Controlled surface electrical resistance carbon fiber sheet product

Abstract

A method of manufacturing controlled surface electrical resistivity carbon fiber sheet products employing a carbonizable starting material, heating and drawing the starting material (if required), stabilizing and oxidizing the starting material if required at an elevated temperature of the order of 220 degrees Centigrade to effect molecular aromatic rearrangement of the starting material, partially carbonizing the oxidized starting material at an elevated temperature values in an oxygen free atmosphere within a furnace having an elevated temperature extending over a temperature range from about 370 degrees Centigrade to about 1400 degrees Centigrade by soaking the. The starting material is soaked at an elevated temperature for a predetermined period of time to provide a known preselected surface electrical resistivity to the partially carbonized material corresponding to that required to provide the preselected desired surface electrical resistance for the finished products. The partially carbonized material thus treated is formed into end carbon fiber sheet products having the form of paper, woven fabric and the like having a predetermined desired surface electrical resistivityresistance. The starting carbonizable material consists essentially of PAN.

Description

TECHNICAL FIELD

This invention relates to a novel method of manufacture of homogeneous partially carbonized volume homogeneous a weaving, knitting or other similar operations. The plied or twisted spun yarn then is supplied to a fabric weaving operation 36, a knitting or other fabric forming operation which provides a fabric of desired characteristics for an intended end application. From the fabric forming operation, the fabric is then supplied to a batch carbonization treatment furnace 37 where the fabric is carbonized at an elevated temperature in a vacuum within the furnace whose temperature increases from ambient up to a selected temperature of about 1400 degrees Centigrade and then is force cooled back to ambient over a period of about three to four days. The fabric is soaked at the elevated temperatures pursuant to the temperature-surface resistance treatment schedule depicted in FIG. 4 of the drawings in order to provide the fabric with a preselected electrical surface resistance. After carbonization in the above described manner, the output carbonized fabric sheet product is then accumulated as on a take-up roll shown at 38.

The resulting carbon fiber sheet products formed either by the manufacturing steps illustrated and described with relation to FIG. 1 or those shown in FIG. 2 are sold under the trademark "PANEX" and can be supplied with electrical resistivities of any value within the range of values depicted in FIG. 4. Because the temperature-resistivity treatment schedule provides a substantially linearly changing volume electrical resistivity for each incremental increase in temperature during the soak period, carbon fiber sheet products having precise and evenly distributed surface electrical resistivities resistances can be manufactured in accordance with the invention.

INDUSTRIAL APPLICABILITY

A method of fabricating controlled surface electrical resistivity carbon fiber sheet products is described which employs carbonizable fiber filament starting materials which thereafter are heat treated in a furnace at preselected elevated temperatures in an oxygen free atmosphere and thereafter further processed to result in finished homogeneous carbon fiber sheet products having a desired preselected surface electrical resistivity over a wide range of values and which is uniformly disbursed throughout the carbon fiber sheet productresistance.

Having described several embodiments of a novel method of fabricating controlled surface electrical resistivity resistance carbon fiber sheet products and the products resulting therefrom in accordance with the invention, it is believed obvious that other modifications and variations of the invention will be suggested to those skilled in the art in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

Claims

1. A method of manufacturing a plurality of different value controlled resistivity carbon fiber sheet products employing a carbonizable fiber starting material; said method comprising oxidizing and stabilizing the carbonizable fiber starting material at an elevated temperature of the order of 220 degrees Centigrade to effect molecular aromatic rearrangement of the fibers, selectively partially carbonizing the previously oxidized and stabilized fiber starting material for a predetermined time period in an oxygen free atmosphere within a furnace at a selected temperature values within a temperature range from 370 degrees Centigrade to about 1300 degrees Centigrade by soaking the stabilized fiber starting material at the selected temperature for the predetermined period of time to provide a desired preselected known volume electrical resistivity to the partially carbonized fibers corresponding to that volume electrical resistivity value required to provide the preselected desired surface resistance value for the finished sheet products, and thereafter processing the partially carbonized fibers into desired electrical resistivity homogeneous carbon fiber sheet products having the form of non-woven paper or woven or knitted fabric sheet products having the preselected desired surface electrical resistivities resistances.

2. The method according to claim 1 wherein the steps of heating and drawing the fiber starting carbonizable fiber material is added prior to is heated and drawn prior to oxidizing and stabilizing the fibers.

3. The method according to claim 1 wherein the fiber starting carbonizable material consists essentially of polyacrylonitrile (PAN).

4. The method according to claim 2 wherein the fiber carbonizable starting material comprises polyacrylonitrile (PAN).

5. The method according to claim 1 wherein the step of processing the partially carbonized fiber material into a desired end sheet product comprises chopping the partially carbonized fiber material into bundles of fine fibers having a length of from 1/8 to 1 inch, supplying the chopped carbonized fibers to a mixer for mixing with water in copious quantities to form a slurry comprised of about 83% partially carbonized fibers, 14% cellulose, 2% polyvinylalcohol and the remainder a resin to result in a highly dilute solution wherein the constituents of the slurry exclusive of the water amount to about 0.12% of the overall slurry solution including water, adjusting the ph factor of the overall slurry solution to a ph factor of about 8-9 with ammonia, supplying the slurry solution to a wet lay paper formation process to form wet sheets of carbon fiber paper, conveying the wet sheets of carbon fiber paper to a series of dryer cans and taking up the sheets of dry carbon fiber paper sheets continuously on a take-up roll for storage and use.

6. The method according to claim 2 wherein the step of processing the partially carbonized fiber material into a desired end sheet product comprises chopping the partially carbonized fiber material into bundles of fine fibers having a length of from 1/8 to 1 inch, supplying the chopped partially carbonized fibers to a mixer for mixing with water in copious quantities to form a slurry comprised of about 83% partially carbonized fibers, 14% cellulose, 2% polyvinylalcohol and the remainder a resin to result in a highly dilute solution wherein the constituents of the slurry exclusive of the water amount to about 0.12% of the overall slurry solution including water, adjusting the ph factor of the overall slurry solution to a ph factor of about 8-9 with ammonia, supplying the slurry solution to a wet lay paper formation process to form wet sheets of carbon fiber paper, conveying the wet sheets of carbon fiber paper to a series of dryer cans and taking up the sheets of dry carbon fiber paper continuously on a take-up roll for storage and use.

7. The method according to claim 5 wherein the starting fiber carbonizable material consists essentially of polyacrylonitrile (PAN).

8. The method according to claim 6 wherein the starting fiber carbonizable material consists essentially of polyacrylonitrile (PAN).

9. The method of manufacture according to claim 1 wherein the carbonizable fiber starting material initially used comprises 1.5 dpf yarn and wherein the step of processing the partially carbonized fiber material into desired end carbon fiber sheet products comprises forming a continuous filament yarn and thereafter weaving the partially carbonized continuous filament yarn into fabric.

10. The method according to claim 9 wherein the starting fiber carbonizable material consists essentially of polyacrylonitrile (PAN).

11. A method of manufacturing a plurality of different value controlled resistivity carbon fiber sheet products employing a carbonizable, previously oxidized and stabilized fiber starting material; said method comprising oxidizing and stabilizing the fiber starting material at an elevated temperature of the order of 220 degrees Centigrade to effect molecular aromatic rearrangement of the fibers, forming a an oxidized and stabilized tow, stretching and breaking the stabilized tow, forming the stabilized stretched and broken fiber filaments into sliver comprised of, large bundles of discontinuous filaments in an untwisted condition, converting the sliver into roving, spinning the roving into a spun yarn, plying or twisting the spun yarn, weaving or knitting the plied and twisted spun yarn into fabric, and selectively partially carbonizing the fabric thus formed at a preselected elevated temperature values for a predetermined time period in an oxygen free atmosphere within a furnace having a continuously increasing temperature profile within the range from about 370 degrees Centigrade to about 1300 degrees Centigrade by soaking the fabric at the preselected elevated temperature for the predetermined period of time to provide a known preselected surface electrical volume resistivity to the partially carbonized fiber filament in the fabric corresponding to that value of electrical volume resistivity required to provide the preselected desired surface resistance for the finished fabric.

12. The method according to claim 11 wherein the step of heating and drawing the starting carbonizable fiber material is added prior to oxidizing the starting material.

13. The method according to claim 11 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

14. The method according to claim 12 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

15. A method of manufacturing a plurality of different value controlled resistivity surface resistance carbon fiber sheet products employing a carbonized carbonizable previously oxidized and stabilized fiber starting material; said method comprising oxidizing and stabilizing the carbonizable fiber starting material at an elevated temperature of the order of 220 degrees Centigrade to effect molecular aromatic rearrangement of the fibers, selectively partially carbonizing the stabilized fibers at an elevated temperature values in an oxygen free atmosphere within a furnace having an increasing temperature profile extending over a temperature range from about 370 degrees Centigrade to about 1300 degrees Centigrade by soaking the stabilized fibers at a preselected elevated temperature for a predetermined period of time in accordance with a prescribed temperature-time-resistivity schedule to provide a preselected known electrical volume resistivity to the partially carbonized fibers corresponding to that required to provide the preselected desired surface resistance for the finished sheet products, processing the partially carbonized fibers into desired end sheet products having preselected desired surface electrical resistivities resistances, and wherein the steps of processing the carbonized fibers into a desired end carbon fiber sheet product include chopping the selectively carbonized fibers into bundles of fine fibers having a length of from 1/8 to 1 inch, supplying the chopped carbonized fibers to a mixer for mixing with water in copious quantities to form a slurry comprised of about 83% carbonized fibers, 14% cellulose, 2% polyvinylalcohol and the remainder a resin to result in a highly dilute solution wherein the constitutents constituents of the slurry exclusive of the water amount to about 0.12% of the overall slurry solution including water, adjusting the ph factor of the overall slurry solution of a ph factor of about 8-9 with ammonia, supplying the slurry solution to a wet lay paper formation process to form wet sheets of carbon fiber paper, conveying the wet sheets of carbon fiber paper to a series of dryer cans and taking up the sheets of dry carbon paper continuously on a take-up roll for storage and use.

16. The method of manufacture according to claim 15 wherein the method further comprises initially using as a carbonizable fiber starting material is a 1.5 dpf yarn and wherein the step of forming the carbonized fiber material into a desired carbon fiber sheet product further comprises forming a carbonized continuous filament yarn and thereafter weaving the carbonized continuous filament yarn into fabric.

17. The method according to claim 15 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

18. The method according to claim 16 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

19. The method according to claim 15 wherein the step of heating and drawing the starting carbonizable fiber material is added prior to oxidizing the carbonizable starting material.

20. The method according to claim 16 wherein the step of heating and drawing the starting carbonizable fiber material is added prior to oxidizing the carbonizable starting material.

21. The method according to claim 19 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

22. The method according to claim 20 wherein the starting carbonizable fiber material consists essentially of polyacrylonitrile (PAN).

23. The product of the process according to claim 1.

24. The product of the process according to claim 3.

25. The product of the process according to claim 5.

26. The product of the process according to claim 7.

27. The product of the process according to claim 9.

28. The product of the process according to claim 10.

29. The product of the process according to claim 11.

30. The product of the process according to claim 13.

31. The product of the process according to claim 15.

32. The product of the process according to claim 16.

33. A method of manufacturing homogeneous controlled surface resistance carbon fiber sheet products which exhibit a predetermined surface electrical resistance from a carbonizable fiber starting material, the method comprising partially carbonizing previously oxidized and stabilized fiber starting material by subjecting it to a heat-soak treatment within a preselected temperature range for a predetermined time period in an oxygen-free atmosphere within a furnace and, either before or after the partial carbonizing step, processing the fibers into a desired product form; characterized in that the surface electrical resistance of the resulting finished product is time/temperature controlled during the partial carbonizing step so as to provide a predesigned electrical volume resistivity to the resultant partially carbonized fibers corresponding in value to a known preselected electrical volume resistivity value required to provide the preselected desired surface resistance for the finished carbon fiber sheet products; and wherein the temperature is within the range of about 370 degrees Centigrade to about 1300 degrees Centigrade for a predetermined time period dependent principally upon the mass of the homogenous partially carbonized sheet product. PG,34 34. A method according to claim 33, wherein the furnace used for the partial carbonizing process has a continuously increasing temperature profile over the duration of the carbonizing. 35. A method according to claim 34, wherein the furnace is a continuous line carbonizer divided into different temperature zones. 36. A method according to claim 35, wherein the continuous line carbonizer is divided into four temperature zones having operating temperatures of about 370 degrees Centigrade for the first zone, 650 degrees Centigrade for the second zone, 790 degrees Centigrade for the third zone and a temperature not exceeding about 1300 degrees Centigrade for the fourth zone, the temperature of the fourth zone being selected to control the surface electrical resistivity of the resulting partially carbonized fibers and thus the surface electrical resistance of the finished product. 37. A method according to claim 33 wherein the carbonizable fiber starting material comprises polyacrylonitrile. 38. A method according to claim 33 wherein the carbonizable fiber starting material is heated and drawn and then oxidized and stabilized before the partial carbonizing step. 39. A homogeneous partially carbonized carbon fiber product having a predetermined surface electrical resistance and substantially free of non-carbonized fiber filaments made by a process

according to claim 33. 40. A homogeneous partially carbonized fiber sheet product free of non-carbonized fiber starting materials and having a homogeneous partially carbonized surface which exhibits a predesigned surface electrical resistance that is determined in advance by a predesigned partial carbonizing time/heat treatment of previously oxidized and stabilized non-carbonized fiber starting material and being the product of a partial carbonizing treatment designed to provide the resultant desired predetermined surface electrical resistance to the end product by being heated for a predetermined period of time at temperature values ranging between about 370 degrees Centigrade and about 1300 degrees Centigrade to provide a known preselected electrical volume resistivity to the partially carbonized fibers corresponding to that required to provide the preselected desired surface electrical resistance for the finished sheet products.