Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
  • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
  • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
  • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
  • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
  • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
  • D01F9/225—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles from stabilised polyacrylonitriles

Definitions

• acrylonitrile polymer carbon precursor fibers are subjected to low temperatures i.e. 220-250 o c for relatively long periods of time in order to avoid too rapid an exotherm which leads to breakage of the tows.
• U.S. Patent 3,412,062 is representative of the prior art which teaches the stabilization of such fibers for 24-50 hours at 220°C while preventing the fibers from shrinking more than 12% by applying tension thereto. In some instances, the fiber is allowed to stretch up to 36%.
• the process of the present invention involves the stabilization of carbon fiber precursors in at least two stages.
• the first stage is conducted at a temperature at which the maximum plasticity of the polymer is attained while stretching the fiber from about 10-50%.
• the second stage is conducted, while the fiber is under tension, at a temperature ranging from about 200-300 o C, but higher than that of the first stage. Total residence time in both stages is 10-60 minutes.
• the process of the present invention is directed to the production of a carbon fiber precursor wherein an acrylonitrile polymer fiber is subjected to oxidation by heating said fiber in an oxidizing atmosphere for a time sufficient to permit substantially complete permeation of oxygen throughout the fiber structure.
• the processes encompasses the improvement which comprises conducting the stabilization (oxidation) in at least two stages, the first stage at a temperature substantially at which the maximum plasticity of the polymer is attained and while stretching the fiber from about 10-50%.
• the second stage is conducted while the fiber is maintained under a tension of from about 0.01-0.2 g/d and at a temperature ranging from about 200-300 o C but in any event, higher than the temperature employed in the first stage.
• the total residence time of the fiber in the oxidation procedure ranges from about 15-60 minutes.
• the tension of the fiber is maintained as in the second stage and at a temperature ranging from about 200-300°C, but at least equal to that of the second stage.
• the acrylonitrile fibers used herein are produced from polymers well known to those skilled in the art. Although polyacrylonitrile per se can be employed, the polymer is usually a copolymer or terpolymer of at least about 85 weight percent of acrylonitrile and the remainder a comonomer or comonomers copolymerizable with the acrylonitrile.
• Useful comonomers include methyl methacrylate, acrylic acid, methacrylic acid, methylacrylate, acrylamide, .6-hydroxypropyl acrylate and the like.
• the polymer fiber is heated substantially to its maximum plasticity.
• the temperature at which the polymer exhibits its maximum plasticity is, of course, different for each polymeric system undergoing stabilization. Such temperature can be ascertained by testing of the polymer beforehand to determine at what temperature maximum plasticity is achieved.
• said temperature usually ranges from about 200-275°C, generally from about 240-260°C, and it is to this temperature most polymers must be heated in the first stage of the novel process set forth herein.
• the polymer is stretched from about 10-50%, preferably from about 20-30% during the first stage heat treatment.
• the oxidation may be conducted in any oxygen containing media with air being preferred. Extraneous oxygen may be added, if desired.
• the fiber from the first oxidation stage is heated in the second stage to a temperature ranging from about 200-300°C, preferably from about 220-270°C, but higher than that temperature employed in the first stage.
• the total residence time of the polymer fiber in the stages of the oxidation treatment ranges from about 15-60 minutes, preferably 20-45 minutes.
• the residence time of the fiber in the second stage should be at least about twice that of the fiber in the first stage.
• the residence time of the third stage should be about equal to that of the second stage, the second stage again being at least about twice that of the first stage.
• the stabilized polymer fiber is recovered from the stabilization treatment, it can then be carbonized in the usual manner i.e. by heating to about 700-1200°C in an inert atmosphere.
• the carbonized fiber can then be further treated i.e. graphitized, by heating to a temperature of about 1200-3000°C, again under inert conditions, such as taught in U.S. Patent 4,411,110, incorporated herein by reference.
• Run B utilizing temperatures below those of Run A, i.e. those normally employed in carbon fiber precursor stabilization, requires 2 hours of total residence time to achieve a stabilized fiber having properties substantially equivalent to those of the fiber resulting from Run A.
• Run C shows, that when utilizing temperatures similar to those of Run B while stretching in accordance with Run A, the tow breaks and no useful fiber results.
• a precursor fiber tow containing 3,000, 1.3 denier filaments of the polymer of Example 1 is subjected to stabilization according to the conditions set forth in Table II, below (Runs E, F, H and I). Comparative runs utilizing conditions outside the scope of the process of the present invention, (Runs D and G) and other, commercially available, carbon fiber precursors (Runs H and I) are also shown.
• the stabilized fibers are subsequently carbonized by passing the fibers through a detarring furnace at a temperature of 600°C while the fiber is stretched 4%.
• the tow is then exposed to a graphtizing temperature of 1250°C for 30 seconds while relaxing 5%. Carbon fiber properties are also shown in Table II.
• Runs E and F of Table II A comparison of Runs E and F of Table II with Run D clearly shows that the process of the present invention (Runs E and F) produce carbon fibers having properties at least equivalent to, if not superior to, those using the lower stabilization temperatures of the prior art procedures (Run D).
• Run H l results in a carbon fiber at least as good as the prior art process, Run G l .
• Run 1 2 using the present process, provided a very poor carbon fiber, probably because the fiber was damaged during stabilization by the temperatures employed. Since the exact structural and chemical nature of the precursor fibers of Run 1 2 is not known, further discussion of why the polymer failed is pure -speculation.
• Example 1 Following the procedure of Example 1 (Run A) except that the polymer comprises 91.2% acrylonitrile, 4.8% meth- ylmethylacrylate, 2.0% methacrylic acid and 2.0% -hydroxypropylacrylate, similar results are achieved.
• the polymer is subjected to stabilization in accordance with the conditions set forth in Table III, below.
• the stabilized fiber is subsequently carbonized by passing the fiber through a detarring furnace at a temperature of 600°C for 30 seconds while the fiber is stretched 4%, and then graphitized by passing the carbonized fiber at 1350°C for 30 seconds while relaxing 5%.
• the resultant carbon fiber properties are also shown in Table III.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Inorganic Fibers (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=24348348

Family Applications (1)

Country Status (2)

Families Citing this family (2)

Citations (4)

• 1985
  • 1985-02-04 EP EP85101144A patent/EP0154175A3/fr not_active Ceased
  • 1985-03-04 JP JP4135885A patent/JPS60209019A/ja active Pending

Patent Citations (4)

Also Published As

Similar Documents

Legal Events