Patent US3976746A successfully refreshed from Google Patents.
US3976746A
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Graphitic fibers having superior composite properties and methods of making same
Assignee: BP Chemicals Hitco Inc
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Filing: 1974-06-06
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Granted: 1976-08-24
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Expires: 1994-06-06
Abstract
Abstract At least partially carbonized fibers formed by pyrolysis from precursor fibers are converted to graphitic fibers in successive heating and stretching zones in which a transitional phase of high fiber reactivity is utilized. Chemical agents applied to the fibers during this transition increase matrix-fiber adhesion properties by reacting with the fibers before they develop excessive levels of crystallographic order and become inert at graphitization temperature levels. Improved control of fiber properties is achieved by employment of short residence times and resistive heating with concurrent stretching in the zones, and by imparting high stretch levels at relatively low temperatures to the fibers. The resultant fibers have superior properties for component structures and at the same time have excellent tenacity and modulus values as well.
Inventors
- 👤 Irvin Wizon
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:24
CPC Classifications
D; D01; D01F; D01F9/00; D01F9/08; D01F9/12; D01F9/14; D01F9/16
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
128 words
A method of substantially graphitizing carbon material while maintaining a relatively high degree of reactivity in the material comprising the steps of: subjecting carbonaceous fibrous material which is initially of at least partially carbon composition to a plurality of successive treatments until the material is of substantially graphitic composition, said treatments comprising heating the material to a selected substantially fixed temperature less than 1900° C. in the first treatment and higher than the temperature of preceding treatments in subsequent treatments and concurrently stretching the material relative to the starting length; and reacting the material during or before one of said treatments with a reactive agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid.
Claim 2
Independent Claim
128 words
A method of substantially graphitizing carbon material while maintaining a relatively high degree of reactivity in the material comprising the steps of: subjecting carbonaceous fibrous material which is initially of at least partially carbon composition to a plurality of successive treatments until the material is of substantially graphitic composition, said treatments comprising heating the material to a selected substantially fixed temperature less than 1900° C. in the first treatment and higher than the temperature of preceding treatments in subsequent treatments and concurrently stretching the material relative to the starting length; and reacting the material during or before one of said treatments with a reactive agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid.
Claim 3
Dependent Claim
34 words
The method of claim 1, wherein each of said treatments is performed in a different zone of elevated temperature and the material is exposed to the reactive agent before entering one of the zones.
Claim 4
Dependent Claim
49 words
The method of claim 1, wherein each of said treatments is performed in a different zone of elevated temperature, and the material is immersed in the reactive agent in liquid form prior to entry into at least one of the zones, the reagent volatilizing in the immediately subsequent zone.
Claim 5
Dependent Claim
87 words
A process for graphitizing carbonaceous fibers comprising the steps of successively heating and concurrently stretching the fibers in each of a plurality of different treatment zones of successively higher temperature to produce substantially graphitic fibers, reacting the fibers with a reactive agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid in at least one of the zones, the temperature in the last of the zones being held at less than 2800° C.
Claim 6
Dependent Claim
87 words
A process for graphitizing carbonaceous fibers comprising the steps of successively heating and concurrently stretching the fibers in each of a plurality of different treatment zones of successively higher temperature to produce substantially graphitic fibers, reacting the fibers with a reactive agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid in at least one of the zones, the temperature in the last of the zones being held at less than 2800° C.
Claim 7
Dependent Claim
107 words
In a process for graphitizing carbon fibers in which the fibers are heated in a first zone to a temperature less than 1900° C., and concurrently stretched, and thereafter heated in at least a second zone to a temperature greater than the temperature in the first zone and less than 2800° C., and concurrently stretched, to produce substantially graphitic fibers, the improvement comprising the step of applying a reactive agent to the fibers in at least one of the zones, the reactive agent being selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid.
Claim 8
Dependent Claim
107 words
In a process for graphitizing carbon fibers in which the fibers are heated in a first zone to a temperature less than 1900° C., and concurrently stretched, and thereafter heated in at least a second zone to a temperature greater than the temperature in the first zone and less than 2800° C., and concurrently stretched, to produce substantially graphitic fibers, the improvement comprising the step of applying a reactive agent to the fibers in at least one of the zones, the reactive agent being selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid.
Claim 9
Dependent Claim
22 words
The invention defined in claim 5, wherein the step of applying a reactive agent to the fibers occurs in the second zone.
Claim 10
Dependent Claim
38 words
The invention defined in claim 5, wherein the step of applying a reactive agent to the fibers comprises immersing the fibers in the reactive agent in liquid form prior to entry of the fibers into the second zone.
Claim 11
Independent Claim
160 words
The method of preparing graphitic fibers having substantial tensile and modulus values and improved composite properties from partially carbonized fibers comprising the steps of: heating the fibers at a substantially fixed first temperature above the temperature at which the fibers will stretch and less than 1900° C. for a time no greater than approximately 5 seconds; concurrently stretching the fibers in excess of approximately 15% of their original length; applying a liquid reagent to the fibers, the reagent being selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid; heating the fibers at a substantially fixed second temperature high enough to volatilize the liquid reagent and less than 2800° C. for a time no greater than approximately 1 second while concurrently developing a desired degree of graphiticity within the fibers; and concurrently stretching the fibers in excess of 10% of their length prior to the second stretching.
Claim 12
Independent Claim
160 words
The method of preparing graphitic fibers having substantial tensile and modulus values and improved composite properties from partially carbonized fibers comprising the steps of: heating the fibers at a substantially fixed first temperature above the temperature at which the fibers will stretch and less than 1900° C. for a time no greater than approximately 5 seconds; concurrently stretching the fibers in excess of approximately 15% of their original length; applying a liquid reagent to the fibers, the reagent being selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid; heating the fibers at a substantially fixed second temperature high enough to volatilize the liquid reagent and less than 2800° C. for a time no greater than approximately 1 second while concurrently developing a desired degree of graphiticity within the fibers; and concurrently stretching the fibers in excess of 10% of their length prior to the second stretching.
Claim 13
Dependent Claim
27 words
The method as set forth in claim 8 above, wherein the fibers are yarn of cellulosic origin and the heating is resistive heating in a continuous sequence.
Claim 14
Dependent Claim
50 words
The method as set forth in claim 8 above, wherein the reagent volatilizes in the second zone, and wherein the method further includes the step of maintaining a positive pressure of inert gas at the fibers during the steps of heating and concurrently stretching to prevent the introduction of air.
Claim 15
Dependent Claim
39 words
The method as set forth in claim 9 above, wherein the first temperature is approximately 1830° C. and the first stretch is approximately 20%, and the second temperature is approximately 2730° C. and the second stretch is approximately 15%.
Claim 16
Dependent Claim
40 words
The method as set forth in claim 8 above, wherein the liquid reagent comprises an aqueous solution and the method includes the step of continuously moving the fibers through the liquid reagent and through the successive heating and stretching steps.
Claim 17
Dependent Claim
16 words
The method as set forth in claim 8 above, wherein the liquid reagent comprises cobalt sulfate.
Claim 18
Dependent Claim
16 words
The method as set forth in claim 8 above, wherein the liquid reagent comprises potassium dichromate.
Claim 19
Dependent Claim
27 words
The method as set forth in claim 12 above, wherein the aqueous solution has a concentration of liquid reagent in the range of about 0.15% to 0.3%.
Claim 20
Independent Claim
136 words
The method of treating partially carbonized fibers having 75-80% carbon to derive graphitic fibers comprising the steps of: resistively heating a moving short span of the fibers at a first fixed temperature level below approximately 1900° C. for no greater than approximately 5 seconds; concurrently stretching the fibers in excess of 15% of their length; treating the fibers with an agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid; resistively heating a moving short span of the treated fibers at a second fixed temperature level greater than the first fixed temperature level and below approximately 2800° C. for no greater than approximately 2 seconds to produce substantially graphitic fibers; and concurrently stretching the fibers in excess of 10% of their length.
Claim 21
Independent Claim
136 words
The method of treating partially carbonized fibers having 75-80% carbon to derive graphitic fibers comprising the steps of: resistively heating a moving short span of the fibers at a first fixed temperature level below approximately 1900° C. for no greater than approximately 5 seconds; concurrently stretching the fibers in excess of 15% of their length; treating the fibers with an agent selected from the group consisting of potassium carbonate, cobalt sulfate, a mixture of nickel nitrate and sodium hypochlorite, potassium dichromate and oxalic acid; resistively heating a moving short span of the treated fibers at a second fixed temperature level greater than the first fixed temperature level and below approximately 2800° C. for no greater than approximately 2 seconds to produce substantially graphitic fibers; and concurrently stretching the fibers in excess of 10% of their length.
Claim 22
Dependent Claim
33 words
The method as set forth in claim 16 above, wherein the short spans of the fibers are approximately 8 inches or less and approximately 1.5 inches or less in the successive heating steps.
Claim 23
Dependent Claim
20 words
The method as set forth in claim 17 above, wherein the fibers have been partially carbonized to approximately 400° C.
Claim 24
Dependent Claim
55 words
The method as set forth in claim 24 above, wherein the fibers are in yarn form and are continuously passed through the successive steps, and the step of treating the fibers with an agent comprises immersing the yarn in the reagent in liquid form between successive heatings and volatilizing the reagent during the subsequent heating.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-24 | 1980-02-23 | 1980-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-24 | 1984-02-23 | 1984-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-24 | 1988-02-23 | 1988-08-24 | $7700.00 | Window Closed / Lapsed |