US4073869A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Internal chemical modification of carbon fibers to yield a product of reduced electrical conductivity
Assignee: Celanese Corp
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Filing: 1975-06-05
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Granted: 1978-02-14
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Expires: 1995-06-05
Abstract
Abstract The internal structure of carbon fibers (as defined) is modified to yield a fibrous product having a bound oxygen content of about 3 to 30 percent by weight which exhibits substantially different bulk properties than that of the starting material. The carbon fiber precursor is contacted with a strong acid medium comprising nitric acid and optionally sulfuric acid and water (as defined) under conditions found capable of producing the desired internal chemical modification. In a preferred embodiment of the process the strong acid medium is formed by a combination (as defined) of fuming nitric acid and fuming sulfuric acid. The fibrous product exhibits, inter alia, reduced electrical and thermal conductivities, and particularly is suited for use as an ablative reinforcing medium.
Inventors
- 👤 Ilmar L. Kalnin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:20
CPC Classifications
D; D01; D01F; D01F9/00; D01F9/08; D01F9/12; D01F9/14; D01F9/20; D01F9/24; D01F11/00; D01F11/10; D01F11/12; D01F11/123; D01F9/145; D01F9/16; D01F9/21; D01F9/22; D01F9/28; D01F9/30
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
166 words
An improved process for the internal chemical modification of a carbonaceous fibrous material comprising at least 90 percent carbon by weight comprising: (a) contacting said fibrous material for about 5 to 120 minutes with a strong acid medium consisting essentially of nitric acid at a temperature of about 60° to 95° C. wherein the mole ratio of nitric acid to sulfuric acid present in said medium ranges between about 1 to 0 and 1 to 8 and the concentration of water in said acid medium ranges from 0 to 35 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acid adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 2
Dependent Claim
166 words
An improved process for the internal chemical modification of a carbonaceous fibrous material comprising at least 90 percent carbon by weight comprising: (a) contacting said fibrous material for about 5 to 120 minutes with a strong acid medium consisting essentially of nitric acid at a temperature of about 60° to 95° C. wherein the mole ratio of nitric acid to sulfuric acid present in said medium ranges between about 1 to 0 and 1 to 8 and the concentration of water in said acid medium ranges from 0 to 35 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acid adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 3
Dependent Claim
35 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said carbonaceous fibrous material which serves as the starting material is derived from an acrylic fibrous material.
Claim 4
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said carbonaceous fibrous material is a continuous length of a multifilament yarn.
Claim 5
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said carbonaceous fibrous material is a continuous length of a multifilament tow.
Claim 6
Dependent Claim
38 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said strong acid medium is at a temperature of about 70° to 85° C. when contacted with said fibrous material.
Claim 7
Dependent Claim
47 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said strong acid medium is a mixture of nitric acid and sulfuric acid and said mixture is formed upon the admixture of fuming nitric acid and fuming sulfuric acid.
Claim 8
Dependent Claim
38 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said removal of excess acid adhering to the resulting carbonaceous fibrous material is accomplished by evaporation at an elevated temperature.
Claim 9
Dependent Claim
34 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 1 wherein said removal of excess acid adhering to the resulting carbonaceous fibrous material is accomplished by washing.
Claim 10
Dependent Claim
167 words
An improved process for the internal chemical modification of a carbonaceous fibrous material containing at least 90 percent carbon by weight comprising: (a) contacting said fibrous material for about 5 to 120 minutes with a mixture consisting essentially of nitric acid and sulfuric acid at a temperature of about 60° to 95° C. wherein the mole ratio of nitric acid to sulfuric acid within said mixture ranges between about 8 to 1 and 1 to 8 and the concentration of water in admixture with said acids ranges from 0 to 30 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acids adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 11
Dependent Claim
167 words
An improved process for the internal chemical modification of a carbonaceous fibrous material containing at least 90 percent carbon by weight comprising: (a) contacting said fibrous material for about 5 to 120 minutes with a mixture consisting essentially of nitric acid and sulfuric acid at a temperature of about 60° to 95° C. wherein the mole ratio of nitric acid to sulfuric acid within said mixture ranges between about 8 to 1 and 1 to 8 and the concentration of water in admixture with said acids ranges from 0 to 30 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acids adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 12
Dependent Claim
35 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 9 wherein said carbonaceous fibrous material which serves as the starting material is derived from an acrylic fibrous material.
Claim 13
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said carbonaceous fibrous material is a continuous length of a multifilament yarn.
Claim 14
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said carbonaceous fibrous material is a continuous length of a multifilament tow.
Claim 15
Dependent Claim
38 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said mixture of acids is at a temperature of about 70° to 85° C. when contacted with said fibrous material.
Claim 16
Dependent Claim
39 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said mixture of nitric acid and sulfuric acid is formed upon the admixture of fuming nitric acid and fuming sulfuric acid.
Claim 17
Dependent Claim
38 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said removal of excess acids adhering to the resulting carbonaceous fibrous material is accomplished by evaporation at an elevated temperature.
Claim 18
Dependent Claim
34 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 10 wherein said removal of excess acids adhering to the resulting carbonaceous fibrous material is accomplished by washing.
Claim 19
Dependent Claim
175 words
An improved process for the internal chemical modification of a carbonaceous fibrous material containing at least 90 percent carbon by weight which is derived from an acrylic fibrous material comprising: (a) contacting said fibrous material for about 10 to 30 minutes with a mixture consisting essentially of nitric acid and sulfuric acid at a temperature of about 70° to 85° C. wherein the mole ratio of nitric acid to sulfuric acid within the admixture ranges between about 8 to 1 and 1 to 8 and the concentration of water in admixture with said acids ranges from 0 to 30 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acids adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 20
Dependent Claim
175 words
An improved process for the internal chemical modification of a carbonaceous fibrous material containing at least 90 percent carbon by weight which is derived from an acrylic fibrous material comprising: (a) contacting said fibrous material for about 10 to 30 minutes with a mixture consisting essentially of nitric acid and sulfuric acid at a temperature of about 70° to 85° C. wherein the mole ratio of nitric acid to sulfuric acid within the admixture ranges between about 8 to 1 and 1 to 8 and the concentration of water in admixture with said acids ranges from 0 to 30 mole percent based upon the total mole concentration of said acids and said water, and (b) removing excess acids adhering to the resulting carbonaceous fibrous material to yield a fibrous product containing about 3 to 30 percent bound oxygen by weight which exhibits a substantially reduced electrical conductivity by at least 40 percent when compared to that of the carbonaceous fibrous material prior to said contact and a single filament tenacity of at least 200,000 psi.
Claim 21
Dependent Claim
35 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said carbonaceous fibrous material which serves as the starting material is derived from an acrylic fibrous material.
Claim 22
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said carbonaceous fibrous material is a continuous length of a multifilament yarn.
Claim 23
Dependent Claim
30 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said carbonaceous fibrous material is a continous length of a multifilament tow.
Claim 24
Dependent Claim
39 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said mixture of nitric acid and sulfuric acid is formed upon the admixture of fuming nitric acid and fuming sulfuric acid.
Claim 25
Dependent Claim
38 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said removal of excess acids adhering to the resulting carbonaceous fibrous material is accomplished by evaporation at an elevated temperature.
Claim 26
Dependent Claim
34 words
An improved process for the chemical modification of a carbonaceous fibrous material in accordance with claim 17 wherein said removal of excess acids adhering to the resulting carbonaceous fibrous material is accomplished by washing.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-02-13 | 1981-08-15 | 1982-02-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-02-13 | 1985-08-15 | 1986-02-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-02-13 | 1989-08-15 | 1990-02-14 | $7700.00 | Window Closed / Lapsed |