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
  • D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
  • D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
  • D01F11/14—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with organic compounds, e.g. macromolecular compounds

Definitions

• This invention provides a method for increasing the tenacity of pitch-based carbon fiber yarn comprising impregnating a pitch-based carbonized or partially carbonized fiber yarn with a carbonizable resin precursor, polymerizing the precursor in situ to form the resin and subjecting the impregnated yarn to a temperature in excess of 1000°C in an inert atmosphere to carbonize the resin.
• the carbon fiber yarn to be strengthened in accordance with the present invention is a pitch-based yarn.
• This yarn may be prepared by the general procedures described in U.S. Patent No. 4,005,183. Either carbonized or partially carbonized yarn may be employed.
• a solution of a carbonizable resin precursor is applied to the yarn.
• the object is to impregnate the fibers of the yarn with a material which will polymerize or polymerize further to a resinous product which will remain in place and leave a carbon residue within the fiber upon carbonization.
• the term "resin precursor" is intended to include unpolymerized or partially polymerized materials. Polymerization or resinification is often facilitated by application of heat. The resin must be capable of being carbonized, the usual temperature of carbonization being above 1000°C.
• suitable carbonizable resin precursors are partially polymerized phenolic condensation products, epoxy resins, furfural, furfuryl alcohol, partially polymerized furfuryl alcohol resin, urea condensation products, acrylic resins, vinyl resins, propylene glycol, etc.
• a sufficient amount of carbonizable resin precursor must be absorbed by the yarn to provide strengthening. Amounts yielding between about 0.1 and 10% of resin based on the weight of the yarn prior to impregnation have been found satisfactory.
• the weight gain is kept below 5%, particularly with partially carbonized fiber because such fibers are less able to absorb the resin precursors.
• the resin precursor have a high coking factor, that is, a high percentage of carbon yield when subjected to carbonization. Volatile impregnants which are entirely driven off in the heating step are clearly unsuitable.
• the yarn is passed through a bath containing the carbonizable resin precursor.
• the resin precursor is furfuryl alcohol, a partially polymerized furfuryl alcohol or combination thereof, it is desirable to incorporate a latent catalyst along with the precursor.
• a latent catalyst are commercially available and recommended for the purpose of catalyzing the polymerization of the resin precursor at elevated temperatures.
• One such catalyst is a complex of boron trifluoride and monoethylamine.
• Another catalyst is maleic anhydride.
• Use of a latent catalyst permits application of a low viscosity solution to the fiber with subsequent polymerization at the elevated temperatures. If the precursor were to polymerize significantly prior to application, the treating bath would be so viscous as to allow only a coating to be formed.
• Suitable solvents are those which will readily evaporate without leaving any harmful residues. Acetone has been found useful for this purpose.
• the viscosity of the impregnation bath should be sufficiently low as to permit permeation of the resin precursor into the fibers of the yarn, i.e., to fill the voids, cracks and other defects of the fiber. If the bath is too viscous, the yarn itself, rather than the fibers thereof, will entrap such amounts of resin precursor as to cause the fibers to stick to each other. Such fibers often break when attempts are made to separate them from each other. It will be understood that the resin content of the impregnating solution increases with age because partial polymerization is taking place. As this occurs, the viscosity of the bath increases and will influence the degree of fiber permeation.
• T/E/M Tenacity, elongation and modulus
• the yarn contained 496 filaments each having a diameter of about 10 microns.
• the carbonized yarn (at 1600°C) had an initial modulus of about 900 to 1000 grams per denier (gpd).
• Carbon fiber yarn was impregnated with furfuryl alcohol containing 1% latent catalyst (commercially available complex of boron trifluoride and monoethylamine (BF3.MEA).
• the fibers were heated at 4°C/min. to 150°C and held at 150°C for 32 minutes to polymerize the furfuryl alcohol. After polymerization the fibers were found to have gained 1.45% of their original weight. The fibers were then carbonized at 1584°C.
• An 11% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 14.6gpd/1.22%/1055gpd, T/E/M control fiber: 13.2gpd/1.17%/988 gpd).
• Carbon fiber yarn was impregnated with the solution used in Example 1. The solution had been aged for 22 days. The furfuryl alcohol was polymerized under the same conditions as in Example 1. After polymerization, the fibers were found to have gained 8.7% of their original weight. The fibers were then recarbonized at 1584°C. A 22% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 16.1gpd/1.25%/997gpd, T/E/M control fiber: 13.2gpd/1.17%/988gpd).
• Carbon fiber yarn was impregnated using a 90/10% by wt. mixture of furfuryl alcohol and furfural modified furfuryl alcohol resin with 2% of the latent catalyst of Example 1.
• the fibers were heated at 4°C/min. to 120°C and held at 120°C for 32 minutes to polymerize the furfuryl alcohol/resin. After polymerization, the fibers were found to have gained 3.2% of their original weight.
• the fibers were then recarbonized at 1600°C. A 29% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 14.2gpd/1.23%/1025gpd, T/E/M control fiber: 11.0gpd/.95%/1081gpd).
• Carbon fiber yarn was impregnated using a 90/10% by wt. mixture of furfuryl alcohol and furfural modified furfuryl alcohol resin with 2% of the latent catalyst of Example 1.
• the fibers were heated at 4°C/min to 120° and held at 120°C for 32 minutes to polymerize the furfural modified resin. After polymerization, the fibers were found to have gained 6.1% of their original weight.
• the fibers were then recarbonized at 1600°C. A 24% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 15.1gpd/1.18%/1148gpd, T/E/M control fiber: 12.2gpd/1.023%/1095gpd).
• Carbon fiber yarn was impregnated using a 10% by wt. solution of furfural modified furfuryl alcohol resin dissolved in acetone. The fibers were then heated at 4°C/min to 120°C and held at 120°C for 32 minutes. The resulting weight gain was 7.7% of their original weight. The fibers were recarbonized at 1600°C. A 12% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 15.0gpd/1.41%/945, T/E/M control fiber: 13.4gpd/1.34%/868gpd).
• Carbon fiber yarn was impregnated using acetone containing 5% of the latent catalyst of Example 1.
• the fibers were then heated to 4°C/min to 120°C. and held at 120°C for 32 minutes. The resulting weight gain was less than 1%.
• the fibers were then recarbonized at 1600°C. No increase in strength resulted (T/E/M impregnated fiber: 13.7gpd/1.13%/1131gpd, T/E/M control fiber: 14.2gpd/1.07%/1272gpd).
• This example shows treatment with a non-resin forming medium did not result in strength improvement.
• Carbon fiber yarn was impregnated using propylene glycol containing 5% of the latent catalyst of Example 1. The fibers were then heated at 4°C/min to 200°C and held at 200°C for 32 minutes. A resin was formed from propylene glycol under these conditions. The resulting weight gain was less than 1%. The fibers were then recarbonized at 1600°C. A 10% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 13.2gpd/ 1.05%/1133gpd, T/E/M control fiber: 12.0gpd/.947%/1141gpd).
• Partially carbonized yarn (heated to 1000°C) was impregnated with furfuryl alcohol containing 2% of the latent catalyst of Example 1 which had been aged 72 hours.
• the fibers were heated at 4°C/min to 120°C and held at 120°C for 32 minutes to polymerize the furfuryl alcohol. The resulting weight gain was less than 1%.
• the fibers were then carbonized at 1599°C. A 24.5% improvement in tensile strength over the control fiber resulted.
• T/E/M impregnated fiber 14.5gpd/1.18%/1083gpd
• T/E/M control fiber 11.6gpd/97%/1080gpd).
• Carbon fiber was impregnated with furfural containing 2% of the catalyst of Example 1.
• the fibers were heated at 4°C/min to 120°C and held at 120°C for 32 minutes to polymerize the furfural. After polymerization, the fibers were found to have gained 0.1% of their orginal weight (weight gain from dipping was 3%).
• the fibers were then recarbonized at 1600°C. A 14% improvement in tensile strength over the control fiber resulted (T/E/M impregnated fiber: 13.8gpd/1.06%/1194gpd, T/E/M control fiber: 12.2gpd/1.023%/1095gpd).
• Carbon fiber was impregnated using a 95/5% by wt. mixture of furfuryl alcohol and furfural modified furfuryl alcohol resin with 5% maleic anhydride added as a latent catalyst.
• the fibers were heated at 4°C/min to 120°C and held at 120°C for 32 minutes to polymerize the furfuryl alcohol/resin. After polymerization, the fibers were found to have gained 6.1% of their original weight (weight gain after dipping was 160%). The fibers were then recarbonized at 1594°C.
• T/E/M impregnated fiber 14.6gpd/1.17%/1155gpd
• T/E/M control fiber 12.2gpd/1.02%/1087gpd

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Ceramic Products (AREA)
• Reinforced Plastic Materials (AREA)
• Inorganic Fibers (AREA)
• Chemical Treatment Of Fibers During Manufacturing Processes (AREA)

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Citations (2)

• 1987
  • 1987-06-19 EP EP87305466A patent/EP0251596A1/fr not_active Withdrawn
  • 1987-06-22 AU AU74585/87A patent/AU7458587A/en not_active Abandoned
  • 1987-06-23 CA CA000540393A patent/CA1255544A/fr not_active Expired
  • 1987-06-23 JP JP15458387A patent/JPS636115A/ja active Pending

Patent Citations (2)

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