BR102015025428A2 - Polyacrylonitrile composition and use thereof - Google Patents

Abstract

Polyacrylonitrile composition and use thereof describes a method which allows the production of polyacrylonitrile (pan) fibers by melting process in spinning extruders by the use of pan compositions with high boiling point and dipolar moment plasticizers such as glycerin and glycerine carbonate. The use of cyclization stabilizers also derived from halogenated glycerine, known as halodridines, and additives derived from glycerine esterification with fatty and phosphoric acids are also described. By removing plasticizers and additives soluble in polar solvents such as water or alcohols, soon after the spinning step, it is possible to produce pan fibers with characteristics similar to those produced by traditional wet spinning processes, widely used in the production of carbon fiber. It is noteworthy that the glycerin used in the pan plasticization can be derived from biodiesel production and does not need to be purified by distillation process.

Description

(54) Title: COMPOSITION OF

POLYACRYLONITRILE AND USE OF THE SAME (51) Int. Cl .: D01F 6/18 (73) Owner (s): CHEMICAL AND METROLOGICAL LABORATORIES QUIMLAB LTDA (72) Inventor (s): NILTON PEREIRA ALVES GRANADO (74) Attorney (s) : ORLANDO DE SOUZA (57) Abstract: COMPOSITION OF

POLYACRYLONITRILLA AND USE OF THE SAME Describes a method that allows the production of polyacrylonitrile fibers (PAN) by fusion process in spinning extruders, using PAN compositions with high boiling point plasticizers and dipolar moment such as glycerin and carbonate glycerin. The use of cyclization stabilizers also derived from halogenated glycerin, known as halodridines, and additives derived from esterification of glycerin with fatty and phosphoric acids are also described. Through the removal of plasticizers and additives soluble in polar solvents such as water or alcohols, soon after the spinning stage, it is possible to produce PAN fibers with characteristics similar to those produced by traditional wet spinning processes, widely used in the production of carbon fiber. It is noteworthy that the glycerin used in the plasticization of PAN can come from the production of biodiesel, not needing to be purified by the distillation process.

PAN + PLASTIFIERS

DEPLASTIFICATION

DRYING

DRAWING

COILING

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POLYACRYLONITRILLA COMPOSITION AND USE OF THE SAME

Field of the invention [001] The present invention privilege patent aims to describe a polyacrylonitrile (PAN) composition suitable for melt spinning and also for its use in the production of carbon fiber, using glycerin and its derivatives as plasticizers.

State of the art [002] It is known that polyacrylonitrile (PAN) homo or copolymerized, when heated above 180 ° C, the nitrogen of the nitrile group undergoes cyclization and, consequently, causes the formation of cross-links in the polymeric chain, producing a rigid structure, as shown in Formula 1. Cyclization is a strongly exothermic reaction and when the temperature exceeds 300 ° C, polymer mass loss due to the release of gases such as water, carbon oxides, ammonia and hydrocyanic acid, resulting in a dark, fragile and porous by-product, with total loss of the physical and mechanical properties of the original polymer.

Formula 1 - PAN cycling

Ç

/ Π> 1SO ° C

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Η Η Η η Η Η «\ / Η V Η \ / ¥« II | / c ^J f ¹ C f ¹ Γ ¹ sss /

NNNN / n [003] This characteristic of PAN, makes the production processes of precursor fiber of carbon fiber to be carried out at low temperature, by traditional processes that are practically the same as when they were developed for textile fibers by Dupont in the decade 1950. Industrially only two spinning processes are used, both of which use solvents and we can quote:

- Wet spinning process, is carried out by dissolving the polyacrylonitrile in a highly polar solvent to produce a collodion with a typical concentration of 10% to 30% of polymer. This viscous collodion is pumped into circular dies with thousands of holes of approximately 50 microns, immersed in a bath containing an aqueous solution of the same solvent and as the fibers are formed by coagulation, they are slowly stretched, washed and dried. This spinning process is responsible for most of the production of PAN fibers in the world, with the main variation between the producing industries being the types of solvents used, and among the most common are, dimethylformamide (DMF), dimethylacetamide ( DMAc), dimethylsulfoxide (DMSO) and sodium thiocyanate solution (NaCNS). Less used are the zinc chloride solution (ZnCl ₂ ), nitric acid and ethylene carbonate (EC). For the production of precursor carbon fiber fiber, mainly

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3/32 sodium thiocyanate solution and zinc chloride solution, which allow the polymerization of the acrylonitrile monomer (AN), directly in the solution to a suitable viscosity for spinning. This process is known as solution polymerization ”. In textile industries that use organic solvents such as DMF and DMAc for the production of PAN fibers, the polymer is produced by the suspension polymerization process ”, after being formed, filtered, dried and stored in silos. Collodion is produced with this dry polymer just before spinning, which allows the process to work independently of the polymerization and with great production capacity.

- Dry spinning process, much less used than wet spinning, was initially developed by Bayer in Germany in the 1950s, and makes use of collodes containing organic solvents such as DMF, which is heated and pumped into the spinners inside a hot air chamber. In these conditions, the collodion when leaving the die has the solvent quickly evaporated, with the formation of the filaments. The other stages of drawing and finishing the fibers are similar to the wet spinning process. DMAc can be used in this process, but it produces more viscous collodes and its ignition temperature is 100 ^o C lower than DMF and therefore less safe.

[004] For reasons of production costs, environmental and occupational factors, over the last 30 years, numerous researches have been carried out regarding PAN spinning methods without the use of solvents, based on their melting spinning. The technological challenge is very big for the development of spinning processes

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4/32 continuous by melting spinning, since the melting point of PAN is located at a temperature higher than the temperature of cross-linking and decomposition. For homopolymer PAN, its melting point can only be observed by differential scanning calorimetry (DSC) technique with very high heating rates and is located at approximately 340 ^o C, which is very high and does not allow the residence time polymer melted in the extruder to perform the spinning. Even with the addition of comonomers that lower the melting temperature of PAN, the temperature remains above 300 ^o C. To circumvent this chemical characteristic of the polymer that prevents its direct spinning by the melting process, as is done with Nylon and polypropylene (PP), some methods have been studied and patented, but until today without commercial fiber production.

[005] Basically the PAN fusion methods that can be used for the production of fibers can be divided into two categories, with some having reported the production of carbon fibers and others not: 1) methods that use plasticizers for the PAN; 2) methods using intrinsically thermoplastic PAN copolymers.

[006] The following will discuss these methods, their advantages and limitations for the production of carbon fiber:

1. Methods that use plasticizers for PAN.

[007] For the production of PAN fibers by these methods, plasticizing substances are added to the copolymers that delay or prevent their decomposition at the extrusion temperature, similarly to what is already done with polyvinyl chloride (PVC) in industry. For obvious reasons, for the production of carbon fibers with fibers containing

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5/32 plasticizers, these interfere in the process of stabilization and oxidation of the fibers because they are not incorporated into the polymeric chain of PAN and tend to be volatilized during heating, leading to the rupture of the filaments. PAN plasticization processes are described below as a), b) and c):

a) Based on the use of water as a plasticizer. This process was initially developed by BASF in Germany in the 1980s by Daumit et al. and described in EP 0355762 A2 of 1989 and US 5168004 of 1992. Basically the inventors describe an equipment that allows the fusion of PAN in a medium containing mainly water and acetonitrile, in a range of 140 ^o C to 190 ^o C with pressure of 3.8 bar, to keep the solution in a liquid state and thereby hydrate and plasticize the polymer. For operational reasons, despite the use of water as a plasticizer, which is abundant, inexpensive and non-toxic, high pressure plasticization and spinning is very difficult to do and until today this process has never become commercial, whether for textile and carbon fiber production, since the inventors mentioned having produced carbon fibers with a toughness> 2000 Mpa. The patents of Yoon et al. US 5434002 and US 5,589264 describe the production of PAN fibers from the hydrate extrusion and also with a mixture of water and acetonitrile. In this case, the fibers obtained were not continuous and their diameters and lengths were very irregular and therefore cannot be used in the production of carbon fiber.

b) Based on the use of PAN solvents as plasticizers. Solvent like DMSO, DMF, carbonate

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6/32 ethylene (EC) and ionic liquids are described in the literature with good PAN plasticizers. Merz et al. describes in US patents 5304590 and US 5589520 the use of ethylene carbonate for the production of films and foams and suggests the possibility of the resin containing PAN / EC being used in the production of fibers, but does not report how they would be obtained or applied in the production of carbon fiber. The proportion of plasticizer used in these patents was 30% to 60% and the extrusion and drawing process was carried out in a temperature range of 79 ^o C to 204 ^o C to obtain the films and foams. A major advantage of this process is the use of low toxicity substances, such as EC, and the possibility of producing PAN films that cannot be obtained continuously in wet processes. But due to the high content of plasticizer used and its high boiling point which is 261 ^o C, it is not possible to perform thermal stabilization of the fibers, which takes place between 180 ^o C and 200 ^o C. Even if it were possible to stabilize these fibers at a higher temperature, the large amount of plasticizer present that would volatize would cause many defects, both on the surface and inside the fiber, leading to the rupture of the filaments. As a consequence, these carbon fibers would be of poor quality, low carbon yield and high cost, since EC is a more expensive raw material than the solvents used in wet spinning processes. US patent 8906278 B2 from Yu et Al. Published in 2014, describes the use of ionic liquids derived from imidazole as plasticizers for the production of fibers, using extruders in a temperature range of 170 ^o C to 220 ^o C. These fibers presented toughness> 2 cN / tex e

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7/32 were able to be stabilized, oxidized and generate carbon fiber with tenacity greater than 3 GPa, according to the authors. Unfortunately, these ionic liquids used are not produced on an industrial scale and have prohibitive prices when compared to conventional PAN solvents, bringing no economic advantage to the process, even though the production costs of fibers by melting spinning process are lower.

c) Based on the use of PAN blends with thermoplastic polymers. Various low melting point polymers are used in this process, which can form blends with PAN copolymers, such as polyethylene glycol, polycarbonate, polycaprolactone and polyphenylene oxide. US patent 7541400 B2 2009 to Lutzmann et al. describes the production of PAN thermoplastic blends, mainly containing polycarbonate and polyphenylene oxide, stabilized with metallic salts of calcium, strontium, magnesium, manganese, aluminum and boron compounds, for the production of films with good transparency and gas barrier. Blend films were produced by pressing at temperatures of 200 ^o C to 227 ^o C. The advantage of this method is the production of PAN products that cannot be produced by wet processes, such as transparent films, but due to the addition of non-toxic compounds. carbon together with PAN, could hardly generate carbon fibers with satisfactory mechanical properties. It is also known that the presence of metals in PAN fibers, can generate alkaline cyanides at high temperature and when they volatize they can vitrify and seriously damage refractories in carbonization furnaces. For this reason, the specifications of

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8/32 non-carbon compounds, such as alkali metals, in precursor fibers, are very strict.

2. Methods that use intrinsically thermoplastic PAN copolymers.

[008] US patents 5602222 and 5618901, describe the obtaining of meltable acrylic polymers from copolymerization of acrylonitrile with various comonomers such as methacrylonitrile, methyl methacrylate and methyl acrylate, polymerized by "emulsion process" in the presence of emulsifiers, in the presence of emulsifiers. -mercaptanes and ammonium persulfate as initiator. The polymers obtained under the described polymerization conditions have physical and mechanical properties suitable for extrusion and can be found commercially under the Barex brand, currently marketed by the company INEOS. Because they are not sold pure and have several additives in the formulation as extrusion aids, mineral fillers and pigments, the correct name for Barex resins. According to the manufacturer, these resins are suitable for film extrusion, blow molding and have oxygen barrier properties better than polyethylene terephthalate (PET) used in bottles and packaging. These resins do not have rheological spinning properties and therefore the manufacturer does not recommend application for melting spinning. The production of carbon fiber with Barex resins is very unlikely, as they are expensive, have a low content of acrylonitrile monomer and are thermoplastic, when heated for stabilization, the fibers melt and bond the filaments. Another intrinsically thermoplastic PAN copolymer that can be processed in an extruder for fiber production is that obtained by

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9/32 copolymerization with the monomer 1-vinylimidazole (VIM). In the book Poly (acrylonitrile-co-1-Vynilimidazole): a New Carbon Fiber Precursor ”by Wenjin Deng and Dennis W. Smith, published by Lambert Academic Publishing in 2012, the production of fibers with PAN-co-PVIM is described in proportion molar percent of 82/18, spun at 192 ^o C. These fibers were thermally stabilized at 250 ^o C for 5 hours and carbonized at 1000 ^o C for two hours. Despite the great result obtained with this PAN-co-PVIM copolymer for the production of fibers by melting spinning, there are two main factors in its commercial use as a precursor to carbon fiber: the price of the comonomer which is quite expensive and therefore does not bring no economic advantage for the spinning process; long time for thermal stabilization of the fibers.

Deficient points of the state of the art

1. Wet and dry spinning processes [009] Due to economic and environmental issues, in traditional wet spinning and dry spinning processes, whether for the production of textile fibers and carbon precursors, it is necessary to recovery and recycling of all the solvents used, which are highly polluting water and soil. For example, in spinning using DMF or DMAc, for each ton of fiber produced, approximately 3 tons of solvents are used. The recovery of solvents is done with great energy consumption in distillation and vacuum concentration units, but even so the water resulting from these processes contains small concentrations of solvents and needs to be treated later in chemical or biological treatment plants, to be discarded in rivers or

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10/32 reused. In the case of recovery of DMF and DMAc there is a loss of up to 5% per distillation cycle due to the formation of the respective acids (formic and acetic acid) and methylamine, which cannot be converted back into the original solvents. These losses can only be offset by purchasing more new solvents. In addition, wet and dry spinning processes result in a risk of occupational safety for operators, due to the inhalation of solvent vapors that have high toxicity. DMF, which is the most widely used solvent today, is considered hepatotoxic and can cause decreased fertility in humans. ACGIH and OSHA (USA) recommend an exposure limit (TLV-TWA) of 10 ppm for this substance. Environmental and occupational risk factors are one of the biggest obstacles to the implantation of new plants in developed countries, with most of the production of PAN fibers currently located in Asia, in countries such as China, Turkey and India, where legislation are less strict. In developed countries like the USA, virtually all factories have already closed.

A - Fusion spinning processes.

[010] For PAN spinning to be carried out continuously by melting spinning, it is necessary to use plasticizers or to produce intrinsically thermoplastic PAN copolymers. In both cases, in order to be advantageous in relation to traditional spinning processes that use solvents, both plasticizers and meltable copolymers must, in the end, produce fibers that can be stabilized and carbonized, at lower costs. Currently, for the precursor fibers of

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PAN, the cost of the precursor represents approximately 50% to 60% of the final cost of carbon fiber. Therefore, fusion spinning processes that incorporate raw materials (solvents and comonomers) are more expensive than those used in traditional spinning. In addition, the fibers obtained by this process must be processed in conventional carbon fiber production equipment with good productivity to reduce operating costs, especially energy consumption, and the use of precursor fibers obtained by fusion, which are not can be thermally stabilized in a reasonable time of 1 or 2 hours. For textile applications, the presence of plasticizers in the fibers is not relevant, as long as they do not significantly affect their properties. In the case of the production of carbon fibers, plasticizers make the stabilization time very long, if not impractical, in addition to causing structural defects in the fibers by volatilization, leading to the loss of their mechanical properties. The volatilization of plasticizers in the stabilization process also has an impact on costs, whether due to the loss of raw materials and the volume of cyanide / ammonia liquid and gaseous effluents that must be treated.

[011] It was mainly thinking about the production of low-cost carbon fiber that led to the realization of the present invention, considering: aspects of simplification that the fusion spinning process entails when compared to those of wet / dry spinning; use of cheap and low toxicity raw materials; use of raw materials from renewable resources that cause low environmental impact;

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12/32 that the obtained fibers can be stabilized / oxidized in a similar way to the precursor fibers produced in conventional processes.

Summary of the invention [012] The technical problems mentioned above were solved in this present invention, allowing the production of precursor carbon fiber starting from PAN, spun by melting spinning in conventional equipment, using derived raw materials as plasticizers of the biodiesel production chain, such as glycerin or glycerol. The transesterification of vegetable oils leads to the production of 10% glycerin, which currently makes it a raw material of potential industrial use due to its low cost, high production and atoxicity and for being part of all triglycerides that exist in living beings. The fibers obtained by the present invention have characteristics similar to those produced by wet spinning processes and therefore can be processed in conventional carbon fiber furnaces.

[013] As described in the literature, such as in the book “Acrylic Fiber Technology and Applications edited by James C. Masson in 1995 and in US patent 3388202 of 1968 by Opferkuch and Ross et al., One of the first to address the issue of PAN, it is known that this polymer when mixed with substances of high dipolar moment, such as water, can be melted under high pressure at temperatures below 200 ^o C in the form of a hydrate and formed thermoplastic into fibers. Under these conditions, the intramolecular interaction of the dipoles of the neighboring CN cluster is weakened and the polymer melts, without cyclization occurring.

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13/32 of the chain. By using substances with a high dipole moment and high boiling point, mainly consisting of glycerin and glyceryl carbonate (GC), employing thermal stabilizers such as glycerin-derived halohydrins, such as 1-chlorine 2,3-propanediol, 1,3dichloro 2 -propanol, 1-bromo 2,3-propanediol, phosphoglyceric acids such as 2-phosphoglyceric and 3-phosphoglyceric acid, and the chlorinated polymers of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC), the inventor found that the effect of melting fusion PAN is similar to that observed by using high pressure water. In these conditions, the PAN can be kept fused for a reasonable time in order to allow its thermoplastic conformation in an extruder.

[014] Glycerin and its derivatives after melting and cooling PAN, are incorporated into the polymer, similarly to what occurs with PVC, which also becomes thermoplastic after the addition of plasticizers, such as esters of phthalic acid. The entire plasticization and melting process of PAN takes place directly in the extruder, allowing the molten material to be transported and pumped using gear pumps to a die containing dozens or hundreds of holes in the order of 100 to 500 pm in diameter, forming the multifilaments that are stretched. The great advantage of using glycerin and its derivatives in this present invention as plasticizers, is that they are completely soluble in water and therefore easily removed from the fibers, in a step called in this patent, which is carried out immediately after spinning.

[015] After de-plasticizing the fibers are dried,

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14/32 stretched in rolls with a temperature of 150 ^o C to 170 ^o C, covered and coiled.

[016] The amounts of glycerin and glycerin carbonate that can be absorbed by PAN copolymers during melting are not constant and vary according to the comonomer content and molecular weight, with quantities that exceed the maximum absorption capacity being segregated during extrusion and can be eliminated by the extruder degassing hole. For this reason, the amount of plasticizers and their combinations used in this invention is a maximum of 35% and the polymers used can contain up to 30% comonomers, mainly vinyl acetate, methyl acrylate, methyl methacrylate, itaconic acid, acrylamide, acrylic acid, vinylidene chloride, styrene and vinyltoluene.

[017] The precursor fibers thus obtained because they are de-plasticized, can be stabilized and oxidized at temperatures between 180 ^o C and 280 ^o C and carbonized between 1000 ^o C and 1500 ^o C. The plasticizers that leave the fiber and stay in the bath have low toxicity and high rate of biodegradation as they consist basically of glycerin mixed with its derivatives and can be discarded in a biological treatment plant.

[018] Since glycerin is an abundant raw material on the market due to being a residue of 10% of the amount of vegetable oils used in the production of biodiesel, its current price in Brazil in 2014 was US $ 200 / Ton with a production estimated at 300,000 Ton / Year and consumption in the order of 40,000 Ton / Year, with a surplus of 260,000 Ton / Year in the country. World production of

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15/32 glycerin is increasing, being estimated in 2015 as> 2 million tons. These data show that, due to the low price and large supply, the energy cost necessary to recover glycerin from the deplastification bath is not economically viable and, therefore, the best alternative is its disposal as an auxiliary nutrient in a biological treatment plant. sanitary or domestic sewage, since it is completely metabolized by microorganisms that use it as an energy source. In laboratory tests with baths rich in glycerin with chemical oxygen demand (COD) of 50000 mg / L and 10x dilution factor with sanitary sewage with a COD concentration of 20000 mg / L, it was demonstrated that in 12 hours of treatment , the glycerin content was reduced by 93% and with 24 hours by 96%. Other glycerin derivatives in the halohydrin form when present and used in low concentrations, such as, for example, 1-chlorine 2,3-propanediol, are easily hydrolyzed to pH 9 to produce glycerin and release chloride ion. Likewise, glycerin carbonate and glycerin fatty monoesters undergo hydrolysis releasing glycerin. When phosphoglyceric acids are used as additives, the phosphoric acid produced in hydrolysis is also an important nutrient. Another alternative to the disposal of baths containing glycerin is its use as a raw material for the synthesis of several useful substances, among which we can mention the biopolymer gamma-polyglutamic acid (γPGA), formed by fermentation with “Bacillus natto”, the same one that produces the typical Japanese fermented soybean food known as Natto. Several patents describe the synthesis of γ-PGA in media containing mainly glycerin in

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16/32 concentrations up to 80g / L, including US patent 6989251 by Lee et al. of 2006. γ-PGA, like glycerin, is non-toxic and in aqueous solution is highly viscous, having the ability to flocculate most of the heavy metals present in water. For this reason, its use in water treatment to replace polyacrylates, polyacrylamides and aluminum salts is increasing.

[019] The characterization of the present patent application for Privilege of Invention now proposed is made by means of representative figures of the POLYACRYLONITRILLA COMPOSITION AND USE OF THE SAME ”, in such a way, that the method can be fully reproduced by appropriate technique.

[020] Based on the figures elaborated, the descriptive part of the report is based, through a detailed and consecutive numbering, which clarifies aspects that may be implied by the adopted representation, in order to clearly determine the protection sought.

[021] These figures are merely illustrative and may vary.

Brief description of the drawings of the invention [022] Below, for a better understanding and understanding of how the POLYACRYLONITRILLA COMPOSITION AND USE OF THE SAME is constituted ”, which is claimed here, the following illustrative figures are presented, where it can be seen:

[023] FIG. 1 shows the flowchart of the production process for PAN fibers produced by melting spinning in an extruder, according to this patent application.

[024] FIG. 2 shows the cross section of 4.5% PAN-co-PVA fibers with 27.5% plasticizers.

[025] FIG. 3 shows the DSC of a sample of a

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17/32 PAN-co-PVA copolymer 6.0% plasticized with 15% glycerin 10% glycerin carbonate, showing the visualization of the melting endothermic peak at 223 ^o C, just before the exothermic peak related to the cyclization of the polymeric chain at 382 ^o C, a fact that was not observed in the copolymer without being plasticized.

[026] FIG. 4 shows, by Infrared Spectroscopy (FTIR), the spectral comparison of 6% plasticized PAN-co-PVA fiber samples with 15% glycerin and 10% glycerin carbonate, before and after washing with water at 80 ^o C. The efficiency of the deplastification process is evidenced by the absence of the 3400 cm ^-1 band in the washed fiber, referring to the OH group present in the glycerin used as a plasticizer.

[027] FIG. 5 shows the thermal stabilization of the 10% PAN-co-PS deplastified fiber at 190 ^o C for 50 minutes.

[028] FIG. 6 shows, at the top, the longitudinal sections of the precursor fiber of PAN-co-PVA 6% and at the bottom, longitudinal sections of carbon fiber obtained by carbonization at 1000 ^o C of de-plasticized precursor and stabilized at 190 ^o C for 50 min . and oxidized at 275 ^o C for 15 min.

Detailed description of the invention [029] The present invention is the production of Thermoplastic Polyacrylonitrile fiber intended for the manufacture of carbon fiber, comprising the following steps: (I) preparing a PAN copolymer composition, glycerin-derived plasticizers, stabilizers and additives in the powder or pellet form; (II) transfer to an extruder; (III) subjecting step (I) to an extrusion process; (IV) obtaining

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18/32 of the PAN fibers; (V) to deplast the fibers in hot baths; (VI) carrying out the drying of the fibers, (VII) carrying out the hot drawing of the PAN fibers; VIII) application of ensimaging oil; IX) obtaining coils of fibers.

[030] According to Figure 1, which shows the flow chart of the PAN melting spinning process of this invention, the copolymer mixed with plasticizers in the form of powder or pellets are fed into the funnel of the extruder. The extruder operates in a temperature range of 150 ^o C to 250 ^o C and fuses the PAN and transports it to a gear pump that has the function of producing a high pressure of pumping viscous fluid through the die. In this present invention circular dies of 50 to 200 holes were used, with diameters of 200 to 500 microns. Right after the spinneret leaves, the filaments that are already cooled are taken to several hot baths containing solvents capable of dissolving the plasticizers used and that do not attack the fibers. In the case of the use of glycerin and glycerin carbonate as plasticizers, water, ethanol, methanol, propanol, isopropanol and their aqueous solutions can be used.

[031] With the use of water as a plasticizing solvent, the working temperatures are between 70 ^o C and 93 ^o C, being carried out in 3 stages to minimize the dragging of solubilized plasticizers from one vat to another. Cuba 1 works at a temperature of 70 ^o C with a bath renewal rate of 15% / hour. The temperature in Cuba 2 is 80 ^o C and the rate of renewal is 5% / hour. For the complete removal of plasticizers from the fibers, the maximum

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19/32 possible temperature of the water bath, which can be from 90 ^o C to 95 ^o C in Cuba 3, depending on the local atmospheric pressure. In this third tank the rate of replacement of the bath by evaporation and renewal is 5% / hour.

[032] Using a 25% to 50% ethanol solution as a de-plasticizing liquid, temperatures should be reduced by 10 ^o C, and the temperature in the third bath should not exceed 80 ^o C. Fibers de-plasticized with an ethanol bath / water are easier to dry and lose their initial yellow color. Methanol can also be used, but additional precautions must be used, since its vapors are very toxic.

[033] Each tub in the deplastification bath of this present invention was 15 cm high, 20 cm wide and 150 cm long, with a useful capacity of 40 L. The heating was carried out with electrical resistance of 6000 W, allowing temperature adjustment with variation of + / 3 ^o C. The renovation of the baths was carried out using Masterflex peristaltic pumps.

[034] Right after leaving the bath, the fibers are taken to a quintet of rolls heated between 140 ^o C to 160 ^o C and a typical speed of 50 m / min for drying and then to another quintet of rolls heated to the same temperature with a typical speed of 200 m / min, where drawing is carried out. Lubricated and anti-static oil (ensimaging) is applied to the fibers already stretched, which is important for the production of coils with more uniform cables and with little breakage of filaments.

[035] PAN fibers produced in accordance with this invention have a moisture content <1% and an ensimage of 0.1%

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20/32 to 0.5%. The filaments have circular cross sections, have no voids or holes and the diameters can vary according to the drawing rate of 10 to 50 microns, as can be seen in Figure 2.

[036] In the process described, the inventor solved the problem of PAN spinning by melting spinning, performing its plasticization with glycols, more specifically with the use of glycerin and its derivatives. According to Figure 3, it can be clearly seen in the DSC of the plasticized PAN copolymer, its melting zone at a temperature much lower than that of the exothermic cyclization of the chain, which allows the use of extruders for fiber production. The plasticization of PAN with high dipole moment substances such as water and glycols, makes the nitrile nitrogen dipole preferentially attracted by the dipoles of the hydrogens of these substances, delaying the formation of cross-links with neighboring carbons in the chain, allowing their fusion.

[037] Even with the heating of the plasticized PAN with glycerin, glycerin carbonate and their mixtures, its cyclization starts between 5 to 10 minutes after melting, observed by the color change of the molten polymer that becomes a light yellow and fluid if dark brown and slimy. This residence time in the molten form is too short for processing in an extruder. It has been found that if some halogenated or phosphorous additives are added in small concentrations along with PAN plasticizers, the polymer can remain melted for up to 1 hour, long enough to allow for continuous processing. These additives are referred to in this invention as

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21/32 cyclization stabilizers and can be: high boiling inorganic acids such as phosphoric acid in the form of their esters with glycerin, such as phosphoglyceric acids, most commonly 2-phosphoglyceric and 3-phosphoglyceric acid; halohydrins derived from glycerin, such as 1-chlorine 2,3propanediol, 1,3-dichloro 2-propanol, 1-bromo 2,3propanediol, 1,3-dibromo 2-propanol; and the chlorinated polymers polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC).

[038] Other additives in this invention such as glycerin-derived mono and fatty acid esters, more specifically glyceryl monostearate, glyceryl distearate, glyceryl monooleate, glyceryl dioleate, glyceryl monolaurate, glyceryl monopalmitate, glyceryl dipalmitate , glyceryl monomyristate and their mixtures, are called lubricants and the substances ethylene carbonate, propylene carbonate, ethylene glycol, diethylene glycol, triethylene glycol and their mixtures are called viscosity reducers.

[039] The proportions of plasticizers and additives used in the present invention are at most 35% and cyclization stabilizers at most 5%.

[040] At the same time, by selecting substances that are soluble in polar solvents such as water and alcohols, the inventor solved the problem of eliminating the plasticizers from the fibers, which are unwanted in the thermal stabilization stage, introducing deplastification baths. The use of non-soluble plasticizers in the baths would result in the use of other types of organic solvents to eliminate them from the fibers, which would be

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22/32 a great economic and environmental disadvantage for the melting spinning spinning process proposed in this invention. As a result, the fibers leaving the deplastification baths are similar to those produced by wet spinning processes and can be stabilized, oxidized and carbonized in traditional carbon fiber production furnaces.

[041] Figure 4, shows by infrared analysis (FTIR), that the same plasticizers that cause PAN fusion, are easily removed from the fibers by washing with hot water, which in this invention was called the deplastification step. The fibers coming out of the deplastification baths are similar to those produced by the wet process as they are essentially made up of PAN copolymers and therefore the stabilization, oxidation and carbonization stages are also similar to those used for traditional precursor fibers.

[042] Figure 5 shows that the PAN fibers deplastified when kept isothermally at 190 ^o C, are stabilized in a time interval equivalent to the fibers produced by the wet process, including the same color gradient, initially white, yellowish, golden, brown and finally black.

[043] After thermal stabilization of these fibers, the oxidation and carbonization processes are carried out as for any PAN precursor, producing carbon fibers with a C> 90% content, tenacity> 1 GPa and excellent mechanical properties for different applications, as is shown in Figure 6.

[044] The copolymers of the present invention have more than 70% units derived from acrylonitrile,

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23/32 copolymerized with one or more comonomers, and represented by acrylic units, such as:

(—CH2-CH ...)

CN [045] The glycerin mentioned in this invention was purified from biodiesel glycerin by chemical treatment and removal of water and methanol by vacuum heating, without distillation. Due to the low glycerin content, the presence of unconverted fatty acids, lecithins, sodium hydroxide, sodium salts, and residual methanol, it is not possible to use it as a PAN plasticizer without its purification. For this, a sample of residual glycerin provided by the company Bioverde located in the city of Taubaté (Brazil) with a content of 85% was submitted to the following process, based on the literature and described in Rev. Virtual Quim., 2014, 6 (6), pgs . 1564-1582: For 5.0 kg of crude glycerin heated to 70 ^o C, 100 ml of 85% phosphoric acid was added under agitation. Under these conditions and after decanting, the fatty acids and lecithins are separated from the glycerin. This glycerin was filtered on an activated carbon bed for color removal and then passed on an ion exchange resin cartridge containing Amberlite IR 120 cationic resin to remove sodium salts. This glycerin was heated to 90 ^o C under vacuum for 1 hour to remove water and residual methanol. The final product had a 98% purity content, 0.047% ash and sodium <20 mg / kg (ppm) and can be used as a PAN plasticizer in this invention. The other raw materials used here, such as: Glycerin carbonate was purchased from Huntsman and marketed under the brand Jeffsol Glycerine

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24/32

Carbonate; PVC was acquired from Braskem and marketed under the Norvic brand; the glycerin fatty esters were purchased from Polytechno Indústrias Químicas; ethylene glycol and diethylene glycol were purchased from Oxiteno; the acrylonitrile, vinyl acetate, itaconic acid and acrylamide monomers were provided by the company Radifibras; all other raw materials were purchased from Sigma-Aldrich do Brasil.

[046] To better demonstrate the preferred embodiments, which are representative, but not limiting to the experiments carried out, we present below examples of application of the present invention; the acrylic copolymers described in that patent were produced by suspension polymerization employing acrylonitrile, comonomers, potassium persulfate (initiator, oxidizing agent), sodium bisulfite (activator, reducing agent), ammoniacal ferrous sulfate (redox catalyst) and tetrasodium EDTA (chelating agent ), according to the methodology described in the literature, “Acrilic Fiber Technology and Applications, James C. Mason, 1995, pgs. 37 to 67.

[047] Example 01: approximately 2000g (72.1%) of PAN copolymerized with 4.5% vinyl acetate with Mw 146,000, moisture content of 0.65% and granulometry <20 pm, was mixed in a blender at 90 ^o C under stirring with 570g (20.6%) of glycerin, 40.5g (1.5%) of 3-chloro-1,2-propanediol, 93.4 g (3.4%) of glyceryl monostearate , 52.5 (1.9%) g of 85% phosphoric acid and 15.9g (0.6%) of ethylene glycol. After 20 minutes of homogenization, the mixture was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 pm was separated and fed in a

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25/32 screw extruder 20mm and extruded at a speed of 75 rpm, with 5 heating zones, the first zone with 248 ^o C, the second, third and fourth zone with 220 ^o C and the fifth zone comprising the pump gear and the die at 230 ^o C. In this example, the die presented 90 holes with a diameter of 250 pm. The fiber cable was de-plasticized with hot water in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 55 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with a speed of 180 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) applied and then wound. The fibers obtained in this example showed a yellowish color, diameter of 28 pm, resistance of 19 cN / tex, humidity of 0.8% and ensimagem content of 0.24%.

[048] A 90-filament fiber cable was stabilized at 185 ^o C for 55 minutes and heated at a speed of 10 ^o C / min to 280 ^o C. The temperature was maintained for 20 minutes. The oxidized black fiber was carbonized at 1000 ^o C in nitrogen atmosphere for 12 minutes. The yield was 62.5% carbon, with a diameter of 17pm, tenacity of 1.75

GPa and 128 GPa module.

[049] Example 02: approximately 2000g (69.3%) of PAN copolymerized with 4.0% vinyl acetate, 2.5% itaconic acid with 137,000 Mw, moisture content of 0.80% and particle size <20 pm, was mixed in a blender at 90 ^o C with stirring with 480g (16.6%) glycerin, 200 g (6.9%) glycerin carbonate, 35.5g (1.2%) 3-chlorine -1.2propanediol, 78.1 g (2.7%) of glyceryl monooleate, 64.3 (2.2%) g of 85% phosphoric acid and 28.3g (1.0%) of ethylene glycol. After 20 minutes of homogenization the mixture

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26/32 was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 μm was separated and fed into a 20mm screw extruder and extruded at a speed of 75 rpm, with 5 heating zones, the first zone being 235 ^o C, the second zone , third and fourth zone with 215 ^o C and the fifth zone comprising the gear pump and the die with 225 ^o C. In this example, the die presented 50 holes with a diameter of 500 μm. The fiber cable was de-plasticized with hot water in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 40 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with a speed of 150 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) being applied and then wound. The fibers obtained in this example were light yellowish in color, 35 μm in diameter, 15 cN / tex resistant, 0.8% moisture and 0.30% staining content.

[050] The 50-filament fiber cable was stabilized at 185 ^o C for 80 minutes and heated at a speed of 10 ^o C / min to 260 ^o C. The temperature was maintained for 20 minutes. The oxidized black fiber was carbonized at 1000 ^o C in nitrogen atmosphere for 12 minutes. The yield was 61.0% carbon, with a diameter of 24 μm, tenacity of 1.52

GPa and 97 GPa module.

[051] Example 03: approximately 2000g (70.0%) of PAN copolymerized with 10.1% styrene with Mw 158,000, moisture content of 0.50% and granulometry <20 μm, was mixed in a blender at 90 ^o C under stirring with 480g (16.8%) of glycerin, 150 g (5.2%) of glycerin carbonate, 75.5 g (2.6%) of 3bromo-1,2-propanediol, 35.5g ( 1.2%) PVC NORVIC SP 700 HF

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27/32 (Braskem), 79.4 g (2.8%) of 85% phosphoric acid and 38.7 g (1.4%) of diethylene glycol.

[052] After 20 minutes of homogenization, the mixture was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 pm was separated and fed into a 20mm screw extruder and extruded at a speed of 55 rpm, with 4 heating zones, the first zone being 230 ^o C, the second and third with 220 ^o C and the fourth zone with 225 ^o C comprising a 3 mm diameter bore head. The extrudate was stretched to 1.5 mm in diameter and cut into pellets of 2 mm in length.

[053] These pellets were fed into a 20mm screw extruder and extruded at a speed of 75 rpm, with 5 heating zones, with the first zone at 235 ^o C, the second, third and fourth zone at 225 ^o C and the fifth zone comprising the gear pump and the 230 ^o C. die. In this example, the die presented 120 holes with a diameter of 250pm. The fiber cable was de-plasticized with hot water in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 55 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with a speed of 190 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) being applied and then wound. The fibers obtained in this example were orange, 22 pm in diameter, 21 cN / tex strength, 0.9% moisture content and 0.25% ensimage content.

[054] The 120-filament fiber cable was stabilized at 190 ^o C for 50 minutes and heated at a speed of 10 ^o C / min to 280 ^o C. The temperature was maintained for 10 minutes. The black oxidized fiber was carbonized at 1000 ^o C in

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28/32 nitrogen atmosphere for 12 minutes. The yield was 60.5% carbon, with a diameter of 17 μm, tenacity of 1.78 GPa and a module of 112 GPa.

[055] Example 04: approximately 2000 g (71.5%) of PAN copolymerized with 2.4% acrylamide and 2.5% methyl acrylate with Mw 163,000, moisture content of 0.70% and particle size <20 μm, it was mixed in a blender at 90 ^o C under agitation with 310g (11.1%) of glycerin, 300 g (10.7%) of glycerin carbonate, 40.0g (1.4%) of a mixture of 60 % glyceryl monostearate and 40% glyceryl distearate, 35.5g (1.3%) of NORVIC SP 700 HF PVC, 55.8g (2.0%) g of mixture containing 2-phosphoglyceric acids and 3-phosphoglyceric acid with 25% phosphoric acid and 57.1g (2.0%) of propylene carbonate.

[056] After 20 minutes of homogenization, the mixture was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 μm was separated and fed in a 20mm screw extruder and extruded at a speed of 50 rpm, with 4 heating zones, the first zone being 245 ^o C, the second and third with 228 ^o C and the fourth zone with 228 ^o C comprising a 3 mm diameter bore head. The extrudate was stretched to 2.0 mm in diameter and cut into pellets of 2 mm in length.

[057] These pellets were fed into a 20mm screw extruder and extruded at a speed of 80 rpm, with 5 heating zones, with the first zone with 238 ^o C, the second, third and fourth zone with 229 ^o C and the fifth zone comprising the gear pump and the die with 229 ^o C. In this example, the die presented 50 holes with a diameter of 500 μm. The fiber cable was de-plasticized with hot water

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29/32 in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 50 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with a speed of 200 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) being applied and then wound. The fibers obtained in this example were orange in color, 40 pm in diameter, 14 cN / tex strength, 0.6% moisture and 0.35% sizing content.

[058] The 50-filament fiber cable was stabilized at 180 ^o C for 50 minutes and heated at a speed of 10 ^o C / min to 275 ^o C. The temperature was maintained for 20 minutes. The oxidized black fiber was carbonized at 1000 ^o C in nitrogen atmosphere for 12 minutes. The yield was 59.75% carbon, with a diameter of 26 pm, tenacity of 1.33

GPa and 78 GPa module.

[059] Example 05: approximately 2000 g (65.5%) of PAN copolymerized with 4.6% methyl acrylate and 6.0% styrene with Mw 121,000, moisture content of 0.50% and particle size <20 pm, was mixed in a blender at 90 ^o C with stirring with 555g (18.2%) of glycerin, 280 g (9.2%) of glycerin carbonate, 22.5g (0.7%) of 1.3 -dichloro 2propanol, 72.5 g (2.4%) of a 60% mixture of glyceryl monostearate and 40% of glyceryl distearate, 65.5 g (2.1%) of 85% phosphoric acid and 57.1 g ( 1.9%) of propylene carbonate.

[060] After 30 minutes of homogenization, the mixture was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 pm was separated and fed in a 20mm screw extruder and extruded at a speed of 60 rpm, with 4 heating zones, and

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30/32 the first zone at 235 ^o C, the second and third zone at 215 ^o C and the fourth zone at 220 ^o C comprising a 3 mm diameter bore head. The extrudate was stretched to 2.0 mm in diameter and cut into pellets of 2 mm in length.

[061] These pellets were fed into a 20mm screw extruder and extruded at a speed of 75 rpm, with 5 heating zones, with the first zone at 235 ^o C, the second, third and fourth zone at 220 ^o C and the fifth zone comprising the gear pump and the die 220 C. in this example , the die had 150 holes with diameter of 250 pm. The fiber cable was de-plasticized with hot water in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 45 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with speed 185 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) applied and then wound. The fibers obtained in this example showed a light yellow color, diameter of 20 pm, resistance of 23 cN / tex, humidity of 0.9% and ensimagem content of 0.18%.

[062] The fiber cable with 150 filaments was stabilized at 180 ^o C for 70 minutes and heated at a speed of 10 ^o C / min up to 260 ^o C. The temperature was maintained for 20 minutes. The oxidized black fiber was carbonized at 1000 ^o C in nitrogen atmosphere for 12 minutes. The yield was 60.85% carbon, with a diameter of 11 pm, tenacity of 1.68

GPa and 128 GPa module.

[063] Example 06: approximately 2000 g (70.8%) of PAN copolymerized with 6.0% vinyl acetate produced by the company Radicifibras with Mw 129,000, moisture content of 0.50% and granulometry <20 pm, was mixed in a blender

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31/32 at 90 ^o C under stirring with 520g (18.4%) glycerin, 135 g (4.8%) glycerin carbonate, 43.8 g (1.6%) 60% monostearate mixture glycerol and 40% glyceryl distearate and 63.4 g (2.2%) of 85% phosphoric acid, 25.0 g (0.9%) of polyvinylidene-co-polyacrylonitrile chloride (PVDC-co-PAN) 150,000 Mw and 38.6g (1.4%) of diethylene glycol.

[064] After 30 minutes of homogenization, the mixture was cooled for 1 hour. The obtained mass was classified in a sieve and the passing fraction less than 100 pm was separated and fed in a 20mm screw extruder and extruded at a speed of 60 rpm, with 4 heating zones, the first zone being 240 ^o C, the second and third with 222 ^o C and the fourth zone with 225 ^o C comprising a 3 mm diameter bore head. The extrudate was stretched to 2.0 mm in diameter and cut into pellets of 2 mm in length.

[065] These pellets were fed into a 20mm screw extruder and extruded at a speed of 75 rpm, with 5 heating zones, with the first zone at 240 ^o C, the second, third and fourth zone at 230 ^o C and the fifth zone comprising the gear pump and the 230 ^o C. die. In this example the die presented 150 holes with a diameter of 250 pm. The fiber cable was de-plasticized with hot water in three baths with the respective temperatures of 70 ^o C, 80 ^o C and 93 ^o C, dried at a speed of 30 m / min at 140 ^o C in a quintet of rolls and stretched at 155 ^o C with speed 125 m / min in another quintet, with an ensimaging bath (Stantex - Pulcra Chemicals) applied and then wound. The fibers obtained in this example showed a light yellow color, diameter of 35 pm, resistance of 29 cN / tex, humidity of 0.6% and ensimagem content of 0.32%.

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32/32 [066] The fiber cable with 150 filaments was stabilized at 180 ^o C for 50 minutes and heated at a speed of 10 ^o C / min to 285 ^o C. The temperature was maintained for 30 minutes. The oxidized black fiber was carbonized at 1000 ^o C in a nitrogen atmosphere for 10 minutes. The yield was 62.35% carbon, with a diameter of 26 pm, tenacity of 1.94

GPa and 187 GPa module.

[067] Due to the advantages it offers, and also because it has truly innovative characteristics that fulfill all the requirements of novelty and originality in the genre, the present “COMPOSITION OF POLYACRYLONITRILE AND USE OF THE SAME” brings together necessary and sufficient conditions to deserve the Patent of Invention Privilege.

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1/3

Claims (13)

1. Polyacrylonitrile composition characterized by containing: a) A minimum of 65% copolymer with a content equal to or greater than 70% of the acrylonitrile monomer and b) Maximum of 35% of combinations of other substances that allow the polymer to melt and spin, classified in the following groups and with the following characteristics: I) Plasticizers with a boiling point greater than 170 ^o C, soluble in water and alcohols; II) Boiling point cyclization stabilizers greater than 170 ^o C, soluble in water and alcohols or derivatives of halogenated polymers; III) Lubricants with a boiling point greater than 170 ^o C, soluble in water and alcohols; and IV) Boiling point viscosity reducers greater than 170 ^o C, soluble in water and alcohols. 2. Composition according to claim 1, characterized by containing a maximum of 30% comonomers, including vinyl acetate, methyl acrylate, methyl methacrylate, itaconic acid, acrylamide, acrylic acid, vinylidene chloride, styrene and vinyltoluene. 3. Composition, according to claim 1, characterized by containing, as plasticizers, substances with high boiling point, soluble in water and alcohols, such as glycerin, glycerin carbonate and their combinations. 4. Composition according to claim 1, characterized by containing as high stabilization substances, substances of high boiling point, soluble in water and alcohols, derivatives of glycerin such as 3-chloro-1,2Petition 870180002196, from 10/01 / 2018, p. 37/41 2/3 propanediol (α-chlorohydrin), 3-fluoro-1,2-propanediol (αfluorohydrin), 3-bromo-1,2-propanediol (α-bromohydrin), 1,3-dichloro-2-propanol, 1, 3-difluoro-2-propanol, 1,3dibromo-2-propanol and their combinations. 5. Composition according to claim 1, characterized by containing as high stabilization substances, substances of high boiling point, soluble in water and alcohols, such as inorganic acids, sulfuric acid and phosphoric acids, such as metaphosphoric acid, orthophosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphoglyceric acids and their combinations. 6. Composition according to claim 1, characterized by containing, as cyclization stabilizers, halogenated polymers and copolymers such as polyvinyl chloride (PVC), polyvinyl bromide, polyvinylidene chloride (PVDC) and polyvinylidene fluoride (PVDC) PVDF). Composition according to claims 4 to 6, characterized in that it contains a maximum of 5% cyclization stabilizers. 8. Composition according to claim 1, characterized as containing extrusion lubricants, substances with high boiling point, soluble in water and alcohols, such as gicerin-derived fatty acid mono and diesters, mainly glyceryl monostearate , glyceryl distearate, glyceryl monooleate, glyceryl dioleate, glyceryl monolaurate, glyceryl monopalmitate, glyceryl dipalmitate, glyceryl monomiristate and their combinations. 9. Composition according to claim 1, characterized in that it contains as viscosity reducers, Petition 870180002196, of 10/01/2018, p. 38/41 3/3 substances with high boiling point, soluble in water and alcohols such as ethylene carbonate, propylene carbonate, ethylene glycol, diethylene glycol, triethylene glycol and their combinations. 10. Composition according to claims 1 to 9, characterized in that in the process of deplastifying the fibers, water and alcohols from C1 to C3 such as methanol, ethanol, propanol, isopropanol or their mixtures as solvents. 11. Composition, according to claim 10, characterized by presenting a de-plasticization step that can be carried out continuously with the spinning process or discontinued directly on the obtained coils. 12. Use of the composition, as defined in claims 1 to 9, characterized in that in the preparation of polyacrylonitrile fibers spun by the melting process that can be thermally stabilized and carbonized in conventional equipment, in the same way as the fibers produced by the spinning process wet. 13. Use, according to claim 12, characterized in that it is in the preparation of polyacrylonitrile fibers spun by the fusion process that can have circular or diverse monolithic cross sections, with diameters from 5 to 500 pm and resistance> 5cN / tex. Petition 870180002196, of 10/01/2018, p. 39/41 1/4