US2640787A - Manufacture of carbonaceous molding compositions - Google Patents

Description

Patented June 2, 1953 MANUFACTURE OF oARBoN cEo s MOLDING COMPOSITIONS Charles Desmond 'Greaves and William Duncan Parker, London, England, assignors to C. D. Patents Limited, London, England, a British company No Drawing. Application October 11, 1948, Serial No. 53,992. In Great Britain October 15, 1947 4 Claims. (Cl. 106-285) This invention relates to improvements in the manufacture of carbonaceous moulding compositions suitable for extrusion.

There is a wide variety of articles which can with advantage be shaped by extrusion; these include rods, bars, tubes or pipes of rectangular, polygonal, circular or elliptical section or of more complex shapes. It is highly desirable to produce as final products moulded carbon articles which have been fired and which are strong, tough, resistant to solvents to acids or to alkalies, which can stand high temperatures and are free from bubbles or from visible porosity. For the manufacture of carbon articles the dry powdermoulding technique, such for example as that described in United States patent application Serial No. 622,934, now Patent No. 2,461,365 has certain advantages. One of these advantages is the ability to fire the moulded shapes at relatively rapid rates of temperature rise without causing intumescence. At the same time the moulding of dry powders imposes limitations on the shapes that can be produced. One object of this invention is to produce from coal a composition which may conveniently be moulded by extrusion. Another object is to produce such a composition which, after moulding, may be heated rapidly without intumescence taking place. A further object is to produce from such a composition strong, tough, moulded carbon articles which are of simple or of complex shape.

According to the present invention, a method of making a carbonaceous moulding composition, especially an extrusible composition, consists in mixing at an elevated temperature subdivided coal and a softening agent as hereinafter defined. The coals suitable for use in this invention are those having up to 25% volatile matter on the dry ash-free basis, preferably between 6% and 20%. The particle size of the sub-divided coal may be about 80 to 150 mesh British Standard sieve, but gradings of coarser and finer particles may be employed according to the type of moulded product it is desired to make.

A suitable temperature for the mixing operation is from 60-180 C. -It is advantageous to digest the mixture for a considerable period, say 4-8 hours.

The expression softening agent used herein:

means a material which exercises a solvent action upon the coal and comprises at least one of the following: 'Coal tar middle oil, coal tar heavy oil, coal tar anthracene oil, coal tar pitch (including specially treated pitches which are neutral); aromatic compounds which are hydrocarbons or derivatives of benzene, naphthalene, an-

thracene, phenanthrene or like aromatic hydrocarbons, such derivatives including phthalic acidesters, aryl esters of phosphoric acid; naphthenic and heterocyclic compounds; petroleum residues, soft bitumen; and chlorinated paraffin waxes.

The proportion of softening agent may conveniently be from 10% to 30% by weight of the mixture. In order to reduce the consistency of the moulding composition or dough there may be added to the mixture after cooling a light oil such, for example, as a solvent naphtha.

The mixing at an elevated temperature of the coal powder and softening agent produces a reaction on the coal which appreciably increases the swelling properties of the mixture above that of the coal used, and in the case of non-agglutinating coals allows a strong, coherent product to be made by subsequent moulding and heating. It is a feature of this invention that such products can be made from non-agglutinating coals of anthracite and semi-anthracite character.

However such non-agglutinating coals may be .blended with coals of more agglutinating or of by adding to the mixture an oxidizing or dehy-. drogen-ating agent, the rate of heating of the' resultant composition after moulding may be.

substantially equal to the rate at which the coal alone could have been heated without intumescence taking place e. g. 1 C. to 2 C. per minute.

a The dehydrogenating agent, for example sulphur or selenium or nitrobenzene, must be of such a softening agent the r 3 character and must be 'added in such a manner (e. g. after cooling of the mixture) that it does not react with the mixture to a significant extent, and hence does not harden the mixture, until after moulding has been completed.

Accordingly, the invention includes a method of making a carbonaceous moulding composition, especially an extrusible composition, which method consists in mixing at an elevated temperature subdivided coal and a softening agent as hereinbef'ore defined and adding tothe mixture after 'it' has cooled an oxidizing ordehydrogenating agent such as sulphur, or selenium or such as nitrobenzene.

To avoid a reaction which would impairthe" moulding properties of the compositicmthemixture should be cooled to a temperature below that at which as experimentally determined-{reaction between the particular agentnused and 'a particular mixture takes place. The addition of the dehydrogenating agent may be made in any suitable mixing machine. important.

If desired there may also be added tothe mixture a swell inhibitor such for example as finely subdivided natural graphite which contributes to the flow properties of'the composition.

In order to manufacture strong,,useful' moulded products it isinecessary to submit thecompos'ition to a shaping and. to 3.; heating operation. The invention includes, therefore,- amethod of making a moulded carbon product which method'consists in. submitting" a composition made as above-described to a mouldingor shaping operation and heating the shaped article under" non -oxidizing conditions to a'temperature' of; atleast 550 C., and preferably above 700 C.

A preferred technique" is to cool the digested mixture, to form" a'solid' billet' under mechanical pressure whilst simultaneously "extracting air from the cylinder-or containerwithinwhich the billet is formed so that thebilletcontains no bubbles, then to put the'bil'let into theextrusion press. If an'ad'ded' agent such-as sulphur-is present extrusion is 'bestefiectedatroom tempera-' ture, 'butwith other-agents (and'even w'i'th=sulphur) extrusion can be effected inthewarm.

Example I 300gm. of a S'QWal'es semi anthracite coal (2.3% ash and 7.8%" volatile matteron the dry ash-free basis) "which had" been ground to pass 95%" through a 200me'sh B: S: sieve were mixed with 100 gm. of No. 2 anthracene oil in a-dough mixer (Z=blademixer)"at"a tempera-ture f'1'60- C.-180 C. 'After' hours" digestion'had elapsed the mixture was allowed to cool to belowi? C. whereupon 45 mlxof' solvent naphtha were added and mixing continued fora further hour. The

composition was then removed'from the mixing- Example II 300 gm. of 21:8. Wales carbonaceous coal (3.1% ash and 17.11% volatile-matter 'on the dry ash- Intimate admixture is .4 free basis) which had been ground to pass through a 200 mesh B. S. sieve were mixed with 50 gm. of No. 2 anthracene oil and 50 gm. solvent naphtha in a Z-blade mixer at a temperature of -110 C. After 2 hours digestion had elapsed the mixture was allowed to cool to about 30 C. and a mixture consisting of 50 gm., of finely divided natural graphite, 12 gm. of sulphur (dehydrogenating agent) and 25 gm. of solvent naphtha was added and mixing was continued for-a. further 1'" hour. The: composition was removed fromthe-mixing machine and-was extruded and heated in the manner described in Example I except that the rate of temperature 15.

riseinthe heating operation was 1 C. per minute. "It.-=utillhbe understood that if it be desired to produce products of very low porosity, the heatsubstantial proportion of a readily-decomposable hydrocarbon gas'su'c'h as ethylene.

Alli-the swelling .rnumber determinations redenied-to herein are. by the method described in British. Standard 1016.

We-claim:

1. A process for the manufacture of a doughlike extrusibl'e-composition consisting mainly-of coal from non-bitmnincus, non-agglutina'ting coal, which process comprises mixing th coal, 95% (if-which passes a 200" mesh-sieve, with a relatively high boiling softening agent in the amount of 10 to 30 by weight'of the mixture, heating the mixture to a temperature between 60 C. and 180 C., digestingthe 'mixturewith continued mixing for between 2 and-8 hours;al'- lowing the mixture to cool and thereafter adding and mixing a solvent having a lowerboiling p0inl3 than said softening'agent to reduce the consistency of said mixture, whichsolvent' is non-reactive with the-aforesaid mixture-and is present inaweight less than that of the softening agent.

"2;;A'process'for the manufacture. of a doughlike extrusible composition consisting mainly of coal. from non-bituminous, 'non agglutinating 009.1, which. process comprises mixing the coal, 95% "of'which passes"'a"200 mesh sieve, with a relatively "high boiling softening agent in'the amolmt of'10%' to 30% by weight of the mixture anda solvent having alower' boiling point than said softening agent for the softening agent, which'so-lvent' is 'non-reactive'with the mixture and is added a proportion by weight of the coal substantiallythe same as the proportion of. softening agent, heating the mixture to a temperature of"60 C. to 180 C.,and continuing mixing the heated mixture for between 2 and 8 hours.

3. A process for-themanufacture of a doughlike *extrusible' composition consisting mainly of coal from non-bituminous, non-agglutinating coal having about 8%volatile matter on a dry ash-free-'-basis,"which process comprises mixing thecoal, 95% of which passes through a 200 mesh sieve, with =anthracene oil in an amount about 25% by weight of the mixture, said mixing being carriedout at a temperature of C. to C. for aperiod of about' l hours; and thereafter'a'llowing the mixture to cool to below100 C. and then adding and mixing for about ,4; hour solvent naphtha in an amount by weight-about half that of the-anthracene oil.

'4. "A process for the manufacture of a doughlike extrusible composition consisting mainlyof coal from non-bituminous, non-agglutinating coal having about 17% volatile matter on a dry a'sl'x-free-basis, which process comprises mixing 6 References Cited in the file of this patent UNITED STATES PATENTS- Number Name Date Pierre Apr. 5, 1864 Van Brunt Feb. 13, 1912 Hite May 1, 1917 Thomsen Oct. 16, 1917 Myler Oct. 27, 1925 Hill Sept. 6, 1932 Kemmer July 27, 1937 Reuscher Feb. 21, 1939 Thrune Jan. 13, 1942 Fair Feb. 19, 1946- Fair Mar. 19, 1946 Bangham et al. July 16, 1946 Bennett et a1 Jan. 3, 1950

Claims (1)

1. A PROCESS FOR THE MANUFACTURE OF A DOUGHLIKE EXTRUSIBLE COMPOSITION CONSISTING MAINLY OF COAL FROM NON-BITUMINOUS, NON-AGGLUTINATING COAL, WHICH PROCESS COMPRISES MIXING THE COAL, 95% OF WHICH PASSES A 200 MESH SIEVE, WITH A RELATIVELY HIGH BOILING SOFTENING AGENT IN THE AMOUNT OF 10% TO 30% BY WEIGHT OF THE MIXTURE, HEATING THE MIXTURE TO A TEMPERATURE BETWEEN 60* C. AND 180* C., DIGESTING THE MIXTURE WITH CONTINUED MIXING FOR BETWEEN 2 AND 8 HOURS, ALLOWING THE MIXTURE TO COOL AND THEREAFTER ADDING AND MIXING A SOLVENT HAVING A LOWER BOILING POINT THAN SAID SOFTENING AGENT TO REDUCE THE CONSISTENCY OF SAID MIXTURE, WHICH SOLVENT IS NON-REACTIVE WITH THE AFORESAID MIXTURE AND IS PRESENT IN A WEIGHT LESS THAN THAT OF THE SOFTENING AGENT.