide, respectively. The diamides containing 26 carbon atoms have lower melting points than their corresponding homologs, and consequently their use in the practice of the present invention lowers the required extrusion pressures, as indicated above.

Additional experiments were conducted on compounds similar to the amidic lubricants of the invention. It was found that paraflin oil and organic amides or organic amines of small molecular size, such as ethylenediamide and acetamide, were ineffective as extrusion lubricants. In the case of ethylenediamine and acetamide, it was not possible to extrude the carbonaceous mix, even though the extrusion pressure was raised to 2100 p.s.i. In the case of paratfin oil, a run-out speed of 2 in./min. was realized, which is commercially unsatisfactory. These results would seem to indicate that length of molecular chain is influential in producing maximum lubricity [for carbon extrusion; long chain organic amides containing in the order of 12 to 52 carbon atoms provide the desired lubricity, while relatively short chain organic compounds are unsatisfactory -for such purpose. Suitable long chain organic amides of the type contemplated include, but are not limited to, lauramide (C H -CO-NH already referred to, and also ethylene dihyenamide and stearanilide (C17H35CO 'NHC6H5) The invention is not limited to the specific embodiments described herein, but may be practiced in other ways without departing from the spirit and scope of the invention as defined by the following claims.

I claim:

1. A carbonaceous mixture for electrodes and the like having improved extrusion properties consisting essentially of a carbonaceous filler material a coal-tar pitch binder and from about 1% to about 4% amide containing from 12 to 52 carbon atoms.

2. A carbonaceous mixture according to claim 1 in which the organic amide is selected from the group consisting of stearamide, lauramide, ethylene di-launamide, ethylene di-symmetrical, dodecylenamide, ethylene distearamide, and ethylene dioleamide.

3.- A carbonaceous mixture according to claim 1 in which the organic' amide is steararnide.

4. A carbonaceous mixture according to claim 1 in which the organic amide is ethylene distearamide.

5. A carbonaceous mixture according to claim 1 in which the organic amide is ethylene diolcamide.

6. A carbonaceous mixture according to claim 1 characterized by said carbonaceous filler material being selected from the group of petroleum coke, pitch coke, graphite flour, and carbon black.

7. A carbonaceous mixture according to claim 2, characterized by said carbonaceous filler material being selected [from the group of petroleum coke, pitch coke, graphite flour, and carbon black.

8. A method for improving the extruison properties of a carbonaceous composition for electrodes and the like consisting essentially of a carbonaceous filler and coal tar pitch binder, comprising the addition to said carbonaceous composition from about 1% to about 4% by weight of an organic amide lubricant containing from 12 to 52 car. bon atoms.

9 method according to claim 8 in which the organic amide is selected from the group consisting of steararnide,

by weight of an organic 5 5 l auramide, ethylene dilaurarnide, ethylene (ii-symmetrical 2,929,108 3/ 1960 Sands 264- 105 dodecylenamide, ethylene distearamide, and ethylene di- 2,980,516 4/1961 Croy 252-5 10 X FOREIGN PATENTS References Cited by the Examiner 5 202,236 5/1956 Austmlia UNITED STATES PATENTS 617,466 2/ 1949 Great Britain.

1,649,545 11/1927 Renou 106--284 2,500,208 3/1950 Shea ,106 284 ALEXANDER H. BRODMERKEL,Pnmary Examzner.

2,500,209 3/ 1950 Shea 264105 R. B. MOFFITT, I. B. EVANS, AssistantExaminers.

Claims

1. A CARBONACEOUS MIXTURE FOR ELECTRODES AND THE LIKE HAVING IMPROVED EXTRUSION PROPERTIES CONSISTING ESSENTIALLY OF A CARBONACEOUS FILLER MATERIAL A COAL-TAR PITCH BINDER AND FROM ABOUT 1% TO ABOUT 4% BY WEIGHT OF AN ORGANIC AMIDE CONTAINING FROM 12 TO 52 CARBON ATOMS.