JP2007332519A - Dispersion material containing flame-resistant polymer, flame-resistant fiber and carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion material containing a flame-resistant polymer having a forming property, especially a high forming property into a thread form. <P>SOLUTION: This dispersion material containing the flame-resistant polymer is dispersed with a salt and the flame-resistant polymer in a dispersant, wherein the flame-resistant polymer is obtained by heat-treating an acrylonitrile-based polymer, the dispersant is a polar solvent and the cationic species of the salt is ammonium ion. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a dispersion containing a flame resistant polymer, a flame resistant fiber obtained by shaping the dispersion, and a carbon fiber obtained by carbonizing the flame resistant fiber.

Flame resistant fibers are excellent in heat resistance and resistance to twisting.For example, spatter sheets that protect the human body from high-heat iron powder and welding sparks that are scattered during welding operations, etc. The demand for flame resistant fibers in these fields is increasing.

  Flame resistant fibers are also important as an intermediate raw material for obtaining carbon fibers. Carbon fiber has excellent mechanical properties, chemical properties, lightness, etc., so it can be used in various applications such as aerospace materials such as aircraft and rockets, sports equipment such as tennis rackets, golf shafts and fishing rods. It is also being used for transportation machinery applications such as ships and automobiles. In recent years, due to the high conductivity and heat dissipation of carbon fibers, there is a strong demand for application to electronic device parts such as mobile phone and personal computer casings and fuel cell electrodes.

  Carbon fiber is generally obtained by heating a high temperature flame-resistant fiber in an inert gas such as nitrogen and carbonizing it. In addition, for example, if the conventional flame resistant fiber is a polyacrylonitrile (PAN) flame resistant fiber, the PAN precursor fiber is flame resistant at a high temperature of 200 to 300 ° C. in the air (cyclization reaction of PAN + oxidation reaction). To obtain. This flameproofing reaction is an exothermic reaction and is a fiber form, ie, a solid state reaction. Therefore, it is necessary to treat for a long time for temperature control, and in order to finish the flame resistance within a desired time, it is necessary to limit the single fiber fineness of the PAN-based precursor fiber to a fineness of a specific value or less. There is. Thus, it is difficult to say that the currently known flameproofing process is a sufficiently efficient process.

  As one method for solving the above technical problem, a solution using a solvent has been studied.

For example, after heat-treating acrylonitrile-based polymer powder in an inert atmosphere until the density becomes 1.20 g / cm ³ or more, it is dissolved in a solvent to be fiberized, and the obtained fibrous material is heat-treated. A technique has been proposed (see Patent Document 1). However, since this proposal uses an acrylonitrile-based polymer powder that has not undergone a flameproofing reaction, there is a problem that the change in viscosity of the solution with time is large and yarn breakage tends to occur frequently. In addition, as a solvent, a strongly acidic solvent such as sulfuric acid or nitric acid that easily decomposes a general organic polymer is used, so it is necessary to use an apparatus made of a special material with corrosion resistance, which is also an actual cost. It was not right.

  In addition, a method has been proposed in which heat-treated acrylonitrile-based polymer powder and non-heat-treated acrylonitrile-based polymer powder are mixed and dissolved in an acidic solvent in the same manner (see Patent Document 2). Problems regarding the provision of corrosion resistance to the water and the instability of the solution remained unresolved.

  Furthermore, a method has been proposed in which polyacrylonitrile is converted into a polymer having a cyclized structure by heat-treating a dimethylformamide solution of polyacrylonitrile (see Non-Patent Document 1). It is a dilute solution with 0.5% and its viscosity is too low, so it is practically difficult to shape and shape fibers, etc., and if it is attempted to increase its concentration, the polymer will precipitate and cannot be used as a solution It was.

  Further, although a solution obtained by modifying polyacrylonitrile with a primary amine is disclosed (see Non-Patent Document 2), this solution is a polyacrylonitrile which has not been flame-resistant and has been given hydrophilicity. Thus, the technical idea is completely different from the flame resistant polymer-containing solution.

The inventors have succeeded in obtaining a dispersion containing a flame resistant polymer that can be formed into yarns and films by reacting polyacrylonitrile in a polar solvent with a nucleophile and an oxidant. Have already been proposed (Japanese Patent Application Nos. 2004-044074 and 2004-265269). As one means for further improving the productivity of the flame resistant product obtained by this method, improvement in stability in the production process of the shaped body, particularly improvement in spinning stability when forming into a yarn shape is expected.
Japanese Examined Patent Publication No. 63-14093 Japanese Examined Patent Publication No. 62-57723 “Polymer Science (USSR)” (Polym. Sci. USSR), 1968, Vol. 10, p. 1537 “Journal of Polymer Science, Part A: Polymer Chemistry” (J. Polym. Sci. Part A: Polym. Chem.), 1990, Vol. 28, p. 1623

  In view of the above problems, an object of the present invention is to provide a dispersion containing a flame resistant polymer, which is excellent in separating from a die when shaping, and to improve process stability during shaping of flame resistant fibers.

  The present invention employs the following means in order to solve such problems. That is, the dispersion containing the flame resistant polymer of the present invention is a dispersion containing a flame resistant polymer in which a salt and a flame resistant polymer are dispersed in a dispersion medium. According to a preferred embodiment of the dispersion containing the flame resistant polymer of the present invention, the concentration of the salt is in the range of 0.1 parts by weight or more and 10 parts by weight or less with respect to the total amount of the dispersion containing the flame resistant polymer. .

  According to a preferred embodiment of the dispersion containing the flame resistant polymer of the present invention, the flame resistant polymer is obtained by heat-treating an acrylonitrile-based polymer. According to a preferred embodiment of the dispersion containing the flame resistant polymer of the present invention, the dispersion medium is a polar solvent. Moreover, according to the preferable aspect of the dispersion containing the flame resistant polymer of this invention, the cation seed | species of the said salt is an ammonium ion.

  In the present invention, the dispersion containing the flame-resistant polymer can be shaped into flame-resistant fibers, and the flame-resistant fibers can be carbonized to produce carbon fibers.

  According to the present invention, when a dispersion containing a flame resistant polymer is shaped, a dispersion containing a flame resistant polymer that is remarkably well separated from the discharge port can be obtained. The dispersion containing the flame resistant polymer improves the separation of the discharge nozzle part, particularly when forming into a yarn shape, so that it is possible to suppress breakage of single yarn and adhesion at the discharge nozzle part. Become. Furthermore, as a method for shaping a dispersion containing a flame resistant polymer into a yarn shape, single yarn breakage is suppressed by either the wet spinning method or the dry-wet spinning method, and the suppression effect is particularly large in the wet spinning method. . Furthermore, since the dispersion containing the flame-resistant polymer of the present invention is easily separated from the die, the die hole density can be increased and space can be saved, so that the production efficiency is improved.

  In the present invention, it is essential that the salt is dispersed in a dispersion containing a flame resistant polymer. As a result, when the dispersion containing the flame resistant polymer is shaped, the separation of the die is remarkably improved. This appears remarkably when forming into a yarn shape, and a great improvement effect is seen in the spinnability. Although the exact reason has not been elucidated, the dispersion medium in the dispersion containing the flame resistant polymer into the coagulation bath when forming into the shape of the yarn, particularly when forming into the shape of a thread, is due to the salt being contained in the dispersion medium. It is considered that the solvent is easily removed immediately after the discharge, and the solidification property of the flame-resistant polymer, and thus the spinnability is remarkably improved.

  In the present invention, the salt is, for example, one or more dissociable hydrogen ions contained in the acid as a cation such as a metal ion or an ammonium ion, as defined in the chemical dictionary (Tokyo Kagaku Dojin 1st edition). A generic term for compounds substituted by seeds.

  Examples of the salt used in the present invention include sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, sodium carbonate, sodium hydrogen carbonate, calcium carbonate, magnesium carbonate, barium carbonate, ammonium carbonate, sodium sulfate, hydrogen sulfate. Derived from inorganic acids such as sodium, calcium sulfate, magnesium sulfate, copper sulfate, ammonium sulfate, sodium nitrate, potassium nitrate, calcium nitrate, barium nitrate, magnesium nitrate, sodium nitrate hydroxide, sodium perchlorate, aluminum phosphate and ammonium phosphate Salt, potassium formate, ammonium formate, sodium acetate, calcium acetate, ammonium acetate, ammonium propionate, sodium stearate, sodium benzoate, benzoate Ammonium acid, potassium phthalate, ammonium phthalate, ammonium isophthalate, ammonium terephthalate, potassium citrate, ammonium citrate, ammonium hydroxybenzoate, ammonium adipate, sodium methanesulfonate, ammonium methanesulfonate, ammonium benzenesulfonate And salts derived from organic acids such as ammonium tosylate and sodium tosylate. Since sodium, calcium, and other metals, even in trace amounts, remain in the fiber, the carbon fiber strength may decrease when carbonized, so that the cation species of the salt is preferably an ammonium ion. Specific examples of the salt whose cationic species is ammonium ion include ammonium benzoate, ammonium acetate, ammonium citrate, and ammonium tosylate.

  In the present invention, only one kind of salt may be used, or two or more kinds of salts may be mixed and used. Moreover, since salt should just be included when shaping the dispersion containing a flame resistant polymer, salt can be added at arbitrary time in preparation of the dispersion containing a flame resistant polymer.

  The method for adding the salt to the flame resistant polymer dispersion is not particularly restricted. A salt may be added to the dispersion medium containing the precursor polymer before heat treatment, or a salt may be added during the heat treatment, or a salt is added after a flame resistant polymer dispersion is prepared. It may be. Depending on the type of salt, a decomposition product such as an acid may be decomposed by heat treatment to inhibit the formation of the flame resistant polymer, so that a method of adding a salt to the flame resistant polymer dispersion is preferred.

  In the present invention, the salt concentration is preferably in the range of 0.1 parts by weight or more and 10 parts by weight or less based on the total amount of the dispersion containing the flame resistant polymer. When the ratio of the salt to the dispersion containing the flame resistant polymer is less than 0.1 parts by weight, the flame resistant polymer is peeled off from the die when the dispersion containing the flame resistant polymer is shaped, in particular, into a yarn shape. There is a case where the ease of change is poor and the effect of improving spinnability cannot be confirmed. On the other hand, when the concentration of the salt exceeds 10 parts by weight, the dispersion stability of the dispersion containing the flame resistant polymer may be remarkably lowered, and the clogging of the base is likely to occur. Therefore, the salt concentration is preferably in the range of 0.1 to 10 parts by weight, more preferably in the range of 0.5 to 7.5 parts by weight.

  The concentration of salt in dispersions containing flame resistant polymers can be measured by quantitative measurement methods such as ion chromatography (IC), liquid chromatography (HPLC), and gas chromatography (GC). It is.

In the present invention, a polar solvent is preferably used as the dispersion medium. The polar solvent preferably used in the present invention preferably has a relative dielectric constant of 2 or more measured by an LCR meter at room temperature, more preferably 10 or more. When the relative dielectric constant is in such a value, it is possible to disperse the flame resistant polymer more stably, and it is easy to extract the dispersion medium during the coagulation process, and it is easy to handle. If the relative dielectric constant is too small, it is difficult to extract the dispersion medium when an aqueous coagulation bath is used in the coagulation process. There is no particular upper limit for the relative dielectric constant, but if it is too large, it may be difficult to stably disperse the flame resistant polymer. Therefore, it is preferable to use a polar solvent having a relative dielectric constant of 80 or less.
Examples of the polar solvent used in the present invention include dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), sulfolane, dimethylimidazolidione, ethylene glycol, and diethylene glycol. Is mentioned. As the polar solvent, DMSO, NMP, DMF and DMAc are more preferable. Among these, DMSO and DMF are particularly preferably used because of their high solubility in salts. These polar solvents may be used alone or in combination of two or more.
In the present invention, the flame resistant polymer is a flame resistant polymer, and the dispersion containing the flame resistant polymer is a dispersion in which a component mainly composed of the flame resistant polymer is dispersed together with a salt in a dispersion medium. .

  Here, the dispersion is a viscous fluid and may be any fluid that has fluidity at the time of shaping or molding, not only fluids at room temperature, but also solids or gels that are not fluid at a certain temperature. Even if it is in the form of a material, it includes all those having fluidity near the processing temperature by heating or shearing force.

  In the dispersion containing the flame resistant polymer of the present invention, the content of the flame resistant polymer is preferably 5 parts by weight or more and 45 parts by weight or less with respect to the total amount of the dispersion containing the flame resistant polymer. When the content of the flame resistant polymer is lower than 5 parts by weight, the quality may be lowered, for example, a hole is formed in the molded product during shaping. On the other hand, when the content is higher than 45 parts by weight, the dispersion containing the flame resistant polymer is contained. This is because the fluidity of the liquid may be lowered and shaping may be difficult. The content of the flame resistant polymer is more preferably 6 parts by weight or more and 30 parts by weight or less.

  Moreover, it is preferable that the content rate of a dispersion medium is 45 to 95 weight part with respect to the whole quantity of the dispersion containing a flame resistant polymer. When the content of the dispersion medium is lower than 45 parts by weight, the dispersion stability of the dispersion containing the flame resistant polymer may be significantly reduced and the fluidity may be lost. On the other hand, when the content of the dispersion medium exceeds 95 parts by weight. This is because the viscosity of the dispersion containing the flame resistant polymer may become low and shaping may be difficult.

  In the dispersion containing the flame resistant polymer of the present invention, the viscosity near the processing temperature is 10 poise or more when measured using a B-type viscosity system at the processing temperature from the viewpoint of imparting fluidity that is easy to process. It is preferably 500 poise or less.

  In the present invention, flame resistance is substantially synonymous with the term “flameproof” and includes the meaning of the term “hard twist”. Specifically, the flame resistance is a general term indicating a property that combustion is difficult to continue, that is, a property that is difficult to burn. As a specific evaluation means for flame resistance, for example, JIS Z 2150 (1966) describes a flameproof test method (45 ° Meckel burner method) for thin materials. A sample to be evaluated (board, plate, sheet, film, thick fabric, etc. less than 5 mm thick) can be determined by heating for a specific time with a burner and evaluating the afterflame time after ignition, carbonization length, etc. . The shorter the afterflame time, the better, and the shorter the carbonization length, the better the flame resistance (flameproof) performance. In the case of textile products, JIS L 1091 (1977) describes a fiber combustion test method. After testing by this method, the flame resistance can be determined in the same manner by measuring the carbonized area and the after flame time.

  In the present invention, the shape and form of the flame-resistant polymer and flame-resistant molded article are diverse, and the flame resistance performance level is very high and has a flame resistance that does not ignite at all, to a thing that continues to a certain extent after ignition to a wide range. However, in the present invention, those whose flame resistance performance is recognized by a specific evaluation method shown in the examples described later are recognized. Specifically, it is preferable that the flame resistance performance in the flame resistance evaluation method described later is excellent or good. In particular, at the stage of the flame resistant polymer, the shape and form of the polymer changes depending on the isolation conditions, and the properties as flame resistance are likely to vary considerably. Therefore, a method of evaluating after molding into a certain shape is adopted. The flame resistance performance of a flame resistant molded article such as a flame resistant fiber obtained by shaping and molding a flame resistant polymer can also be measured by specific flame resistance evaluation means shown in the examples described later.

  The flame resistant polymer in the present invention is usually the same as or similar to the chemical structure of what is called a flame resistant fiber or a heat resistant fiber, heated in the air using a polyacrylonitrile-based polymer, petroleum, coal, etc. Examples thereof include those obtained by oxidizing a pitch raw material based on the above, phenol resin precursors, and the like. A polyacrylonitrile-based polymer is preferably used as the precursor polymer from the viewpoint of easy solution.

  If a polyacrylonitrile polymer is used as a precursor, the structure of the flame resistant polymer is not completely clear, but a document analyzing acrylonitrile flame resistant fibers (Journal of Polymer Science, Part A: Polymer) Chemistry Edition) (J. Polym. Sci. Part A: Polym. Chem. Ed.), 1986, Vol. 24, p. 3101) is considered to have a naphthyridine ring, an acridone ring, or a hydrogenated naphthyridine ring structure generated by a nitrile group cyclization reaction or oxidation reaction, and is generally called a ladder polymer because of its structure. Of course, even if an unreacted nitrile group remains, there is no problem as long as flame resistance is not impaired, and even if a minute amount of cross-linking is generated between molecules, there is no problem as long as dispersibility is not impaired. From this viewpoint, the polyacrylonitrile-based polymer may be linear or branched. Moreover, you may use what contains other copolymerization components, such as an acrylate, a methacrylate, and a vinyl compound, in the frame | skeleton at random or as a block.

  The molecular weight of the flame resistant polymer may be a molecular weight having a viscosity according to the molding method, but the mass average molecular weight (Mw) of the precursor polymer measured by gel permeation chromatography (GPC) is 1,000 to 1,000,000. Preferably there is. When the mass average molecular weight of the precursor polymer is lower than 1000, the time required for flame resistance can be shortened, but the intermolecular interaction such as hydrogen bonding between the flame resistant polymers is weakened. Is difficult to achieve. On the other hand, if the mass average molecular weight of the precursor polymer exceeds 1,000,000, the time required for flame resistance becomes long, so the production cost becomes high, or the molecular interaction due to hydrophobic bonds between the flame resistant polymers becomes too strong, It may gel during cooling, making it difficult to obtain fluidity of the dispersion at the forming temperature. The mass average molecular weight of the precursor polymer is more preferably 10,000 to 500,000, still more preferably 20,000 to 300,000.

When a polyacrylonitrile-based polymer is used as a precursor polymer, the structure is not completely elucidated, but it is considered that a naphthidine ring or an acridone ring is the main structure as described above. As the flame resistant polymer, it is preferable to measure 13-C of the solution with a nuclear magnetic resonance apparatus (NMR) and to have a signal at 150 to 200 ppm, and 1600 cm ⁻¹ by infrared spectroscopic measurement (IR). It is preferable to have a maximum absorption peak in the vicinity. When it has a peak in the said range by both measuring methods, it can be said that it is a flame resistant polymer having particularly high heat resistance.
In the present invention, the method for removing the dispersion medium from the dispersion containing the shaped flame resistant polymer is not particularly limited. For example, the dispersion medium is evaporated from the dispersion containing the flame resistant polymer shaped by heating or decompression. And a method of immersing a dispersion containing a flame resistant polymer shaped in the coagulation liquid and extracting the dispersion medium into the coagulation liquid. In the present invention, a method of extracting the dispersion medium into the coagulation liquid, which is easy to control and has high process productivity, is preferable.

  As the coagulation liquid, a liquid which is a poor solvent for the flame resistant polymer and is compatible with the dispersion medium is preferably used. In the present invention, it is preferable to use an aqueous coagulation liquid as the coagulation liquid. In order to facilitate recovery of the extracted dispersion medium, water and the same type of solvent as the dispersion medium used in the dispersion containing the flame resistant polymer are used. It is preferable to use a mixed system coagulation liquid. In these coagulation liquids, a solvent other than the dispersion medium used in the dispersion containing the flame resistant polymer may be mixed. From the viewpoint of solvent recovery, water and a dispersion containing the flame resistant polymer are used. It is preferable that the coagulation liquid is composed of only the dispersion medium and the same type of solvent. The mixing ratio of water and solvent in the coagulation liquid is preferably 1: 9 to 9: 1, more preferably 2: 8 to 8: 2, and further preferably 3: 7 to 7: 3. . By setting such a mixing ratio, it is possible to control the coagulation speed, and it becomes possible to control the characteristics according to the application with the coagulation liquid. The coagulation liquid may contain an inorganic salt as a compound that facilitates extraction of the dispersion medium, a pH adjuster, a process treatment agent, a dispersion reaction accelerator, and the like.

  In the present invention, as a method for shaping a dispersion containing a flame resistant polymer into a fiber, a wet spinning method, a dry wet spinning method, a dry spinning method, a flash spinning method, an electrospinning spinning method, a spunbond method, a melt blow method, and Methods such as centrifugal spinning can be employed. Among them, the wet spinning method and the dry wet spinning method have high productivity and are preferably applied in the present invention. In particular, the wet spinning method has high productivity because the dispersion medium starts to be removed immediately after the dispersion containing the flame resistant polymer is formed, and the fiber is run at a low speed even if the fiber strength immediately after the formation is low. Easy to handle. The wet spinning method referred to here is a method in which a dispersion containing a flame resistant polymer is introduced to a die having a plurality of holes after measurement and filtration, and then the pressure applied to the dispersion containing the flame resistant polymer is released from the die holes. It is a method of discharging and shaping and immediately coagulating with a coagulating liquid. Dry-wet spinning is a method in which a dispersion containing a flame resistant polymer is ejected from a die hole, shaped, run in a gas phase, and then solidified with a coagulating liquid.

  As the base material used here, SUS, gold, platinum or the like can be appropriately used. In addition, before the dispersion containing the flame resistant polymer flows into the die hole, a sintered filter of inorganic fibers or synthetic fibers, for example, woven fabrics, knitted fabrics and nonwoven fabrics made of polyester fibers or polyamide fibers, are used as a filter. Filtration or dispersion of the polymer-containing dispersion is a preferred embodiment from the viewpoint of reducing variation in the cross-sectional area of the single fiber in the resulting flame-resistant fiber assembly.

  The diameter of the nozzle hole is preferably in the range of 0.01 to 0.5 mm, and the hole length is preferably in the arbitrary range of 0.01 to 1 mm. Moreover, the number of cap holes can be arbitrarily set within a range of preferably 10 to 1000000. The hole arrangement may be arbitrary, such as a staggered arrangement, or may be divided in advance so as to facilitate separation.

In the first step of coagulation, the temperature of the coagulation liquid can be any temperature above the freezing point of the coagulation liquid and below the boiling point, and can be appropriately adjusted according to the coagulation property and processability of the flame resistant polymer.
In order to make the structure of the coagulated yarn dense, the temperature of the coagulating liquid is preferably in the range of 20 ° C. or higher and 40 ° C. or lower. Further, after the second step of coagulation, any temperature between the freezing point and the boiling point of the coagulating liquid is possible, but when water is used as the coagulating liquid, the temperature of the coagulating liquid is in the range of 60 ° C to 85 ° C. It is preferable that By setting the temperature of such a coagulating liquid, the dispersion medium remaining in the first step is efficiently extracted. Moreover, it is preferable that the density | concentration of the poor solvent in coagulation liquid increases as it passes through a coagulation process.

  It is preferable to apply an oil agent as will be described later to the fiber yarn in the water-swollen state after being washed and stretched. The method of applying the oil may be selected and used as appropriate, considering that the oil can be uniformly applied to the inside of the fiber yarn. Specifically, the fiber yarn is immersed in the oil bath, and the running fiber Means such as spraying and dripping onto the yarn are employed. The concentration of the oil agent applied here is preferably in the range of 0.01 to 20% by weight. Here, the oil agent is composed of, for example, a main oil agent component such as silicone and a diluent component for diluting it, and the oil agent concentration is a content ratio of the main oil agent component to the whole oil agent.

  The adhesion amount of the oil component is preferably in the range of 0.1 to 5% by weight, more preferably in the range of 0.3 to 3% by weight, with respect to the dry weight of the fiber yarn. More preferably, it is the range of 0.5 to 2 weight%. If the adhesion amount of the oil component is too small, fusion between single fibers occurs, and if it is too large, the resulting carbon fibers may be burned unevenly and the tensile strength of the resulting carbon fibers may be reduced.

  The fiber yarn can be dried by directly contacting the fiber yarn with a plurality of dry-heated rollers, sending hot air or steam to the fiber yarn, or applying infrared or high-frequency electromagnetic waves to the fiber yarn. An irradiation method, a reduced pressure method, and the like can be appropriately selected and combined. Usually, when sending hot air, it can carry out by making it flow parallel or orthogonal to the running direction of a fiber yarn. Far-infrared rays, mid-infrared rays, and near-infrared rays can be used as the radiant heating type infrared rays, and irradiation with microwaves can also be selected. The drying temperature can be arbitrarily set within a range of about 50 to 450 ° C., but generally it takes a long time at a low temperature and can be dried in a short time at a high temperature.

  In the present invention, a molded body such as a fiber obtained by forming a dispersion containing a flame resistant polymer may contain many voids. In many cases, it is desirable to further increase the mechanical strength of the compact. As a means for improving the mechanical strength, it is preferable to go through a sintering / firing process for closing the voids by heat-treating the molded product obtained as described above.

  In the above process, conditions such as the temperature profile and the process passing speed depend on the material, but it is preferably heat-treated at a temperature of 50 ° C. lower than the softening point temperature of the molded product, more preferably processed at the softening point or higher. Is done. When the processing temperature is lower than the softening point temperature of −50 ° C., it is difficult to close the voids contained in the molded product. Moreover, although there is no upper limit in particular in temperature, when a molded article becomes soft and it is hard to maintain a shape, it is preferable to raise process temperature in several steps, or to raise continuously.

  Moreover, when the softening point is lowered with a plasticizer, sintering and sintering can be performed while suppressing the thermal decomposition reaction. The plasticizer component may be included in the dispersion containing the flame resistant polymer in advance, but it is applied between the solidification process and the sintering / firing process from the viewpoint of recovery of the dispersion medium containing the flame resistant polymer. It is preferred that The plasticizer is not particularly limited as long as it lowers the softening point, but is preferably a liquid from the viewpoints of uniform application to a molded product and dispersion into a dispersion. Among them, it is preferable to use water that is environmentally friendly and highly safe, and it is a more preferable embodiment that water containing a surfactant is used in order to improve adhesion to the yarn.

  In the present invention, the chemical structure of the molded product may be changed in the heat treatment for forming a molded product such as a fiber into a sintered / fired product. For example, when the flame resistant polymer is a condensation polymer compound, the molecular weight of the flame resistant polymer is increased by solid phase polymerization in a vacuum atmosphere, or in the case of a flame resistant polymer having an acridone skeleton or a pyrimidine skeleton, it has a graphite structure. Or may change. These changes occur after the voids included in the molded article are reduced by heat treatment. By doing so, it is possible to obtain a sintered / fired body having few voids and excellent mechanical properties.

  In the present invention, the heat treatment for forming the molded product into a sintered / baked product may not involve a change in the chemical structure of the molded product. For example, in the case of silica or titania obtained by the sol-gel transition method, by performing heat treatment at an appropriate temperature, the gap between particles is substantially blocked, and an appropriate sintered / fired product can be obtained. Become.

  Further, in the heat treatment step during firing and sintering, the molded product may be subjected to deformation such as stretching or compression. By these deformations, the form of the obtained fired / sintered product becomes more preferable, and the mechanical properties and other properties can be improved.

  In the present invention, the formed flame-resistant fiber may take the form of a fiber assembly such as a multifilament. In the present invention, the carbon fiber aggregate can be obtained by subjecting the flame resistant fiber aggregate to high temperature heat treatment in an inert atmosphere, so-called carbonization treatment. The carbon fiber aggregate can be obtained by heat-treating the flame resistant fiber aggregate of the present invention at a maximum temperature in an inert atmosphere, preferably in the range of 300 ° C. or more and less than 2000 ° C. More preferably, the direction below the maximum temperature is preferable in the order of 800 ° C. or more, 1000 ° C. or more, and 1200 ° C. or more, and the direction above the maximum temperature can be 1800 ° C. or less. Further, the obtained carbon fiber aggregate can be further heated in an inert atmosphere at a temperature of preferably 2000 to 3000 ° C. to obtain a carbon fiber aggregate having a developed graphite structure.

  The strength of the obtained carbon fiber aggregate is preferably in the order of 100 MPa or more, 200 MPa or more, and 300 MPa or more, and the higher strength is appropriate in the order of 10,000 MPa or less, 8000 MPa or less, and 6000 MPa or less. If the strength is too low, it may not be used as a reinforcing fiber. The higher the strength, the better, but 1000 MPa is often sufficient for the purposes of the present invention.

Further, the fiber diameter of the single fibers constituting the carbon fiber aggregate is preferably from 1nm~7 × ¹⁰ 4 nm, more preferably from 10.about.5 × ¹⁰ 4 nm, more preferably 50 to 10 ⁴ nm It is. If the fiber diameter is less than 1 nm, the fiber may break easily, and if it exceeds 7 × 10 ⁴ nm, defects tend to occur.

  The specific gravity of the carbon fiber aggregate obtained in the present invention is preferably 1.3 to 2.4, more preferably 1.6 to 2.1, and still more preferably 1.6 to 1. 75. If the specific gravity is less than 1.3, the fiber may be easily broken, and if the specific gravity exceeds 2.4, defects tend to occur. The specific gravity can be measured by a liquid immersion method or a floatation method. Here, the carbon fiber single fiber may include a hollow portion like a hollow fiber. In this case, the hollow portion may be continuous or discontinuous.

  The obtained carbon fiber aggregate can be subjected to electrolytic treatment for surface modification. As an electrolytic solution used for the electrolytic treatment, an acidic solution such as sulfuric acid, nitric acid and hydrochloric acid, an alkali such as sodium hydroxide, potassium hydroxide and tetraethylammonium hydroxide or a salt thereof can be used as an aqueous solution. Here, the amount of electricity required for the electrolytic treatment can be appropriately selected depending on the carbon fiber to be applied.

  The electrolytic treatment can optimize the adhesion between the carbon fiber material and the matrix in the resulting composite material, resulting in a brittle breakage of the composite material due to excessive adhesion and a decrease in tensile strength in the fiber length direction. The problem is that the tensile strength in the longitudinal direction of the fiber is high, but the adhesive properties with the resin are poor, and the strength property in the transverse direction of the fiber is not expressed, and the resulting composite material has a balanced strength Characteristic comes to be expressed.

  Thereafter, a sizing agent can also be added to impart convergence to the resulting carbon fiber aggregate. As the sizing agent, a sizing agent having good compatibility with the resin can be appropriately selected according to the type of resin used.

  Specifically, when a carbon fiber aggregate is obtained from a flame resistant polymer via a flame resistant fiber aggregate, the flame resistant polymer-containing solution is spun into a flame resistant fiber aggregate, and then continuously without a winding step until carbonization. Can be manufactured as a continuous process including a surface treatment and a sizing agent application step.

  From the viewpoint of cost reduction, it is possible to adopt a method of continuously producing from a flame resistant polymer to a carbon fiber aggregate in one process.

  Next, the present invention will be described specifically by way of examples. Each physical property value and characteristic in each example are measured by the following methods.

<Evaluation of spinnability>
The dispersion containing the flame resistant polymer adjusted to a temperature of 30 ° C. was passed through a sintered filter in a coagulation bath consisting of 55 parts by weight of dimethyl sulfoxide and 45 parts by weight of water adjusted to a temperature of 30 ° C. After that, from a base having a hole diameter of 0.05 mm and 1000 holes, it is discharged at a speed of 10 cc per minute, and the fiber yarn shaped by this is wound with a driving roller at a speed of 1.5 meters per minute for 1 hour. When the number of single fiber pieces found in the coagulation bath was measured during this time, the case where the number of single fiber pieces was 5 or less was marked ◎, and the number of single fiber pieces was 6 The case where the number is 10 or less is evaluated as ◯, and the case where the number of single fibers is 11 or more is evaluated as ×.

<Isolation and concentration measurement of flame resistant polymer>
The dispersion containing the flame resistant polymer was weighed and about 4 g was placed in 500 ml water and boiled. Once the solid was removed, it was again placed in 500 ml of water to bring it to a boil. The remaining solid content was placed on an aluminum pan and dried in an oven at a temperature of 120 ° C. for 1 hour to isolate the flame resistant polymer. The isolated solid was weighed and the concentration was determined by calculating the ratio with the weight of the original dispersion containing the flame resistant polymer.

<NMR measurement of flame resistant polymer>
The NMR spectrum of the flame resistant polymer was measured using a measurement nuclear frequency of 67.9 MHz, a spectrum width of 15015 kHz, and a spectrum of a solvent known at room temperature as an internal standard. GX-270 manufactured by JEOL Ltd. was used as the apparatus.

<IR (Infrared Spectrophotometer) Measurement>
FT-IR measurement using a tablet processed by a tablet molding machine after removing the solvent from the flame resistant polymer in high-temperature hot water and freeze-pulverized 2 mg and 300 mg of infrared photoluminescent KBr in a mortar It measured using the apparatus (made by Shimadzu Corp.).

<Measurement of specific gravity of fiber>
An automatic specific gravity measuring device using an immersion method with an electronic balance was made by itself and measured according to JIS Z 8807 (1976). Ethanol was used as a liquid, and a sample was put into the liquid for measurement. Prior to charging, the sample was sufficiently wetted in a separate bath using ethanol, and a bubble removal operation was performed.

<Fiber flame resistance evaluation method>
Using a bundle of 1500 single fibers, a sample length of 30 cm and heating in a Meckel burner flame with a height of 160 mm and an inner diameter of 20 mm for 10 seconds according to JIS L 1091 (1977) Flame time and carbonization length are obtained, and flame resistance is evaluated from these values according to the following criteria.
[Excellent flame resistance]: Afterflame time is 10 seconds or less, and carbonization length is 5 cm or less.
[Good flame resistance]: After-flame time is 10 seconds or less, and carbonization length is 10 cm or less.
[With flame resistance]: Afterflame time is 10 seconds or less, and carbonization length is 15 cm or less.
[Bad]: The after flame time exceeds 10 seconds, or the carbonization length exceeds 15 cm.
The number of measurements is n = 5, and the state with the largest number of hits is the flame resistance of the sample. If the evaluation is not determined, an evaluation of n = 5 is further added, and measurement is repeated until the evaluation is determined.

<Tensile strength, tensile modulus and tensile elongation of single fiber>
In any case, a tensile test is performed according to JIS L1013 (1999). A single piece of fiber having a length of 25 mm for each 5 mm width is fixed to a piece of paper having a smooth surface and gloss, with both ends loosely stretched with an adhesive so that the sample length is about 20 mm. The sample is attached to the grip of a fiber tensile tester, a piece of paper is cut near the top grip, and the sample length is 20 mm and the tensile speed is 20 mm / min. The number of measurements is n = 50, and the average values are the tensile strength, tensile modulus, and tensile elongation. In the examples, an Instron model 1125 was used as a fiber tensile tester.

Example 1
A solution comprising 10 parts by weight of acrylonitrile homopolymer, 3.5 parts by weight of monoethanolamine, 8.0 parts by weight of orthonitrotoluene and 75.5 parts by weight of dimethyl sulfoxide was stirred at a temperature of 150 ° C. for 8 hours and then cooled to room temperature. Thus, a flame resistant polymer dispersion in which the flame resistant polymer was dispersed was obtained. Next, 2.5 parts by weight of ammonium benzoate as a salt was added to the flame resistant polymer dispersion at room temperature and stirred to obtain a dispersion containing the flame resistant polymer. The concentration of the flame resistant polymer in the obtained dispersion containing the flame resistant polymer is 12.1% by weight, and the isolated flame resistant polymer is analyzed by 13C-NMR, and is clearly a precursor polymer at 160 to 180 ppm. There was a peak derived from a flame resistant polymer that was not confirmed with polyacrylonitrile, solvent or modifier. Further, when analyzed by IR, a clear peak was present at 1600 cm ⁻¹ . When the dispersion containing the flame resistant polymer was continuously spun for 1 hour by the method of <Spinnability Evaluation>, the fluff (single fiber breakage) in the coagulation bath was zero, and the coagulation evaluation was ◎. The obtained fiber yarn was stretched 1.3 times in a warm water bath at a temperature of 80 ° C. while almost replacing the solvents with water. Then, it was further washed through a roller in a warm water bath at a roller speed of 10 m / min. Then, after giving an amino silicone oil agent, it dried for 3 minutes at the temperature of 220 degreeC in a hot-air circulating furnace. The specific gravity of the dried fiber yarn was 1.30, and the elongation was 3%. Further, it was stretched 1.5 times at a temperature of 300 ° C. in a hot air circulating furnace and simultaneously heat treated for 3 minutes to obtain a flame resistant fiber bundle.

  The fineness of the single fiber in the obtained flame resistant fiber bundle was 1.0 dtex, the strength was 2.3 g / dtex, and the elongation was 18%. When the flame resistance was evaluated, it turned out to be red hot without burning, and it was found to have excellent flame resistance with a carbonization length of 1 cm. Furthermore, the flame resistant fiber bundle obtained from the flame resistant polymer was pre-carbonized at a temperature of 300 to 800 ° C. in a nitrogen atmosphere, and then carbonized at a temperature of 1400 ° C. in a nitrogen atmosphere to obtain a carbon fiber bundle. The obtained carbon fiber bundle had a strength of 3000 MPa, an elastic modulus of 210 GPa, and a specific gravity of 1.78.

(Example 2)
The experiment was performed in the same manner as in Example 1 except that 3.0 parts by weight of ammonium acetate was used as the salt. The concentration of the flame resistant polymer in the obtained dispersion containing the flame resistant polymer is 12.1% by weight, and the isolated flame resistant polymer is analyzed by 13C-NMR, and is clearly a precursor polymer at 160 to 180 ppm. There was a peak derived from a flame resistant polymer that was not confirmed with polyacrylonitrile, solvent or modifier. Further, when analyzed by IR, a clear peak was present at 1600 cm ⁻¹ . The dispersion containing the flame resistant polymer was spun continuously for 1 hour by the above-described <Spinnability evaluation> method. As a result, there was one fluff in the coagulation bath and the coagulation evaluation was ◎. The strength of the carbon fiber bundle obtained from this was 3100 MPa, the elastic modulus was 195 GPa, and the specific gravity was 1.75.

(Example 3)
The experiment was performed in the same manner as in Example 1 except that 1.0 part by weight of sodium citrate was used as a salt. The concentration of the flame resistant polymer in the dispersion containing the obtained flame resistant polymer is 12.4% by weight. When the isolated flame resistant polymer is analyzed by 13C-NMR, it is clearly a precursor polymer at 160 to 180 ppm. There was a peak derived from a flame resistant polymer that was not confirmed with polyacrylonitrile, solvent or modifier. Further, when analyzed by IR, a clear peak was present at 1600 cm ⁻¹ . When the dispersion containing the flame resistant polymer was continuously spun for 1 hour by the above-described <spinning evaluation> method, the fluff in the coagulation bath was 8 pieces and the coagulation evaluation was good.

(Comparative Example 1)
The concentration of the flame resistant polymer in the obtained flame resistant polymer dispersion obtained by performing the experiment in the same manner as in Example 1 except that no salt was added was 12.6% by weight, and the isolated flame resistant polymer was analyzed by 13C-NMR. As a result, a peak derived from a flame resistant polymer that was not clearly confirmed by polyacrylonitrile as a precursor polymer, a solvent, or a modifier was present at 160 to 180 ppm. Further, when analyzed by IR, a clear peak was present at 1600 cm ⁻¹ . When this flame resistant polymer dispersion was continuously spun for 1 hour by the above method, the fluff in the coagulation bath was fifteen and the coagulation evaluation was x.

  When the dispersion containing the flame resistant polymer of the present invention is shaped into a dispersion containing the flame resistant polymer, the separation from the discharge port is remarkably good. Can be suppressed. Furthermore, since the dispersion containing the flame-resistant polymer of the present invention is easily separated from the die, the die hole density can be increased and space can be saved, so that the production efficiency is improved.

Claims (7)

  A dispersion containing a flame resistant polymer, wherein the salt and the flame resistant polymer are dispersed in a dispersion medium.   The dispersion containing a flame resistant polymer according to claim 1, wherein the concentration of the salt is in the range of 0.1 to 10 parts by weight with respect to the total amount of the dispersion containing the flame resistant polymer.   The dispersion containing a flame resistant polymer according to claim 1 or 2, wherein the flame resistant polymer is obtained by heat-treating an acrylonitrile-based polymer.   The dispersion containing the flame resistant polymer according to any one of claims 1 to 3, wherein the dispersion medium is a polar solvent.   The dispersion containing a flame resistant polymer according to any one of claims 1 to 4, wherein the cationic species of the salt is an ammonium ion.   A flame resistant fiber formed by shaping a dispersion containing the flame resistant polymer according to claim 1.   A carbon fiber obtained by carbonizing the flame resistant fiber according to claim 6.