Method of producing carbon fibre materials from viscose fibres

FIELD: chemistry.

SUBSTANCE: method involves treating viscose fibre material with pyrolysis catalysts, heating to carbonisation temperature and subsequent graphitation to temperature of 3000°C in an inert medium. Carbonisation is preceded by preparation of precursor by preliminary washing of the starting material with water and/or 5-10% sodium hyposulphite solution with heating and drying, and/or ionising irradiation with a beam of fast electrons during transportation through the irradiation chamber of an electron accelerator, and/or warm-wet synthesis of a complex catalyst on the surface of viscose fibres and in the pore system thereof in boiling 10-20% aqueous ammonium chloride solution and with addition of diammonium phosphate in ratio of 0.5-4.0, followed by steaming in hot steam and final ventilated drying with constant transportation, which enables to deposit the catalyst in form of an amorphous film.

EFFECT: high stability of the process of carbonising viscose fibre material and improved physical and mechanical properties of the obtained carbon material.

6 cl, 7 dwg, 1 tbl, 12 ex

 

The alleged invention relates to chemical technology, and in particular to methods for the production of carbon materials in the form of threads, wire harnesses, belts, fabrics, felts, etc. by thermochemical processing of viscose fibres. The obtained carbon fibrous materials are used as reinforcing fillers composites with polymer, carbon, ceramic and metal matrices for various purposes, insulation of high-temperature thermal equipment, flexible heaters, electrodes for electrolytic processes, filters, aggressive gases, liquids and melts at high temperatures, in the manufacture of the sports goods in medicine.

A method of obtaining UVM [1] impregnation of the original cellulosic fibrous materials (textiles, wool, fine fibers) with an aqueous solution of catalytic compounds, drying, heat treatment in the presence of the introduced catalyst. As the catalyst used for 18.5-29% aqueous solution containing hydroalcoholic ammonium 5-10 wt.%, ammonium chloride 3-12 wt.%, sodium chloride 1-7 wt.%. The content of the catalyst-impregnated material is 15-30 wt.%. Before drying the impregnated cellulosic fibrous material can withstand 15-60 min at 80-100°C, 100%relative humidity in the atmosphere, formed the ri heating the impregnated fibers. Next cellulosic fibrous material is dried at a temperature of 90-100°C and thermoablative in a protective atmosphere (nitrogen, argon, methane). Heat treatment is carried out before any temperature in the range 240-2800°C continuously or stop the process at any stage. Received UVM used independently or subjected to secondary heat treatment to higher temperatures (350-3000°C). The temperature of the secondary firing must be higher than the temperature of the primary heat treatment is not less than 100°C. In this way we obtain a carbonized and graphitized materials used as fillers for plastics, reinforcing elements, materials for high temperature insulation.

The disadvantages of this method are the instability of the process of obtaining UVM, the use of highly concentrated solutions of catalyst (up to 29 wt.%) when the deposition on the source precursors of large quantities of catalyst (15-35 wt.%) to obtain UVM, processed at high temperatures with satisfactory physico-chemical characteristics. Compounds included in the composition of the catalytic mixture, namely sodium chloride, accelerating processes of Chemometrics fiber during heat treatment even in an inert atmosphere and in the presence of activating agents such as water vapor or carbon dioxide gas, p is avodat to the complete destruction of the fiber, that does not allow, including activated (sorption-active) carbon materials with satisfactory strength.

The known method for the production of carbon fibrous materials [2], including the processing of cellulosic material 10-19%aqueous solution of the catalyst is a mixture of ammonium chloride with synergist - urea or orthoborate ammonium content of the catalyst on the fiber 5-20%, with subsequent heat treatment in air and in inert atmosphere with a gradual temperature increase. The treatment machine directly cellulosic material, not containing organosilicon compound. Thermal processing of materials is carried out in an atmosphere of air from 20 to 95±5°C in an inert environment from 95±5 to 450-3000°C.

The obtained carbon materials after heat treatment in an inert gas to a temperature not less than 450°C is subjected to additional heat treatment at a temperature of 750-900°C in the environment of an activating agent in order to obtain the sorption-active carbon materials.

This method according to the distinctive features closest to the proposed technical solution and, therefore, selected as a prototype.

The method of obtaining fibrous material of the prototype has the disadvantage that, as similar to the one manifested in the instability process, the carbon is saved, and as a result, obtained on the basis of the carbon fibrous materials are characterized by low physical and mechanical properties.

The problem of producing carbon fibers from rayon cord fibers caused by the characteristics of the chemical structure of cellulose, which make it more difficult technologically simple transformation into a carbon material. Thermochemical transformation of viscose fibers in carbon is the result of a multistage strictly regulated process. This is because due to the presence of acetylenic relations (oxygen bridges) between the links of the main chain, and within parts of the carbonisation complete depolymerization of cellulose macromolecules with breaking these bonds so that the reacting system withdrew atoms of oxygen, preventing leakage in carbon pyrolization fibrous residue of the condensation processes in the formation of graphite-like carbon structure.

In addition, rayon cord fibers have heterophase structure, i.e. the presence of fiber crystalline and amorphous regions. Structural heterogenety, as shown by the experimental results, the most significant negative factor in the process of obtaining carbon fibers with stable physico-mehanicheskaya. The structure of viscose fibres is very variable and depends on many factors numerous stages of their production process. Strict identification viscose fibers, even one batch of production, can not be practically as can vary substantially in their structure-sensitive properties. This reduces the stability of the carbonization process and the strength obtained after the graphitization of the carbon fibers.

Structural instability of viscose fibers laid at different stages of the production process. However, the forming operations, deposition and plastification drawing the fibers occurs in the stress-strain state, making a strong contribution to the instability of the carbonization process.

The purpose of the proposed technical solution is to increase the stability of the carbonization process of viscose fiber and physico-mechanical properties of the obtained carbon fibers. This goal is achieved due to the fact that in the known method for the production of carbon fibrous materials, including processing of viscose fiber material catalysts for pyrolysis, heat treatment by heating to a temperature of carbonization and subsequent gravity to a temperature of 3000°C in an inert environment, in accordance with the claimed invention, before Carbo is izala carry out the preparation of the precursor(the Term "precursor of carbon fiber material" assigned viscose fiber material, subjected to all operations finish and fully prepared for the carbonization process. This indicates that this material can only be used for its intended purpose, namely to obtain a carbon fiber material.) carbon fiber material by pre-washing of the source material with water and/or (5-10)%-s ' solution of hyposulphite of sodium by heating and drying, and then ionizing irradiation by a beam of fast electrons during transportation through the camera irradiation of the electron accelerator and/or heat and humidity synthesis of complex catalyst on the surface of viscose fibers and porous his system in 10-20%boiling aqueous solution containing ammonium chloride and with the addition of diammonium phosphate in a ratio of from 0.5 to 4.0 with subsequent steaming hot couple and final vented dryer with continuous transportation, providing the deposition of the catalyst in the form of an amorphous film. Pre-washing is carried out in water at a temperature of (20 to 100)°C for (10-20) minutes and/or within (15-45) minutes (5-10)%aqueous solution of hyposulphite of sodium at a temperature (80-100°C)and drying over (20-30) minutes at a temperature of 90-110°C in a ventilated drying chamber.

Ionizing irradiation by a beam of fast electrons during transportation through the camera exposed the Oia electron accelerator spend with speed (1-4) m/min, the beam current (1-3) µα and energy (0,5-0,7) Mew. The heat and humidity synthesis of complex catalyst and spend (10-20)%water containing ammonium chloride with the addition of diammonium phosphate in a ratio of from 0.5 to 4.0 at a temperature (80-100°C)for 20 to 45 minutes, and the steaming viscose fiber material should be performed within (10-15) minutes at a temperature of (90-130°C in a hot pair, removing the steam and products of drying of the drying chamber through the pneumatic resistance in the form of a gas-permeable barriers. This final drying of the precursor is carried out in a ventilated chamber at a temperature (100-130°C)until constant weight.

The primary action of the preparation of the precursor, the authors propose a washing fibrous material in water at a temperature of (20 to 100)°C for (10-20) minutes and/or in (5-10)%aqueous solution of sodium thiosulfate at a temperature (80-100°C)and drying over (20-30) minutes at a temperature of 90-110°C in a ventilated drying chamber.

Technical feasibility of conducting the primary operations of washing viscose material is determined by the fact that viscose fibers in the process of getting treated with various substances modifier, which is administered either in a precipitation bath, or in a viscose solution, in addition, on the surface of the molded fibers cause oil and avimanyu drugs how to improve forming the ti fibers, and for improving textile processing into yarns and fabrics. The content of these compounds has not improved processing of viscose fibers in carbon fiber, worsening the conditions of carbonization and reducing the strength properties of graphite fibers.

When stored on the surface of viscose fibers formed a dense layer of keratinization, which hinders the absorption of viscose fibres solution of the original catalyst components.

Increase the temperature to boiling water, which washed viscose material, increases the intensity of the process of washing, helps preliminary relaxation fiber.

The use of sodium thiosulfate based on the fact that the SRT has a low concentration of hydroxyl ions in aqueous solutions, it is virtually Chemometrics viscose fibers, thus has a protective effect against oxidation of macromolecules of cellulose with oxygen dissolved in the water and who is very active in wet swollen fiber. The protective effect of sodium thiosulfate is manifested as a result of its oxidation reaction:

2Na2SO3+3O2→2Na2SO4+3SO2,

thereby reducing the concentration of oxygen in the solution and the oxidative degradation of cellulose, while contributing to a deeper diffusion of moisture in intermolecular what prostranstva.

After treatment in the sodium thiosulfate solution in the viscose fiber there is practically no reduction in the strength characteristics.

The numerical values of the processing parameters in water and aqueous sodium thiosulfate solution was determined experimentally. The increase in temperature processing of viscous material in the water to the boil somewhat improves the results of carbonization. In the case of treatment in an aqueous solution of sodium thiosulfate technical effect of improving the strength of carbon fiber is observed only in the processing of viscose fiber material in the boiling solution.

In the processing of viscose fibers in water and the washing effect seen little, if the operation takes less than 10 minutes Increase the processing time more than 20 minutes does not increase the achieved effect. Drying after treatment in water at a temperature (90-110°C)in a ventilated chamber favors the passage of relaxation processes, the shrinkage of the material.

At wash viscose material in the sodium thiosulfate solution with a concentration of less than 5% improvement in the properties of the fiber after carbonisation and graphitisation is not observed. This effect appears and increases with increasing concentration of sodium thiosulfate in water from 5% to 10%. The increase in the concentration of more than 20% not only leads to improved properties of produced of plastics technology : turning & is the breaking of the fibers, on the contrary, there is a tendency to decrease in strength properties.

In the process of cleaning the moisture penetrates into the pores and intermolecular space, causing swelling and plasticization of viscose fibers. Deep diffusion of moisture in the intermolecular space - kinetic process. As a result of the experiments revealed the dependence of the temperature of maximum rate of thermal decomposition of the viscose fiber during heat from the duration of washing in a solution of sodium thiosulfate. This dependence is exponential in nature. The minimum temperature intensive degradation rate is observed after washing for 15 minutes to Further increase the duration up to 30 min did not increase the observed effect. Therefore, the interval duration from 15 to 45 min is taken as the optimum. This is especially appropriate, since the operation of the washing energy-intensive process, so increasing the duration leads to additional costs.

Quick drying viscose material in a ventilated chamber at a temperature (90-110°C. after washing in a solution of sodium thiosulfate as necessary, and after washing in water.

A distinctive feature of the proposed method is that viscose fiber material is subjected to ionizing irradiation by a beam of fast electrons during transport the implement through the camera irradiation of electron accelerator speeds (1-4) m/min, the current of the electron beam (1-3) µα and energy (0,5-0,7) Mew.

The specified distinguished action perform to achieve the most rapid and effective relaxation of residual internal stresses in the viscose fiber and averaging parameters of its structure. The effectiveness of this impact is due to the fact that pulp and hydrocellulose, in particular, are characterized by low radiation resistance. Radiation-chemical effects of irradiation are determined by the chemical structure of the polymer and the integral dose the absorbed energy. In a series of 14-and the most resistant polymers, if they are placed in the sequence of decreasing radiation resistance depending on the power relations between the major functional groups in the main polymer chain, pulp occupies the 12th place. Therefore, even a very small cumulative doses of ionizing radiation cause in the structure of the viscose fibers major structural changes, the qualitative trend which is averaging structural characteristics of ordered and amorphous regions in the fiber. In addition to reducing the degree of orientation of the macromolecules in the fiber, there is also a spontaneous ordering of the individual elements of the structure together with the formation in the radiolysis of active polymer macroradicals. Therefore, led the increases the degree of microheterogeneity structure due to the formation of new structural microplasma and new interfaces between more ordered and less ordered structure formations. The increase in the number of interfaces between structural formations accompanied by an increase in the number of elementary lesions of the stress in which arises the reaction of thermal decomposition at lower temperatures. When the integral value of the stress-strain state of the fiber becomes far less than the amount of VAT fibers before irradiation. The increase in the number of foci elemental stresses on the boundaries of structural domains with different degree of ordering of sections of cellulose macromolecules leads to the reaction of thermal decomposition at the same time in a larger number of points in the volume of the reacting system, there is the effect of increasing mekranoti of the pyrolysis process in the elementary volume of the fiber. Therefore, there is a reduction of tension in the initial period of pyrolysis when polihrono the process and reduce the stability of the carbonization process. The degree of polihrono thermal decomposition of the carbonisation viscose fibers irradiated by a beam of fast electrons is significantly reduced. In the same way decreases the duration of the reaction of thermal decomposition of cellulose, as the pyrolysis significantly larger number of structural areas proceeds simultaneously and not in consecutive intervals. The lower level who is causig during pyrolysis of stress contributes to identical conditions of formation of carbon structures in all elementary volume carbonization when the current temperature of viscose fibers. Experimental data show that the strength of carbon graphite fibers tends to increase, if in the process of obtaining the decomposition of viscose fibers during carbonization proceeds on monochronous mechanism.

Recommended settings ionizing radiation viscose fibres determined empirically. Compliance ensures optimal-sufficient as relaxation and destructive rearrangements in irradiated fiber. Irradiation of viscose fibers according to the mode with lower values in comparison with those that have no visible effect, and excess or reduced rate transportation leads to significant radiation-induced destruction (radiolysis) of the fiber, resulting in lost the possibility of its use as a feedstock for the production of carbon fiber.

In accordance with the following distinguishing feature of the proposed invention the heat and humidity synthesis of complex catalyst on the surface of the source fiber and porous his system is carried out in (10-20)%boiling aqueous solution containing ammonium chloride with the addition of diammonium phosphate in a ratio of from 0.5 to 4.0 with subsequent steaming hot couple and final vented dryer with continuous transportation, ensuring the sponding deposition of the catalyst in the form of an amorphous film.

When evaluating the performance featured the distinctive steps must be borne in mind that in the technology of production of carbon-based fibers of viscose fibers is widely recognized as a provision stating that a strong carbon fiber cannot be obtained if the pyrolysis of viscose fibres is carried out without the use of catalysts of reactions of thermal decomposition of cellulose and the formation of a carbon fibre structure. It should be stated and the fact that there is currently no generally accepted theory-based approach to the development of a catalyst thermochemical transformations of viscose fibers in the carbon fiber. Therefore, in this technical proposal, development of a catalyst was carried out in the course of experimental investigations of the processes of carbonisation and graphitisation of viscose fiber. Was developed set of requirements which had to answer, select a component of the catalyst:

- each component must have some ability to increase the intensity of pyrolysis viscose fibers, to reduce the onset temperature of thermal decomposition and to reduce the maximum mass loss rate, that is, to prevent unregulated thermal decomposition of cellulose, which greatly reduced the yield by weight of carbon fiber and it became etait stiffness, fragility and very low strength;

in the catalyst composition selected components should enhance the action of each other, i.e. create a synergistic effect of interaction with carbonicum fiber;

- the initial temperature of thermal decomposition of at least one of the catalyst components must be below the temperature of the beginning of decomposition of the viscose fibers;

- the catalytic composition on the temperature intervals own thermal transformations should be adequate enough intervals thermal transformations of viscose fibers.

These requirements meet the compounds of Halogens and phosphorus as candidate components of the complex catalyst. Most are active catalytic compounds, including halogenated compounds. When thermal and thermooxidative degradation of halogenated compounds decompose with the formation of halogen, halogen-hydrogens and halogenoalkane hydrocarbon particles, which are catalysts of coke formation. Therefore, the introduction of the catalyst Halogens and halogenated compounds, along with the acceleration of thermal pyrolysis, viscose fiber stimulates the formation of carbonaceous substances, as, for example, chlorine, as representative of the Halogens, is the catalyst reaction in which a significant portion is released during pyrolysis WITH consumed in the formation of carbon. The formation of carbon is explained by the activity of the Halogens and the ease of adsorption is carried by the surface of the fiber.

Generally speaking, the composition of the catalyst carbonization must have a primary accelerator destruction, activator or synergist and stabilizer. The number of components of the catalytic composition providing the above effects, up to 5 or even more compounds. In the described similar number of components reaches 3-H. However, the increase in the number of components in the catalyst increases its selective action: it is effective only for the specific fibers or even structural elements of the fiber. This feature of complex catalysts increases the instability properties of the obtained carbon fibers, that is counterproductive. During the experiments tested a multicomponent catalysts did not show reproducible positive results.

The main investigations were carried out in the direction of creating a more simple catalysts, which are in development authors contain the primary accelerator destruction and amplifying its effect is additive accelerator destruction.

According to the results of the experiments, a simple catalyst which show great versatility when subjected to pyrolysis various viscose fibres. Determined that compounds containing phosphorus, as independently good catalysts, greatly enhance the action of the main catalysts - halogenated compounds and, very importantly, perform the role of stabilizers, slow removal of halides from the reaction zone. This is because in the process of joint terupravleniya halogenated and phosphorus-containing compounds halides of phosphorus, which also exhibit the properties of active catalysts for the formation of carbonaceous matter.

Installed so that the synergism of halogen-containing and phosphorus-containing components of the catalytic composition manifests itself under certain optimal concentration and quantitative ratios of the carbonisation specific viscose fibers.

As a representative of halogenated compounds selected ammonium chloride, and representative phosphorus-containing compounds, diammonium phosphate. These compounds have good solubility and compatibility in aqueous solution.

On the basis of the experimental data were determined intervals varying the concentration of the solution and the ratio by weight of ammonium chloride, diammonium phosphate.

Conducting heat and humidity synthesis (FAS) of the catalyst on the fiber surface and in the volume of his Pori is the system is the interaction of chemicals among themselves, with the active groups of the macromolecules of cellulose and has a significant impact on the structure of viscose fibres. The manifestation of this impact is the additional relaxation of the stress-strain state, remaining in the fiber after the previous operations of washing and exposure, as well as in the deeper structural change, which for some types of fibers are sufficient to increase the strength of the obtained carbon fibers. In essence, this phenomenon is due to the fact that the parameters of the structural elements of the fibers and their non-equilibrium state is very sensitive to physical and chemical processes in fuel assemblies of the catalyst followed by steaming and drying viscose fibers. As in the formation of supramolecular structures in subsequent operations of preparation of the precursor great role is played by the energy characteristics of macromolecules: the level of interatomic and intermolecular interactions and their own flexibility macrocephaly. Macromolecule cellulose has a high rigidity. It promotes self-regulation patterns in conditions of humidity and chemical effects with increasing moisture content. The result is an increase in the size of existing regular formations by structuring resistivity is at with them amorphous areas, as well as the emergence of new structures with new boundaries, leading to an increase in the number of hotspots in the elementary volume of the fiber. The increase of tensions in which the excited reaction of destruction, as already mentioned in the description of such a transformation as a result of irradiation, is a condition of increasing the degree of black destruction viscose fibers in the volume of the reacting system, which has a positive effect on the formation of carbon fibre structure during carbonization.

Conducting FA catalyst in the presence of viscose fibers at elevated temperature (boiling point) of an integrated solution enhances the interaction of the source of catalyst components among themselves and with the active groups of the cellulose molecules, and increases the speed and depth of the absorption solution in the capillaries of the porous system of the fiber and contributes to its penetration in the intermolecular space, i.e. increases the degree of volumetric saturation of the fiber with a solution of a catalyst, bringing it into direct contact with the cellulose molecules. This factor has a positive effect on thermal decomposition reaction, as through direct contact with macromolecules in the fiber volume, the catalyst activates the reaction pirol is for pulp when the heating temperature is lower than the temperature of the beginning of its own decomposition.

The synthesis of the catalyst is a kinetic process. The mechanism of synthesis includes, according to the authors, at least three stages, which mainly occur sequentially. However, it should be assumed that the beginning and subsequent completion of the previous stages run all in parallel. The fourth stage begins and ends with the steaming and the final drying of the precursor. In the beginning of the first stage for up to 15 min hydrolysis of diammonium phosphate as salts formed by weak acid and weak base, which is more intense at higher temperatures the boiling comprehensive solution.

In the second stage dominated by the process of chelation, in which the complexing agents is chlorine. The second stage of the synthesis provides the condition for the co-deposition of salts of ammonium chloride and hydrolysis products of diammonium phosphate. The third stage of the synthesis is manifested in the interaction of ions of the catalyst active side groups of the cellulose molecules as diffusion of the solution into the porous system and intermolecular space viscose fibers. The final stage of synthesis of the catalyst takes place at the steaming and the final drying of the precursor. The dominant process is a joint precipitation of the product is the interaction of the catalyst components between themselves and the macromolecules of cellulose on the surface of the fiber in the form of an amorphous film.

Complete the synthesis of the catalyst during the preparation of the precursor surgery steaming and final drying viscose fibers distinctive steps which consist in the fact that the duration of steaming hot pair is (10-15) minutes at a temperature of (90-130°C), the removal of steam and products of evaporation from the camera that you are carrying out through the pneumatic resistance in the form of a gas-permeable barrier, and the final drying of the precursor is carried out in a ventilated chamber to a constant weight at a temperature (100-130)°C.

Holding steaming in the indicated temperature interval provides the necessary conditions of deposition of the catalyst in the steam system of the fiber, where he was taken, in the form of a solution. The fact that in normal ventilated drying occurs migration of the solution through the capillaries of the porous system of fiber volume to its surface, where evaporation of water and the deposition of the catalyst in the form of crystals. Based on experimental observations, we can assume the existence of trends sequential crystallization of the components on the surface of the fiber, when this process takes place in conditions of a ventilated drying. When carbonization of the fibers with the surface of precipitated catalyst in the form of crystals does not occur forming a carbon structure that provides necessary so ostrye characteristics of the obtained graphitized carbon fibers. By heating the fiber in an atmosphere of hot vapor of the solvent - water in the capillaries, pores and intermolecular spaces, boils and moves to the surface of the fiber in the form of steam, and the components of the catalyst are deposited simultaneously in a porous system and on the surface of the fiber in the form of an amorphous film. This effect can be observed visually, as a kind of fibrous materials with deposited catalyst in the form of crystals and form an amorphous film is very different. Carbonization of the precursor with a catalyst deposited as an amorphous film, allows to obtain a graphitized carbon fiber with high strength.

The interval of variation of temperature steaming viscose fibers in range (90-130°C)determined experimentally. Lowering the temperature below 90°C does not cause boiling of the solution in the capillaries, and increased more than 130°C leads to degradation of the material.

Final ventilated drying the precursor at a temperature (100-130°C)is conducted to remove excess moisture of the material, which affects the process of carbonization. Drying in the specified temperature range of the heating does not cause recrystallization of the catalyst, deposited in the form of a film, and does not reduce the strength of the final product.

The removal of steam and products of steaming VI is koznogo material from the drying chamber through the pneumatic resistance, in the form of a gas-permeable barriers, it is advisable to supply the steam to escape and products steaming across the entire cross-sectional area of the channel in which the transported material, to prevent condensation of steam and drip condensation on the steamed material, and to create in the chamber steaming small excess pressure of hot steam that would create a consistent environment throughout the volume of the chamber.

Thus, only experimentally installed a set of ongoing thermal effects on the source of viscose fiber in obtaining precursor, which cause deep polymorphic transformation with catalyst pyrolysis increases the stability of the carbonization process and physical-mechanical properties of the obtained carbon fibers compared with the characteristics of the carbon fibers by means of a prototype and similar.

The essence of the proposed invention is illustrated by examples of its execution.

All of the examples use standard equipment; to determine the physical and mechanical properties of the obtained fibers were obtained using standard techniques and equipment.

Specific example

Viscose fiber based material viscose (cord) technical threads 192 Tex TL6-12-0020456-7-92 in the form of bundles or fabrics of different patterns, or neck the aqueous material is pre-washed in water municipal water supply at a temperature of (20 to 100)°C for (10-20)minutes or (5-10)%solution of hyposulphite of sodium GOST 244-76 at temperatures (80-100°C)for 20 to 45)minutes

When used as a feedstock viscose fiber material in the form of fabric and non-woven material separate pieces sewn together in a continuous ribbon viscose technical thread.

Water is poured into a wash tank a through-type and heated to a predetermined temperature.

The source material in the form of bundles or an endless belt continuously load and continuously removed from the wash tank. The necessary duration of washing provide the number loaded into the container material and the speed of its transportation through a wash tank. At the output of a wash capacity of the washed material is passed through plusone rolls for squeezing excess moisture and transported through the drying and tentering machine, the drying duration in which regulate a number of material and speed of transportation. The washing operation is carried out with the provision of shrinkage of the material.

In the case of viscose washing fibrous material in a solution of hyposulphite of sodium in a separate container equipped with a heating to the boiling point of water, prepare a solution in water of sodium hyposulphite and serve it in a wash tank. The remaining operations of the washing implement as well as when washing in the water.

Dried and wound on drums viscose material miss h is rez camera irradiation of the electron accelerator of the type of EBV-1 speeds (1-4)m/min, the beam current (1-3) µα and energy (0,5-0,7) Mew and take on the drum.

The operation of irradiation viscose material may be effected without prior washing in water or in a solution of sodium thiosulfate.

To conduct heat and humidity synthesis of complex catalyst previously prepared solution of ammonium chloride GOST 2210-73 with the addition of diammonium phosphate GOST 8515-75 in the ratio of 0.5:4.0 water urban water concentration (10-20)% wt., bring it to boil and serve in otvarennuyu the tank, which is continuously loaded and continuously unloaded washed, dried and/or irradiated viscose fiber material. The temperature of the integrated solution in otvorotnoj capacity is maintained at a level (80-100)°C. the duration of the synthesis of complex catalyst depends on the number located in the tank of viscous material and the speed of its transportation and regulated in the range of 20 to 45) minutes

After treatment in boiling comprehensive solution chemicals viscose material is passed through plusone rolls for squeezing excess solution and served during continuous transportation in propanol chamber of the drying unit standard design for finishing textile industry within (10-15) minutes at a temperature of (90-130°C), removing the steam and products of steaming fibers the material from the chamber through the pneumatic resistance in the form of a gas-permeable barriers, for example, canvas fabric with a density of yarns in the warp and weft of not more than 100 threads per 10 cm and a density of threads 192 Tex. The duration of the steaming regulate the amount of material in propanol the camera and the speed of its continuous transportation. Final drying the steamed material is carried out in a ventilated drying chamber at a temperature (100-130°C)to constant weight under continuous transportation, the duration of which also regulate how and when steaming.

Operation heat and humidity synthesis catalyst on the surface of the material may be subjected to a source of viscose fiber without washing and exposure.

Past all the preparatory stage before carbonization: washing, drying, irradiation, heat and humidity synthesis catalyst on the surface of the fibers, steaming and final drying or separate stages: exposure + synthesis catalyst viscose fiber precursor carbon fiber is fed to the carbonization and gravity. Hydration of the precursor after the final drying is not valid.

This is followed by carbonization of the precursor and gravity carbonized fibrous material.

The optimal values of process parameters for the production of carbon fibers were installed in a pilot study with a large number of tested variants. Rez is ltati experiments were statistically processed and built graphics according to the strength of the resulting carbonized and graphitized materials from changes in the parameters studied, which have been defined in the intervals of their optimal values.

In the conducted experiments the variation has been analyzed parameter, and the preparation of the precursor was carried out in the same mode settings: washing in water at a temperature of 100°C or in 10%solution of sodium thiosulfate at a temperature of 100°C, drying at 100°C, irradiation with fast electrons at the beam current of 3 µa, energy 0.7 Mew, the speed of transportation of 2 m/min, the ratio of ammonium chloride, diammonium phosphate 3:2, the concentration of the solution during the synthesis of the catalyst is 17%, the duration of the synthesis of 30 min, steaming - 100°C, drying - 100°C. These values are taken as the optimal and determined by special experiments.

In the analysis of experimental data the experiments in which the obtained graphite yarn had a strength above 1000 HS/thread, was assessed as positive.

The strength of the carbonized filaments in all experiments exceeds the strength of graphite threads, but changing it does not always follow the character changes in the strength of graphite depending on the change of the numerical values of the investigated process parameters. Therefore, the change of properties of carbonized filaments were not taken into account when determining the optimal parameters.

1, 2, 3 shows the graphs characterizing the parameters of the tentatively the satisfactory cleaning of the investigated viscose fiber material: 1 - the effect of concentration of sodium thiosulfate solution at wash viscose fibers for strength carbon graphite filaments; 2 - the effect of temperature 10%aqueous sodium thiosulfate solution (1) and water (2) at wash viscose fibers on the strength of graphite fiber viscose fiber without washing; Fig.3 - effect of drying temperature viscose fiber after washing in water (1) and 10%aqueous sodium thiosulfate solution (2) at a temperature of 100°C (boiling water and solution) for 30 min on the strength of the resulting graphite fibers.

According to Fig.1, the higher strength of graphite carbon can be achieved if the wash is the source of viscose fibers to hold a 10%aqueous sodium thiosulfate solution at the boiling temperature of the solution (90-100°C) (according to Fig.2). Along the curve 2 in figure 1 shows that increasing the strength of the graphite filaments occurs with retention of a wash solution, ranging from 5%, and continues until the concentration of 10%. The optimal value of the concentration of the sodium thiosulfate solution is 10%. Increasing concentrations of more than 20%, does not increase the strength of the carbon fibers, and the concentration of the solution is less than 5%, no change strength lower than the strength obtained at 10%.

According to the data presented in figure 2, when using the original what about the fiber without washing get very fragile carbon fiber. Washing in water (curve 2) increases the strength of carbon fiber, but the resulting strength is still not enough, however, washing in water at boiling significantly reduces the content of various substances on the surface of the fiber and thereby improves the quality of the other liquid operations by reducing pollution working solutions.

A more significant increase in the strength of carbon fibers is observed, if the shaded viscose fibers was carried out in 10%aqueous sodium thiosulfate solution at the boiling temperature of the solution (80-100°C) (curve 1 in figure 2). This interval of temperature washing is recommended when implementing the proposed method to obtain carbon fiber.

From the analysis of the obtained results it follows that the exception drying material, washed in sodium thiosulfate solution, reduces the strength of the resulting graphite fiber twice. The drying temperature of the fiber after washing in water has little effect on the change in the strength of graphite filaments. The best result in this series of experiments obtained by drying the washed in a solution of sodium thiosulfate viscose fibers at a temperature of 100°C. the Increase in drying temperature above 110°C gives unstable results in strength graphite fibers, and drying the material below 80°C the strength of graphite fibers is reduced. P is to vary the temperature of the drying viscose fiber after washing in water and in sodium thiosulfate solution recommended temperature range (80-110)°C.

Table 1 presents the results of experiments (examples 1-12 specific performance) to determine the optimal irradiation parameters viscose fibers.

Table 1
Influence of the mode of exposure viscose fibers on the strength of graphite threads
№ p/pStage preparation of precursorThe exposure modeThe strength of graphite threads
The current of the electron beamThe beam energyThe speed of transportation
µαMewm/minHS/thread
1.Washing in water10,511300
2.20,621250
3.3 0,741400
4.50,70,5300
5.Washing in a solution TSN10,511350
6.20,621600
7.30,741480
8.50,70,5380
9.The original fiber without washing10,511200
10.20,621450
11.3,7 41580
12.50,70,5309

Data analysis table 1 allows us to conclude that irradiation of viscose fibres subjected to washing in water and in sodium thiosulfate solution, and without washing, provides conditions for obtaining graphite filaments of high strength.

Irradiation of viscose material mode with settings that differ from the recommended, dramatically reduces the strength of the resulting graphite fibers.

To determine the optimum relationship of the source components of a comprehensive solution for the synthesis of catalyst pyrolysis viscose fibers held a special series of experiments, the results of which are presented the graphs in Fig.4. Fig.4 shows the effect of mass ratio of initial components of a comprehensive solution of the catalyst is ammonium chloride (HA), diammonium phosphate (DAP) on the strength of carbon fibers (1 - carbonized filaments; 2 - graphite filament).

The most durable graphite fibers were obtained when a solution of ammonium chloride was additionally introduced, diammonium phosphate in such a quantity that the ratio of ammonium chloride, diammonium FOSFA is and was equal to 1.5. The most similar values of the relations to the specified ratio of 1.5 are enclosed in the interval from 0.5 to 4.0, in which the strength value obtained graphite filaments is sufficient to meet the fibers requirements. Therefore, the interval of values of the mass ratio of ammonium chloride, diammonium phosphate from 0.5 to 4.0 recommended when carrying out the synthesis of the catalyst in the production of carbon fibers of the proposed method.

Figure 5 presents the results of a comprehensive study of the effect of duration of washing in a solution of sodium thiosulfate on the temperature change of the maximum speed of thermal decomposition washed and dried viscose fiber (curve 1) and duration of the synthesis catalyst strength carbon fibers (curves 2, 3). Fig.5 shows the effect of duration of operation of washing in a 10%solution of sodium thiosulfate at a temperature of maximum rate of thermal decomposition of the viscose fiber (1) and the operation of the synthesis catalyst (2, 3) on the strength of carbon fibers (2 - graphite filament; 3 - carbonized thread).

Based on the analysis of the graphs presented in figure 5, we can conclude the following. An effective mechanism of synthesis catalyst viscose fibers, described previously, is in agreement with the curve of 1 changes the maximum temperature of the IC is to grow the destruction depending on the duration of the operations of washing in a solution of sodium thiosulfate in the initial stage of the operation of washing (with a duration up to 15 minutes), the decrease of the temperature of the maximum speed thermal decomposition.

This indicates the initial changes in the fibre structure (restructuring texture and fibrils) at elevated temperature in the presence of moisture and chemicals. But these initial structural adjustment remain at this level that the synthesis of the catalyst over the same period of time does not significantly increase the strength of graphite fibers (curve 2), and the strength of the carbonized yarn (curve 3) decreases as temperature decreases the maximum speed of thermal fiber (curve 1).

Only since the duration of the synthesis and washing the fibers in a solution of sodium thiosulfate, equal to 10-15 min, is increased and the temperature of maximum degradation rate, and strength of the obtained carbon fibers, which have been observed in the course of performing these operations with increasing duration up to 45 minutes So the interval duration of the operations of washing in a solution of sodium thiosulfate and synthesis catalyst pyrolysis viscose fiber from 20 min to 45 min, defined as optimal. The dependence of the tensile strength of carbon fibers on the concentration of the complex solution of initial components of the catalyst are presented graphically in figure 6. Fig.6 shows the dependence of the tensile strength of graphite filaments on the concentration of the complex solution of the original components is tov catalyst carbonization of viscose fibers.

This dependence has an extreme character. Application of the solution for the synthesis of the catalyst concentration is less than 12 wt.%, as well as more than 20% wt. leads to a significant reduction in the strength of the obtained carbon fibers. Therefore, the interval of values of concentration of a solution of 12 wt.%. up to 20% wt. suggested as optimal.

Figure 7 shows the dependence of the strength of carbon fibers from temperature (1-4) and duration (5) steaming and final drying of the precursor after synthesis of the catalyst (1 - carbonized filaments; 2 - 5 - graphite filaments; 3 - precursor after synthesis catalyst was stored for 24 hours at 20°C in a desiccator, and then was subjected to steaming and final drying; 4 - precursor after synthesis catalyst was stored in air for 6 h, then was subjected to steaming and drying). In the course of the curve 2, the strength of the resulting graphite yarn increases with the temperature steaming and drying. In the temperature range from 90°C to 130°C the strength obtained in the experiment of graphite filaments reaches the maximum value.

In the experiments conducted at higher temperatures steaming recorded the appearance of a clear indication of the beginning of the pyrolysis fiber and fall of the stability properties of graphite filaments. Therefore, the increase of temperature steaming and drying in the above 130°C it would be impractical. Lowering the temperature of the steaming and drying to below 90°C is accompanied by a significant decrease in the strength of graphite fibers, and the strength of carbonized thread is almost no effect.

Specially the experiments showed that the storage of the precursor before steaming and drying in air at a temperature of 20°C has a very adverse effect on the strength of the resulting graphite yarn. The operation of storage of the precursor at room temperature before steaming and drying should be excluded.

In the course of the curve 5 in figure 7 we can conclude that the duration of the steaming and drying did not affect the strength of the resulting graphite yarn as temperature. If the steaming and drying of the precursor is carried out at temperatures above 100°C, the moisture evaporates very quickly, within 2-4 min, however, in addition to physical evaporation occur as the reaction of the chemical interaction of the components of the catalyst with the active groups of cellulose macromolecules and allotropic changes precipitated catalyst. Therefore, in the course of them needed more time, which is plotted in the interval (10-15) minutes At such duration steaming and drying, the resulting graphite yarn characterized by maximum durability.

Sources of information

1. Patent No. 2016146, CL D01F 9/16, op. 15.071994, H. No. 5003016 from 16.07.1991.

2. Patent No. 2231583, CL D01F 9/16, op. 27.06.2004, H. No. 20020085 from 05.11.2002 how.

1. The method of obtaining the carbon fiber material on the basis of viscose fiber material, including processing of viscose fiber material with a solution of compounds which catalyze the reaction of pyrolysis, heat treatment by heating to a temperature of carbonization and subsequent gravity to a temperature of 3000°C in an inert atmosphere, characterized in that before carbonization carry out the preparation of the precursor of carbon fiber material by pre-washing of the source material with water and/or 5-10%solution of hyposulphite of sodium by heating and drying, and/or ionizing irradiation by a beam of fast electrons during transport through the camera irradiation of the electron accelerator and/or heat and humidity synthesis of complex catalyst on the surface of the original fiber and porous his system in 10-20%water boiling solution containing ammonium chloride with the addition of diammonium phosphate in a ratio of from 0.5 to 4.0, followed by steaming in a hot pair and final vented dryer with continuous transportation, providing the deposition of the catalyst in the form of an amorphous film.

2. The method according to claim 1, characterized in that washing produce in water at a temperature of 20-100°C for 10-20 mini/or within 15-45 min at 5-10%aqueous solution of hyposulphite of sodium at a temperature of 80-100°C and dried for 20-30 min at a temperature of 90-110°C in a ventilated drying chamber.

3. The method according to claim 1 or 2, characterized in that the ionizing radiation beam of fast electrons during transportation through the camera irradiation of electron accelerator spend with a speed of 1-4 m/min, the current of the electron beam 1-3 a and energy of 0.5-0.7 Mew.

4. The method according to claim 1 or 2, characterized in that the heat and humidity synthesis of complex catalyst is carried out at a temperature of 80-100°C for 20-45 minutes

5. The method according to claim 1, characterized in that the steaming viscose fiber material carried out directly after the heat and humidity synthesis for 10-15 minutes at a temperature of 90-130°C in a hot pair, removing the steam and products steaming from the drying chamber through the pneumatic resistance in the form of a gas-permeable barrier.

6. The method according to claim 1, wherein the final drying of the precursor is carried out in a ventilated chamber at a temperature of 100-130°C to constant weight.



 

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