Process for the production of large denier carbon fibers

Claim 2

AN IMPROVED PROCESS FOR THE FORMATION OF A LARGE DENIER CARBONACEOUS FIBROUS MATERIAL COMPRISING: A. CONTACTING A POLYBENZIMDAZOLE FIBROUS MATERIAL HAVING A DENIER PER FILAMENT OF ABOUT 50 TO600 WITH A SOLUTION OF AN ACID HAVING A PK4 VALUE BELOW ABOUT 4.5 WHILE AT AN ELEVATED TEMPERATURE TO TRANSFORM SAID POLYBENZIMIDZOLE TO A POLYBENZIMIDAZONIUM SALT WHERIN THE ANION OF SAID SALT IS DERIVED FROM SAID ACID, B. HEATING SAID FIBROUUS MATERIAL FOLLOWING CONTACT WITH SAID ACID IN AN OXYGEN-CONTAINING GASEOUS ATMOSPHERE AT A TEMPERATURE AT ABOUT 300* TO 530*C. TO RENDER SAID FIBROUS MATERIAL CAPABLE OF UNDERGOING CARBONIZATION WHILE RETAINING THE ORIGINAL FIBROUS CONFIGURATION SUBSTANTIALLY INTACT, AND C. HEATING SAID RESULTING FIBROUS MATERIAL IN A NON-OXIDIZING GASEOUS ATMOSPHERE AT A TEMPERATURE OF AT LEAST 1000*C. UNTIL A CARBONACEOUS FIBROUS MATERIAL IS FORMED WHICH CONTAINS AT LEAST 90 PERCENT CARBON BY WEIGHT AND RETAINS THE ORGINAL FIBROUS CONFIGURATION SUBSTANTIALLY INTACT.

Claim 3

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said polybenzimidazole fibrous material consists essentially of recurring units of the formula:

Claim 4

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said polybenzimidazole fibrous material is poly-2,2''-(m-phenylene)-5,5''-bibenzimidazole.

Claim 5

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said polybenzimidazole fibrous material has denier per filament of about 100 to 500.

Claim 6

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said acid is selected from the group consisting essentially of sulfamic acid, phosphoric acid, sulfuric acid, hydrochloric acid, and acetic acid.

Claim 7

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said solution of said acid utilized in step (a) is provided at a temperature of about 50* to 100*C. when contacted with said fibrous material.

Claim 8

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 6 wherein said contact is conducted for about 2 to 50 minutes.

Claim 9

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said oxygen-containing gaseous atmosphere is air.

Claim 10

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said fibrous material following contact with said acid is heated in said oxygen-containing atmosphere of step (b) for about 1 to 30 minutes.

Claim 11

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said non-oxidizing gaseous atmosphere of step (c) is selected from the group consisting essentially of nitrogen, argon, and helium.

Claim 12

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 1 wherein said resulting fibrous material is heated in said non-oxidizing gaseous atmosphere of step (c) for about 2 to 20 minutes.

Claim 13

An improved process for the formation of a large denier carbonaceous fibrous material comprising: a. contacting a poly-2,2''-(m-phenylene)-5,5''-bibenzimidazole fibrous material having a denier per filament of about 100 to 500 with an aqueous solution of an acid selected from the group consisting essentially of sulfamic acid, phosphoric acid, sulfuric acid, hydrochloric acid and acetic acid, while at a temperature of about 50* to 100*C. for a residence time of about 2 to 50 minutes to transform said poly-2,2''-(m-phenylene)-5,5''-bibenzimidazole to a polybenzimidazonium salt wherein the anion of said salt is derived from said acid, b. heating said resulting fibrous material following contact with said acid in an oxygen-containing gaseous atmosphere at a temperature of about 300* to 530*C. for a residence time of about 1 to 30 minutes to render said fibrous material capable of undergoing carbonization while retaining the original fibrous configuration substantially intact, and c. heating said resulting fibrous material at a temperature of at least 1000*C. in a non-oxidizing gaseous atmosphere selected from the group consisting essentially of nitrogen, argon, and helium for a residence time of about 2 to 20 minutes until a carbonaceous fibrous material is formed which contains at least 90 percent carbon by weight and retains the original fibrous configuration substantially intacT.

Claim 14

An improved process for the formation of a large denier carbonaceous fibrous material comprising: a. contacting a poly-2,2''-(m-phenylene)-5,5''-bibenzimidazole fibrous material having a denier per filament of about 100 to 500 with an aqueous solution of an acid selected from the group consisting essentially of sulfamic acid, phosphoric acid, sulfuric acid, hydrochloric acid and acetic acid, while at a temperature of about 50* to 100*C. for a residence time of about 2 to 50 minutes to transform said poly-2,2''-(m-phenylene)-5,5''-bibenzimidazole to a polybenzimidazonium salt wherein the anion of said salt is derived from said acid, b. heating said resulting fibrous material following contact with said acid in an oxygen-containing gaseous atmosphere at a temperature of about 300* to 530*C. for a residence time of about 1 to 30 minutes to render said fibrous material capable of undergoing carbonization while retaining the original fibrous configuration substantially intact, and c. heating said resulting fibrous material at a temperature of at least 1000*C. in a non-oxidizing gaseous atmosphere selected from the group consisting essentially of nitrogen, argon, and helium for a residence time of about 2 to 20 minutes until a carbonaceous fibrous material is formed which contains at least 90 percent carbon by weight and retains the original fibrous configuration substantially intacT.

Claim 15

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 12 wherein said fibrous material is a continuous length of a multifilament yarn.

Claim 16

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 12 wherein said fibrous material is a continuous length of a multifilament tow.

Claim 17

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 12 wherein said aqueous solution of said acid additionally includes a swelling agent for said fibrous material.

Claim 18

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 15 wherein said swelling agent is benzyl alcohol.

Claim 19

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 15 wherein said oxygen-containing gaseous atmosphere of step (b) is air.

Claim 20

An improved process for the formation of a large denier carbonaceous fibrous material in accordance with claim 15 wherein said non-oxidizing gaseous atmosphere of step (c) is nitrogen.