RU2741012C1 - Method of producing carbon fiber and based materials - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing carbon fiber and materials based thereon from initial cellulose fibrous material. Method involves impregnation of initial cellulose fibrous material in a liquid-phase organosilicon composition and subsequent thermal treatment, including thermal relaxation, pyrolysis, carbonization and graphitization, characterized in that said method is carried out in continuous mode, and as initial cellulose fibrous material, hydrate-and-cellulose threads are used, impregnation of which is carried out in zero-deformation mode in aqueous emulsion of liquid oligomeric resins with content of silanol groups reaching values from 5 % to 15 %, thermal treatment is carried out of textile materials made from hydrated cellulose threads impregnated in an aqueous emulsion of liquid oligomeric resins, wherein pyrolysis is carried out in eight temperature zones, in separate furnaces for each temperature zone in nitrogen medium with temperature rise by zones and degree of thread deformation: in the first zone, pyrolysis is carried out at temperature of 200–220 °C and degree of deformation of 0-(-5) %, in the second zone – at temperature of 220–240 °C and degree of deformation of 0-(-5) %, in the third zone – at temperature of 250–270 °C and degree of deformation of 0-(-5) %, in the fourth zone – at temperature of 270–300 °C and degree of deformation of 0-(+20) %, in the fifth zone – at temperature of 310–380 °C and degree of deformation of (-40)-(+45) %, in the sixth zone – at temperature of 410–540 °C and degree of deformation of (-5)-(+10) %, in the seventh zone – at temperature of 550–670 °C and degree of deformation of 0-(+10) %, in the eighth zone – at temperature of 680–720 °C and degree of deformation of 0-(+10) %, wherein pyrolysis products are removed from each temperature zone and afterburned in air flow, and thermal relaxation is carried out in air at temperature (180–200) °C in free shrinkage mode, carbonisation is carried out at temperature (1000–1100) °C, and graphitization is carried out at temperature (2200–2500) °C at drawing up to (+10 %).

EFFECT: improved physical and mechanical properties of carbon fibrous materials.

3 cl, 1 tbl, 8 ex

Description

The invention relates to the field of producing carbon fiber materials from hydrocellulose fibers used as reinforcing fillers of composite materials for heat-shielding and composite purposes.

There is a method of continuous production of carbon fiber from cellulose hydrate in the form of a unidirectional bundle, characterized by impregnation of cellulose hydrate fiber with fire retardants, which are an aqueous solution of ammonium chloride or an aqueous solution of ammonium sulfate, as well as additional impregnation with an organosilicon solution or suspension, which is a solution or suspension of polymethylsiloxane in acetone, drying the impregnated tow of hydrated cellulose fiber; then, before carbonization, pretreatment (thermal relaxation) of the dried tow of cellulose hydrate fiber is carried out in an oxygen-containing atmosphere, then a multi-zone non-oxidative stabilization carbonization is performed in a flow of an inert medium in a continuous furnace, during which pyrolysis products are selected in the zone of their greatest release and they are continuously oxidized in the nodes combustion, then the carbonized fiber is graphitized in nitrogen or argon (patent RU 2429316, IPC D01F 9/00, D01F 9/16, D01F 9/16, 20.09.2011).

This method has the disadvantage that it provides for the impregnation of the fibrous material before the stage of relaxation with a solution of polymethylsiloxane in acetone, which is a highly volatile toxic substance.

A known method of obtaining a carbon fiber structure from a cellulosic precursor, including the stages: spinning cellulose fibers from a solution of viscose or a solution of cellulose; washing cellulose fibers in water; impregnation of washed and undried cellulose fibers with an aqueous emulsion comprising from 5 to 50 wt. % of at least one silicone excipient suitable for increasing the carbonation of cellulose; drying the impregnated cellulose fibers, while after drying the content of the organosilicon auxiliary is in the range from 1.5 to 15 wt. % relative to the total mass of fibers; obtaining a fibrous structure consisting of impregnated and dried cellulose fibers; and carbonizing the fibrous structure, the carbonation comprising a slow pyrolysis step; before the stage of slow pyrolysis, relaxation is carried out in the air; after the final stage of carbonization, the fibrous structure is subjected to further heat treatment - graphitization (US Pat. RU 2394949, IPC D01F 9/16, D01F 9/14, 20.07.2010).

The known method has the disadvantage that it allows you to obtain carbon fiber materials with insufficiently high physical and mechanical characteristics.

The technical result when using the claimed invention is to improve the physical and mechanical properties of carbon fiber materials.

This technical result is achieved due to the fact that in the method of producing carbon fiber and materials based on it from the original cellulosic fibrous material, containing the impregnation of the original cellulosic fibrous material in a liquid-phase organosilicon composition and subsequent heat treatment, including thermal relaxation, pyrolysis, carbonization and graphitation, according to the invention , the above method is carried out in a continuous mode, and as the initial cellulosic fibrous material, hydrated cellulose threads are used, the impregnation of which is carried out in the mode of zero deformation in an aqueous emulsion of liquid oligomeric resins with a content of silanol groups, reaching values from 5% to 15%, during which they are subjected to heat treatment textile materials made of cellulose hydrate yarns impregnated in an aqueous emulsion of liquid oligomeric resins, and pyrolysis is carried out in eight temperature zones, in separate ovens for each temperature zone in a nitrogen atmosphere when the temperature rises temperatures by zones and the degree of deformation of the thread: in the first zone, pyrolysis is carried out at a temperature of 200-220 ° C and a degree of deformation of 0 - (- 5)%, in the second zone at a temperature of 220-240 ° C and a degree of deformation of 0 - (- 5 )%, in the third zone - at a temperature of 250-270 ° С and the degree of deformation 0 - (- 5)%, in the fourth zone - at a temperature of 270-300 ° С and the degree of deformation 0 - (+ 20)%, in the fifth zone - at a temperature of 310-380 ° С and the degree of deformation (-40) - (+ 45)%, in the sixth zone - at a temperature of 410-540 ° С and the degree of deformation (-5) - (+ 10)%, in the seventh zone - at a temperature of 550-670 ° C and a degree of deformation of 0 - (+ 10)%, in the eighth zone - at a temperature of 680-720 ° C and a degree of deformation of 0 - (+ 10)%, while the pyrolysis products are removed from each temperature zone and burned out in a stream of air, and thermal relaxation is carried out in air at a temperature of (180-200) ° C in the free shrinkage mode, carbonization is carried out at a temperature of (1000-1100) ° C, and graphitization is carried out at a temperature of (2200-2500) ° C at hood up to (+ 10%).

The specified technical result is also achieved by using hydrated cellulose yarns obtained by the viscose method or by the method of direct dissolution of cellulose; textile materials are ribbons, fabrics, threads, knitwear, felt, unidirectional material.

Achievement of the technical result became possible after carrying out research and development work and pilot tests of various organosilicon compounds. It has been established that it is possible to obtain the necessary technical indicators of carbon fibers by using oligomeric resins with a content of silanol groups reaching values from 5% to 15%. The presence of polar groups in the resins and low viscosity make it possible to uniformly wet the hydrated cellulose threads with good adhesion to their surface. Due to the high content of silanol groups during further heat treatment, they interact with the hydroxyl groups of the hydrated cellulose fiber with the formation of branched structures during polycondensation processes. The formed organosilicon branched cross-linked structures protect the cellulose hydrate threads from undesirable reactions with pyrolysis products, creating a protective shell.

Liquid oligomeric resins with a high content of silanol groups (5-15)%, emulsified in aqueous emulsions, were used as impregnating compounds to achieve the technical result.

After the application of silicon-containing impregnating compounds on the hydrated cellulose threads, thermal relaxation is carried out in air at a temperature of (180-200) ° C in the free shrinkage mode. At this technological stage, the relaxation of internal stresses formed in the previous stages of obtaining a thread from a hydrated cellulose fiber occurs, and also polycondensation processes in the deposited organosilicon compounds are completed as a result of thermo-oxidative reactions.

The hydrated cellulose filaments impregnated in an aqueous emulsion and thermorelaxed in air enter the stage of pyrolysis of the technological process for producing carbon fiber from hydrated cellulose fibers (HC-HCV), carried out in a nitrogen atmosphere according to the following temperature-deformation profile:

Pyrolysis is carried out in 8 temperature zones of a high-temperature pyrolysis unit (UHP), in which all temperature zones are separated and have a length of about 2 meters, allowing deformation from (-40%) to (+ 45%).

The next technological stage of HC-GCV production, leading to the achievement of the technical result, is carbonization, which is carried out at temperatures (1000-1100) ° C in a nitrogen atmosphere. Carrying out the above stage separately from pyrolysis is carried out in order to remove pyrolysis products from the surface of the hydrated cellulose threads, remaining after the completion of the previous technological stage. Heat treatment of hydrated cellulose filaments at a temperature of (1000-1100) ° C significantly reduces the content of volatile products released during graphitization, thereby increasing the service life of the graphitization furnace heaters.

The final high-temperature stage of the technological process of obtaining HC-GCV-graphitization is carried out in a nitrogen atmosphere at temperatures (2200-2500) ° C, providing increased physical and mechanical characteristics and thermophysical indicators.

To obtain carbon fiber materials of various textile structures, hydrate cellulose threads are used, impregnated in an aqueous emulsion based on liquid oligomeric resins, and fabrics, ribbons, knitted structures, felt, unidirectional material are made on textile equipment. The above textile materials are sequentially processed at the following technological stages:

1. Thermorelaxation;

2. Pyrolysis;

3. Carbonation;

4. Graphitization.

The claimed method for producing carbon fibers from cellulose hydrate and materials based on them is illustrated by the following examples:

Example 1. Viscose industrial yarn (VTN) (hydrated cellulose yarn obtained by the viscose method) with a linear density of 195 tex is impregnated in a zero strain mode in a 10% aqueous emulsion VE-ABV made on the basis of an oligomeric resin with a silanol group content of 13.4% ... The thermal relaxation stage is carried out at a temperature of 180 ° C in the free shrinkage mode. The technological stage-pyrolysis is carried out at the following temperature-deformation mode:

Table No. 1, zone V

- thread deformation (-5) - (- 10)%;

- carbonation at T = 1000 ° C;

- graphitization at T = 2200 ° C with a deformation of 0%.

The resulting carbon fiber has a relative breaking load of 33.1 gf / tex, the coefficient of variation of the relative breaking load is 18.3%.

Example 2. A hydrated cellulose thread obtained by direct dissolution of cellulose, linear density 184 tex, is impregnated in a zero strain mode in a 10% aqueous emulsion of VE-ABV, made on the basis of an oligomeric resin with a silanol group content of 9.32%. Thermorelaxation is carried out at a temperature of 200 ° C in free shrinkage mode.

The technological stage of pyrolysis is carried out at the following temperature-deformation mode:

Table No. 1, zone V

- thread deformation (-5) - (- 10)%;

- carbonation at T = 1050 ° C;

- graphitization at T = 2300 ° C with a deformation of 0%.

The obtained carbon fiber has a relative breaking load of 33.5 gf / tex, the coefficient of variation of the relative breaking load is 18.6%.

Example 3. A twill weave fabric made from VTN, processed according to example 1, is subjected to heat treatment and deformation at the following technological stages:

1. Thermorelaxation, at a temperature of 190 ° C in free shrinkage mode;

2. Pyrolysis, table No. 1, zone V:

- thread deformation (-25)%;

- carbonation at T = 1100 ° C;

- graphitization at Т = 2250 ° С with a deformation of 0%.

The resulting carbon fabric has the following characteristics:

- The breaking load on a 5 cm strip is 198 kg, the coefficient of variation of the relative breaking load is 18.3%.

Example 4. A twill weave fabric made from BTN, treated according to example 2, is subjected to heat treatment and deformation at technological stages similar to example 3.

The resulting carbon fabric has the following characteristics:

- The breaking load on a strip of 5 cm is 205 kg, the coefficient of variation of the relative breaking load is 19.5%.

Example 5. Viscose knitted fabric, knitted from VTN, treated according to example 1, is subjected to heat treatment and deformation according to example 3 with a final graphitization temperature of 2400 ° C.

The resulting carbon knitted fabric has the following technical characteristics:

- The breaking load on a strip of 5 cm is 195 kg, the coefficient of variation of the relative breaking load is 19.8%.

Example 6. Knitted fabric made from hydrated cellulose yarn obtained by direct dissolution of cellulose and processed according to example 2 is subjected to heat treatment and deformation at all technological stages similar to example 3, with a final graphitization temperature of 2500 ° C.

The resulting carbon knitted fabric has the following characteristics:

- The breaking load on a strip of 5 cm is 210 kg, the coefficient of variation of the relative breaking load is 19.6%.

Example 7. Viscose unidirectional material obtained from VTH treated according to example 1 is subjected to heat treatment and deformation according to example 5 with the amount of deformation at the stage of pyrolysis in the V zone equal to (+25)%. The resulting carbon unidirectional material has the following technical characteristics:

- The relative breaking load of the carbon filament is 56.3 gf / tex, the coefficient of variation of the relative breaking load is 20.3%.

Example 8. A unidirectional material made of cellulose hydrate filament obtained by direct dissolution of cellulose and processed according to example 2 is subjected to heat treatment and deformation in accordance with example 7. The resulting carbon unidirectional material has the following technical characteristics:

- The relative breaking load of the carbon filament is 56.3 gf / tex, the coefficient of variation of the relative breaking load is 20.5%.

Claims (3)

1. A method for producing carbon fiber and materials based on it from an initial cellulosic fibrous material, containing impregnation of an initial cellulosic fibrous material in a liquid-phase organosilicon composition and subsequent heat treatment, including thermal relaxation, pyrolysis, carbonization and graphitation, characterized in that the said method is carried out in continuous mode , and as the initial cellulosic fibrous material, hydrated cellulose threads are used, the impregnation of which is carried out in the mode of zero deformation in an aqueous emulsion of liquid oligomeric resins with a content of silanol groups reaching values from 5% to 15%, while textile materials made from hydrated cellulose threads are heat-treated impregnated in an aqueous emulsion of liquid oligomeric resins, and the pyrolysis is carried out in eight temperature zones, in separate furnaces for each temperature zone in a nitrogen atmosphere when the temperature rises along the zones and the degree of deformation of the thread: in the first zone pyrolysis is carried out at a temperature of 200-220 ° C and a degree of deformation of 0 - (- 5)%, in the second zone - at a temperature of 220-240 ° C and a degree of deformation of 0 - (- 5)%, in the third zone - at a temperature of 250- 270 ° С and the degree of deformation 0 - (- 5)%, in the fourth zone - at a temperature of 270-300 ° С and the degree of deformation 0 - (+ 20)%, in the fifth zone - at a temperature of 310-380 ° С and the degree of deformation (-40) - (+ 45)%, in the sixth zone - at a temperature of 410-540 ° C and a degree of deformation (-5) - (+ 10)%, in the seventh zone - at a temperature of 550-670 ° C and a degree of deformation 0 - (+ 10)%, in the eighth zone - at a temperature of 680-720 ° C and a degree of deformation of 0 - (+ 10)%, while the pyrolysis products are removed from each temperature zone and burned out in a stream of air, and thermal relaxation is carried out in air at a temperature of (180-200) ° C in the free shrinkage mode, carbonization is carried out at a temperature of (1000-1100) ° C, and the graphitization is carried out at a temperature of (2200-2500) ° C with an extraction up to (+ 10%). 2. A method according to claim 1, characterized in that cellulose hydrate yarns obtained by the viscose method or by the method of direct dissolution of cellulose are used. 3. A method according to claim 1 or 2, characterized in that the textile materials are ribbons, fabrics, threads, knitwear, felt, unidirectional material.