Pitch-based carbon of graphite fiber and process for preparation thereof

Claim 2

A pitch-based carbon or graphite fiber having at least one lamellar micro-structure, characterized in that the lamellae of the micro-structure in at least 30% of the fiber cross-sectional area are arranged in the form of at least one leaf and the fiber has a tensile strength of at least 3.92 GPa (400 kg/mm 2 ).

Claim 3

A pitch-based carbon or graphite fiber as set forth in claim 1, having a substantially circular cross-sectional shape.

Claim 4

A pitch-based carbon or graphite fiber as set forth in claim 1, having an ellipsoidal cross-sectional shape.

Claim 5

A pitch-based carbon or graphite fiber as set forth in claim 1, having a multiangular cross-sectional shape.

Claim 6

A pitch-based carbon or graphite fiber as set forth in claim 1, having a multilobar cross-sectional shape.

Claim 7

A pitch-based carbon or graphite fiber as set forth in claim 1, having two to eight leaf-like lamellar structures in the cross-section.

Claim 8

A pitch-based carbon fiber as set forth in claim 1, having a modulus of at least 147 GPa (15 T/mm 2 ).

Claim 9

A pitch-based graphite fiber as set forth in claim 1, having a modulus of at least 294 GPa (30 T/mm 2 ).

Claim 10

A pitch-based carbon fiber as set forth in claim 1, having an orientation angle of 20 to 35° and a crystalline size of 1.8 to 3.5 nm (18 to 35 A), as measured for a fiber carbonized at 1300°C, and having a tensile strength of at least 5.39 GPa (550 kg/mm 2 ) and a modulus of 196 GPa (20 T/mm 2 ).

Claim 11

A process for preparing a pitch-based carbon or graphite fiber having at least one lamellar microstructure wherein the lamellae of the micro-structure in at least 30% of the fiber cross-sectional area are arranged in the form of at least one leaf, said process comprising: melt-spinning an optically anisotropic pitch having an optically anisotropic phase content of at least 50% through a spinneret in which at least one central line distance in a spinning hole simultaneously satisfies the following requirements I and II, wherein Ln stands for central line distances in mm in the spinning hole and Wn stands for wetted perimeter widths in mm in the spinning hole, and infusibilizing and carbonizing the formed pitch fiber.

Claim 12

A process for preparing a pitch-based carbon or graphite fiber having at least one lamellar microstructure wherein the lamellae of the micro-structure in at least 30% of the fiber cross-sectional area are arranged in the form of at least one leaf, said process comprising: melt-spinning an optically anisotropic pitch having an optically anisotropic phase content of at least 50% through a spinneret in which at least one central line distance in a spinning hole simultaneously satisfies the following requirements I and II, wherein Ln stands for central line distances in mm in the spinning hole and Wn stands for wetted perimeter widths in mm in the spinning hole, and infusibilizing and carbonizing the formed pitch fiber.

Claim 13

A process as set forth in claim 10, wherein the spinning hole consists of a single slit.

Claim 14

A process as set forth in claim 10, wherein the spinning hole consists of a plurality of slits.

Claim 15

A process as set forth in claim 12, wherein the spinning hole consists of 3 to 6 slits radially extending equiangularly with one point being the center.

Claim 16

A process as set forth in claim 10, wherein the central line of the spinning hole is a straight line.

Claim 17

A process as set forth in claim 10, wherein the central line of the spinning hole is a curved line.

Claim 18

A process as set forth in claim 10, wherein the central line of the spinning hole consists of a combination of a straight line and a curved line.

Claim 19

A process as set forth in claim 10, wherein the optically anisotropic pitch has an optical anisotropy of at least 80%.

Claim 20

A process as set forth in claim 10, wherein the optically anisotropic pitch has a melting point of 250°C to 350°C.

Claim 21

A process as set forth in claim 10, wherein the quinoline-soluble component content of the optically anisotropic pitch is at least 30% by weight.

Claim 22

A process as set forth in claim 10, wherein the spinning temperature at the melt-spinning step is higher by 40°C to 100°C than the melting point of the pitch.

Claim 23

A process as set forth in claim 10, wherein the optically anisotropic pitch is a substantially homogeneous optically anisotropic pitch having a melting point of 260°C to 320°C, which consists completely of optically anisotropic phase or consists essentially of continuous optically anisotropic phase wherein the optically anisotropic phase contains a spherical optically isotropic phase, the spherical bodies are contained in an amount not more than 15% and in a number not less than 100/mm 2 and have an average diameter not larger than 15 pm, each having a diameter not larger than 100 pm.

Claim 24

A process as set forth in claim 21, wherein the average diameter of the spherical optically isotropic phase bodies is not larger than 10 um.

Claim 25

A process as set forth in claim 21, wherein the spherical optically isotropic phase content is not more than 10%.

Claim 26

A process as set forth in claim 21, wherein the melting point of the optically anisotropic pitch is 270°C to 300°C.

Claim 27

A process as set forth in claim 21, wherein the substantially homogeneous optically anisotropic pitch is prepared through the first step of treating a starting pitch with an organic solvent to collect a solvent-insoluble fraction, the second step of subjecting the solvent-insoluble fraction to the hydrogenation treatment, the third step of filtering the hydrogenation product, and the fourth step of removing the solvent from the filtrate and heat-treating the residue at a temperature higher than 400°C under reduced pressure or atmospheric pressure.

Claim 28

A process as set forth in claim 25, wherein in the first step, the starting pitch is treated with an organic solvent system having a solubility coefficient of 8 to 10 at 25°C.

Claim 29

A process as set forth in claim 25, wherein in the second step, 100 to 300 parts by weight of a mixture of hydrogenated fused polycyclic aromatic compounds having at least 2 rings is added to 100 parts of a solvent-insoluble fraction obtained from a starting pitch and the obtained mixture is subjected to a hydrogenation treatment at a temperature of 400°C to 500°C under an autogeneous pressure.

Claim 30

A process as set forth in claim 25, wherein in the second step, 100 to 300 parts by weight of a hydrogenated nitrogen-containing aromatic compound or a mixture thereof is added to 100 parts by weight of a solvent-insoluble fraction obtained from a starting pitch and the obtained mixture is subjected to a hydrogenation treatment at 400°C to 500°C under an autogeneous pressure.

Claim 31

A process as set forth in claim 25, wherein in the second step, 100 to 300 parts by weight of a mixture of fused polycyclic aromatic compounds having at least 2 rings is added to 100 parts by weight of a solvent-insoluble fraction obtained from a starting pitch and the obtained mixture is hydrogenated in the presence or absence of a hydrogenation catalyst under a hydrogen pressure of at least 196 GPa (50 kg/cm 2 ) at a temperature of 350°C to 500°C.

Claim 32

A process as set forth in claim 25, wherein in the second step, 100 to 300 parts by weight of a nitrogen-containing aromatic compound to 100 parts by weight of a solvent-insoluble fraction obtained from a starting pitch and hydrogenating the obtained mixture in the presence or absence of a hydrogenation catalyst under a hydrogen pressure of at least 196 GPa (50 kg/cm 2 ) at a temperature of 350°C to 500°C.

Claim 33

A process as set forth in claim 10, wherein the optically anisotropic pitch to be spun is prepared by treating an optically isotropic pitch having a quinoline-insoluble component content of not more than 5% by weight with an organic solvent system having a solubility coefficient of about 8.0 to 10 at 25°C and heat treating the organic solvent-insoluble component at a temperature of 230°C to 450°C to convert it to a pitch having an optically anisotropic phase content of not less than 75%.

Claim 34

A process as set forth in claim 31, wherein the organic solvent system is benzene, toluene or a solvent mixture containing not less than 60% by volume of benzene and/or toluene.

Claim 35

A process as set forth in claim 31, wherein the organic solvent system is used in an amount of 5 to 150 ml per g of the pitch and the solvent treatment is carried out at 20°C to 200°C.

Claim 36

A process as set forth in claim 10, wherein the substantially homogeneous optically anisotropic pitch to be spun is prepared by denaturating an optically anisotropic pitch with an organic solvent system having a solubility coefficient of about 8.0 to 10 and treating the organic solvent-insoluble component with a mixture of unhydrogenated fused polycyclic aromatic compounds having at least 2 rings or an unhydrogenated nitrogen-containing aromatic compound or a mixture of such compounds in a nitrogen atmosphere at a temperature of 350 to 500°C, filtering the denaturation product, removing the solvent from the filtrate, and heat-treating the residue at a temperature higher than 400°C under reduced pressure or atmospheric pressure.