Method for producing carbon fiber

Patent metadata

Field	Value
Publication number	US-12006595-B2
Application number	US-202217895949-A
Country	US
Kind code	B2
Filing date	Aug 25, 2022
Priority date	Aug 25, 2021
Publication date	Jun 11, 2024
Grant date	Jun 11, 2024

Abstract

The present invention relates to a method for producing a carbon fiber. In the method for producing the carbon fiber, a high pure acrylonitrile monomer with specific contents of impurities and a comonomer are used to produce an acrylonitrile copolymer, and the acrylonitrile copolymer is subjected to a spinning operation, a stretching operation, an oxidation treatment and a carbonization treatment in sequence, for obtaining the carbon fiber. The acrylonitrile copolymer with an appropriate falling-ball viscosity and an appropriate weight-average molecular weight is beneficial to the spinning operation, thereby reducing an inner pore diameter and enhancing strength of the resulted carbon fiber.

First claim

What is claimed is:

1. A method for producing a carbon fiber, comprising:
mixing a copolymer solution of acrylonitrile copolymer consisting of an acrylonitrile monomer, a comonomer, an initiator and a solvent, and performing a polymerization, so as to obtain an acrylonitrile copolymer, wherein the acrylonitrile monomer includes impurities comprising water, methylpropenenitrile, propionylnitrile, oxazole, 4-methoxyphenol, butenone, iron, copper and (meth)acrylic acid alkyl ester, based on a weight of the acrylonitrile monomer as 100 weight percent (wt. %), a content of the acrylonitrile is more than 99.93 wt. %, and based on the content of the acrylonitrile monomer as 1×10 6 ppm, a content of the water is more than or equal to 48 ppm and less than 70 ppm, a content of the methylpropenenitrile is less than 2 ppm, a content of the propionylnitrile is less than 1 ppm, a content of the oxazole is less than 2 ppm, a content of the 4-methoxyphenol is less than 40 ppm, a content of the butenone is less than 2 ppm, a content of the iron is less than 0.001 ppm, a content of the copper is less than 0.002 ppm, and a content of the (meth)acrylic acid alkyl ester is less than 1 ppm, wherein based on a total weight of the acrylonitrile monomer and the comonomer as 100 wt. %, a content of the initiator is not more than 0.1 wt. %,
performing a spinning operation on the acrylonitrile copolymer, so as to obtain a raw filament of the acrylonitrile copolymer, wherein a falling-ball viscosity of the acrylonitrile copolymer is 620 seconds to 700 seconds, and a molecular weight distribution of the acrylonitrile copolymer is less than 2.2;
performing a stretching operation on the raw filament of the acrylonitrile copolymer, so as to obtain a carbon fiber precursor;
performing an oxidation treatment on the carbon fiber precursor, so as to obtain an oxidized fiber; and
performing a carbonization treatment on the oxidized fiber, so as to obtain the carbon fiber.

2. The method for producing the carbon fiber of claim 1 , wherein based on the total weight of the acrylonitrile monomer and the comonomer as 100 wt. %, a content of the acrylonitrile monomer is 98.0 wt. % to 99.8 wt. %, and a content of the comonomer is 0.2 wt. % to 2.0 wt. %.

3. The method for producing the carbon fiber of claim 1 , wherein the comonomer comprises itaconic acid.

4. The method for producing the carbon fiber of claim 1 , wherein a content of the solvent is three to eight times of the total weight of the acrylonitrile monomer and the comonomer.

5. The method for producing the carbon fiber of claim 1 , wherein the polymerization is performed at 60° C. to 70° C. for 4 hours to 6 hours, heated to 70° C. to 80° C. for 1 hour to 3 hours, and maintained for 7 hours to 9 hours.

6. The method for producing the carbon fiber of claim 1 , wherein a weight-average molecular weight of the acrylonitrile copolymer is 380,000 g/mole to 450,000 g/mole.

7. The method for producing the carbon fiber of claim 1 , wherein a total stretching ratio of the raw filament of the acrylonitrile copolymer is 11.2 to 12.8 after the stretching operation.

8. The method for producing the carbon fiber of claim 1 , after the stretching operation, further comprising:
coating a finishing oil on the carbon fiber precursor, so as to obtain an oil coated carbon fiber precursor.

9. The method for producing the carbon fiber of claim 8 , further comprising:
performing a drying operation on the oil coated carbon fiber precursor, so as to obtain a dried carbon fiber precursor.

10. The method for producing the carbon fiber of claim 1 , wherein the oxidation treatment is performed at 200° C. to 300° C.

11. The method for producing the carbon fiber of claim 1 , wherein a stretching ratio of the carbon fiber precursor after the oxidation treatment is 0.7 to 0.9 in comparison with an original length of the carbon fiber precursor before the oxidation treatment.

12. The method for producing the carbon fiber of claim 1 , after the carbonization treatment, further comprising:
performing a surface oxidation treatment on the carbon fiber, so as to obtain a surface treated carbon fiber.

13. The method for producing the carbon fiber of claim 1 , wherein an inner pore diameter of the carbon fiber is less than 10 nm.

14. A method for producing a carbon fiber, comprising:
mixing a copolymer solution of acrylonitrile copolymer consisting of an acrylonitrile monomer, a comonomer, an initiator and a solvent, and performing a polymerization, so as to obtain an acrylonitrile copolymer, wherein the acrylonitrile monomer includes impurities comprising water, methylpropenenitrile, propionylnitrile, oxazole, 4-methoxyphenol, butenone, iron, copper and (meth)acrylic acid alkyl ester, based on a weight of the acrylonitrile monomer as 100 weight percent (wt. %), a content of the acrylonitrile is more than 99.93 wt. %, and based on the content of the acrylonitrile monomer as 1×10 6 ppm, a content of the water is more than or equal to 48 ppm and less than 70 ppm, a content of the methylpropenenitrile is less than 2 ppm, a content of the propionylnitrile is less than 1 ppm, a content of the oxazole is less than 2 ppm, a content of the 4-methoxyphenol is less than 40 ppm, a content of the butenone is less than 2 ppm, a content of the iron is less than 0.001 ppm, a content of the copper is less than 0.002 ppm, and a content of the (meth)acrylic acid alkyl ester is less than 1 ppm; and based on a total weight of the acrylonitrile monomer and the comonomer as 100 wt. %, a content of the comonomer is 0.2 wt. % to 2.0 wt. %, and a content of the initiator is not more than 0.1 wt. %;
performing a spinning operation on the acrylonitrile copolymer, so as to obtain a raw filament of the acrylonitrile copolymer, wherein a falling-ball viscosity of the acrylonitrile copolymer is 620 seconds to 650 seconds, and a molecular weight distribution of the acrylonitrile copolymer is less than 2.2;
performing a stretching operation on the raw filament of the acrylonitrile copolymer, so as to obtain a carbon fiber precursor;
performing an oxidation treatment on the carbon fiber precursor, so as to obtain an oxidized fiber; and
performing a carbonization treatment on the oxidized fiber, so as to obtain the carbon fiber.

15. The method for producing the carbon fiber of claim 14 , wherein an inner pore diameter of the carbon fiber is less than 10 nm, and tensile strength of the carbon fiber is more than 650 KSI.

Assignees

• Formosa Plastics Corp

Inventors

• Hwang Long-Tyan
• Hung Chia-Chi
• Tsai Kun-Yeh
• Chen Ching-Wen
• Chou Wen-Ju

Classifications

• C08K2003/0856

  Iron · CPC title

• C08K2003/085

  Copper · CPC title

• D01F9/225

  from stabilised polyacrylonitriles · CPC title

• D06M2101/28

  Acrylonitrile; Methacrylonitrile · CPC title

• D01F6/36

  comprising unsaturated carboxylic acids or unsaturated organic esters as the major constituent · CPC title