Process for making graphite articles
View Patent ↗A process for preparing graphite articles is presented. In particular, the process includes employing a particulate fraction comprising at least about 35 weight percent coke, coal or combinations thereof having a diameter such that a major fraction of it passes through a 0.25 mm to 25 mm mesh screen. The particulate fraction is mixed with a liquid or solid pitch binder, to form a stock blend; the stock blend is extruded to form a green stock; the green stock is baked to form a carbonized stock; and the carbonized stock is graphitized. The stock blend further includes carbon fibers added after mixing of the particulate fraction and pitch has begun.
1. A process for preparing a graphite article, the process comprising
(a) mixing (i) a particulate fraction comprising at least about 35 weight percent coke, coal or mixtures thereof having a diameter such that a major fraction passes through a 25 mm mesh screen but not a 0.25 mm mesh screen, (ii) a pitch binder and (iii) carbon fibers, to form a stock blend;
(b) extruding the stock blend to form a green stock;
(c) baking the green stock to form a carbonized stock; and
(d) graphitizing the carbonized stock by maintaining the carbonized stock at a temperature of at least about 2500° C.,
wherein the fibers are added to the particulate fraction and pitch binder after at least about 15% of the mix cycle is completed.
2. The process of claim 1 wherein the fibers have an average length of no more than about 32 mm.
3. The process of claim 1 wherein the fibers are added to the particulate fraction and pitch binder after at least about 50% of the mix cycle is completed.
4. The process of claim 1 wherein the carbon fibers are present at a level of about 0.5 to about 6 parts by weight of carbon fibers per 100 parts by weight of calcined coke.
5. The process of claim 4 wherein the carbon fibers have a tensile strength of at least about 150,000 psi.
6. The process of claim 4 wherein the carbon fibers have a Young's modulus of about 15×10 6 psi.
7. The process of claim 4 wherein the carbon fibers have an average diameter of about 6 microns to about 15 microns.
8. The process of claim 1 wherein the particulate fraction comprises materials selected from the group consisting of calcined coke, petroleum coke, coal derived coke, calcined anthracite coal or mixtures thereof.
9. The process of claim 1 wherein the particulate fraction comprises up to about 65% of a filler comprising at least about 75% coke having a diameter such that at least about 70% will pass through a 200 Tyler mesh screen.
10. The process of claim 9 wherein the coke in the filler has a diameter such that at least about 90% will pass through a 200 Tyler mesh screen.
11. The process of claim 9 wherein the filler comprises between about 0.5% and about 25% of additives.
12. The process of claim 11 wherein the additives comprise iron oxide having an average particle diameter such that they are smaller than about 10 microns, petroleum coke having an average particle diameter such that they are smaller than about 10 microns, and combinations thereof.
13. The process of claim 1 wherein the particulate fraction comprises at least about 50 weight percent coke, coal or mixtures thereof having a diameter such that a major fraction passes through a 25 mm mesh screen but not a 0.25 mm mesh screen.