KR101239424B1 - Preparation method for carbon fiber precursor - Google Patents

Abstract

It is possible to obtain high strength / high elastic carbon fibers by preventing macrofiber adhesion and surface defects by preventing adhesion between short fibers in the flameproofing process, and providing a method of manufacturing a carbon fiber precursor which can improve processability and workability. do.

Description

Production method of carbon fiber precursors {PREPARATION METHOD FOR CARBON FIBER PRECURSOR}

The present invention relates to a carbon fiber precursor and a method of manufacturing the same.

Carbon fiber is excellent in strength, inelasticity, and the like, and is widely used in general industrial as well as sporting goods, aviation, and space industry. Carbon fibers made from acrylonitrile-based polymers, so-called polyacrylonitrile (PAN) -based carbon fibers, are particularly widely used as raw materials for carbon fibers because of their excellent strength characteristics. Recently, more than 90% of all carbon fibers are PAN-based carbon fibers. The PAN-based carbon fiber has been developed as a carbon electrode material for a secondary battery, a carbon film, and the like, and its application field is also expanding. In order to expand the use of carbon fibers, it is necessary to reduce manufacturing costs and to improve the performance of carbon fibers.

In order to improve the performance of carbon fibers, various methods for improving the physical properties of carbon fiber precursors have been reported. In order to reduce the foreign matter, macrovoids, etc. in the fiber, a technique for enhancing the filtration of the monomer or polymer stock solution has been developed. Techniques for controlling the tension of fibers, etc. have been developed.

In preparing the precursor fiber, and flame-resistant and carbonized it at a high temperature to produce the carbon fiber, the precursor short fibers are easily adhered, and the strength of the fiber is lowered due to defects such as short fiber adhesion and fiber surface wounds. have. In order to suppress such short fiber adhesion, the use of various oil agents has been proposed. For example, in place of non-silicone oils, such as higher alcohol, the use of the silicone-based oils excellent in heat resistance, mold release property, smoothness, etc. is proposed. However, the formation of macro defects of fibers can be suppressed by the filtration of the stock solution as described above, the suppression of generation of fiber surface defects due to improved guides, and the prevention of short-term adhesion due to the use of high-performance emulsions. In particular, it is difficult to improve the compactness.

The present invention comprises the steps of dissolving an acrylonitrile-based polymer in an organic solvent to prepare a polymer solution; Spinning the polymer solution by wet or wet spinning method to obtain precursor fibers; And extending the spun precursor fiber, wherein the amount of solvent remaining in the carbon fiber precursor is 0.1 to 2.0% by weight.

The extending step may include extending the spun precursor fiber to hot water of 60 ° C. or higher; Imparting an emulsion comprising at least one selected from the group consisting of a silicone-based emulsion, a modified epoxy emulsion, and an emulsion comprising an ammonium compound; Dry densification using a heating roller of 150 ° C. or higher; And stretching under hot pressurized steam.

The precursor fiber extended by the extension step has a total draw ratio of 7 to 20, and the short fiber fineness of the carbon fiber precursor is 0.5 to 2 dtex.

In preparing the polymer solution, at least one selected from the group consisting of dimethyl sulfoxide, dimethyl formamide, and dimethyl acetamide may be used as the organic solvent.

In the preparation of the polymer solution, the acrylonitrile-based polymer and the extension and densification promoting component in the spinning process and the flame resistance promoting component and oxygen permeation promoting component in the flameproofing process can be polymerized together.

The extension and densification facilitating component comprises a carboxyl group or an amine group and is selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid and alkyl esters thereof, acrylamide, methacrylamide, dimethylacrylamide At least one selected may be used.

The flame resistance promoting component may use at least one selected from the group consisting of octylamine, dodecylamine, laurylamine, dioctylamine, dialkylamine, trioctylamine, trialkylamine, ethylenediamine and hexamethylenediamine.

The present invention also provides a carbon fiber precursor prepared by the above method.

According to the production method of the present invention, the affixes in the dry densification step and the secondary stretching step decrease, so that the quality of the precursor fiber is excellent, and a carbon fiber precursor having a small change in physical properties of the precursor fiber over time can be obtained. . In addition, it is possible to obtain high strength / high elastic carbon fibers by preventing the interfiber adhesion between the short fibers in the flameproofing process to reduce the macroscopic affixation and surface defects, and improve processability and workability.

Method for producing a carbon fiber precursor according to an embodiment of the present invention, dissolving an acrylonitrile-based polymer in an organic solvent to prepare a polymer solution; Spinning the polymer solution by wet or wet spinning method to obtain precursor fibers; And extending the spun precursor fiber, wherein the remaining solvent amount of the carbon fiber precursor is 0.1 to 2.0 wt%.

The carbon fiber precursor prepared according to the invention is obtained from an acrylonitrile-based polymer, the properties of which are basically dependent on the composition of the acrylonitrile-based polymer. The main component of the acrylonitrile-based polymer used in the present invention is an acrylonitrile unit, and the content of the acrylonitrile unit is preferably 90% by weight or more, more preferably 95% by weight based on the total acrylonitrile-based polymer. Or more, such as 95 to 99% by weight. Here, when the content of the acrylonitrile unit is too small, there is a fear that the mechanical properties of the carbon fibers are lowered, such as the strength of the carbon fibers obtained in the firing step is lowered.

The acrylonitrile-based polymer is, as necessary, at least one copolymerization component (other auxiliary component other than acrylonitrile), a unit containing a densification accelerator component in the spinning process, an extension promoter component, and a flame resistance in the flameproofing process. It may further include a unit comprising an accelerating component, a unit including an oxygen permeation promoting component, the content is preferably less than 10% by weight, more preferably less than 5% by weight relative to the total acrylonitrile-based polymer Such as 1 to 5% by weight. The structural unit serving as the densification promoting component is produced by copolymerization of a vinyl compound monomer having a hydrophilic functional group such as a carboxyl group, a sulfone group or an amide group, and examples of the monomer including a densification promoting component having a double carboxyl group include acrylic acid and meta. Crylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid, these alkyl esters (methyl acrylate, etc.) etc. can be illustrated, Especially acrylic acid, methacrylic acid, and itaconic acid are preferable. Moreover, allyl sulfonic acid, metharyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, vinyl sulfonic acid, a sulfopropyl methacrylate etc. are mentioned as a specific example of the densification promotion component which has the said sulfonic group. Acrylamide, methacrylamide, dimethyl acrylamide, etc. can be used as a specific example of the structural unit of the densification promotion component which has the said amide group. In addition, in order to improve the oxygen permeability between single yarns in a flame resistant furnace, alkyl amines such as octylamine, dodecylamine and lauryl amine, dialkyl amines such as dioctylamine, trialkyl amines such as trioctylamine, Diamine components, such as ethylenediamine and hexamethylenediamine, can be used. Among these, in order to improve the uniformity of superposition | polymerization, it is preferable to use the component which has solubility with respect to a polymerization solvent, a medium, a spinning solvent, etc. In addition, the unit including the oxygen permeation promoting component may be introduced by copolymerization of an alkyl ester of one unsaturated carboxylic acid structure, such as ethyl methacrylate. When such an auxiliary component (comonomer) and a main component are subjected to aqueous suspension polymerization according to a conventional method, an acrylonitrile copolymer can be obtained.

In order to prepare a carbon fiber precursor from the acrylonitrile-based polymer, the acrylonitrile-based polymer is dissolved in an organic solvent to prepare a polymer solution or a dope (dark liquid such as glue).

As the organic solvent, at least one selected from the group consisting of dimethyl sulfoxide, dimethyl formamide and dimethyl acetamide may be used as a solvent capable of dissolving the acrylonitrile polymer. Can be. In addition to the solvent, a conventional organic solvent or inorganic solvent capable of dissolving an acrylonitrile polymer such as dimethyl acetate, zinc chloride aqueous solution, and nitric acid may be used, and may be used in an amount of 10 to 30 parts by weight based on 100 parts by weight of the acrylonitrile polymer. Can be. If the amount of the organic solvent used is too high or too low, the polymer may be difficult to spin or voids may be inefficiently performed. The polymer solution thus prepared is 15 to 25% by weight.

After spinning the polymer solution by wet or wet spinning method to obtain precursor fibers, the spun precursor fibers are then extended. The extending step, after extending the spun precursor fiber to hot water at 60 ℃ or more, imparts an emulsion comprising at least one selected from the group consisting of a silicone-based emulsion, a modified epoxy emulsion, and an emulsion containing an ammonium compound, 150 After drying and densifying using a heating roller of 占 폚 or higher, stretching is performed under high pressure pressurized steam.

The precursor fiber extended by the extension step has a total draw ratio of 7 to 20, and the short fiber fineness of the carbon fiber precursor is 0.5 to 2 dtex.

The present invention also provides a carbon fiber precursor prepared by the above method. Since the precursor fiber has a residual solvent amount of 0.1 to 2.0% by weight, high quality carbon fibers may be manufactured by preventing adhesion between short fibers in a dry densification step, a second extension step, a flameproofing step, and a carbonization step.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples.

Acrylonitrile and itaconic acid were injected into the polymerization reactor with 98% by weight and 2% by weight, respectively, together with dimethyl sulfoxide as a solvent. The solvent was injected so that the concentration of the monomer was 22% by weight based on the total amount of the injection, 0.1% by weight of azobisisobutyronitrile as an initiator and 0.2% by weight of thio glycol as a polymerization degree regulator as an initiator. The injection was allowed to complete in 2 hours and then stirred to prepare a uniform solution. The polymerization was carried out at 65 ° C. for 14 hours to prepare an acrylonitrile polymer solution containing 20 wt% of a copolymer having an inherent viscosity of 2.0.

The polymer solution, which was filtered through a 5 μm filter in one stage, was stored at 50 ° C., and a gap of 5 mm was used in a coagulation bath in which the concentration of dimethyl sulfoxide was adjusted to 40 wt% and 10 ° C. using a diameter of 0.12 mm and 4000 nozzles. ) To coagulate the precursor fibers by wet and dry spinning.

The obtained coagulated sand was washed by applying a nip roller pressure of 2 kgf in a multi-stage washing bath equipped with a nip roller (squeeze roller) capable of adjusting the pressure, and then extending to hot water of 60 ° C. or higher, and then applying a silicone emulsion. After giving a modified epoxy emulsion and an emulsion containing an ammonium compound and drying and densifying using a heating roller of 150 ° C. or higher, stretching under high pressure pressurized steam, the total draw ratio is 7 to 20, and short fiber fineness is 0.5 to A precursor for carbon fiber, which is 2 dtex, was obtained.

10% shrinkage at 240 to 250 ℃ temperature using the precursor for carbon fiber to make a flame resistant yarn having a fiber specific weight of 1.35, 3% extension in a nitrogen atmosphere of 300 to 500 ℃ temperature, 5 under a nitrogen atmosphere of 1350 ℃ temperature % Shrinkage to obtain carbon fiber.

The affixes of the obtained flame resistant yarns and carbon fibers were evaluated, and carbon fiber strand strength was measured.

It was prepared in the same manner as in Example 1 except that a nip roller pressure of 3 kgf was added to the washing bath.

It was prepared in the same manner as in Example 1 except that a nip roller pressure of 1 kgf was applied in a washing bath.

Comparative example  One

It was prepared in the same manner as in Example 1 except that a nip roller pressure of 4 kgf was added to the washing bath.

Comparative example  2

It was prepared in the same manner as in Example 1 except that a nip roller pressure of 0.5 kgf was applied in the washing bath.

Measurement of residual solvent

The precursor fiber is placed in a container, and a predetermined amount (X (mL)) of distilled water is added to reflux for 30 minutes. Liquid chromatography is used to measure the concentration of organic solvent (C (ppm)) in distilled water. Precursor fiber in distilled water was dried for 2 hours at 105 ℃ using a hot air dryer to determine the weight (W (g)).

The remaining solvent is calculated by the following equation.

In Examples 1 to 3 and Comparative Examples 1 and 2, the amount of remaining solvent and the number of macroscopic fibers, the number of chloride-resistant weaving macrocarbons, the number of carbon fiber macropores, and the strand strength of the carbon fibers are shown in Table 1 below.

Referring to Table 1, it is very important to properly control the residual solvent amount by adjusting the pressure of the water nip roller. In general, the higher the pressure of the flush nip roller, the smaller the amount of remaining solvent to reduce the number of macroffixes and the higher the strength of carbon fiber strands.If the pressure is too high, the fiber damage and the lubricity during stretching by the solvent is lowered, the strength is lowered. . However, at this time, the pressure of the nip roller is not an absolute index because the effect of the degree can vary depending on the individual process specificity.

Claims (9)

Dissolving an acrylonitrile-based polymer in an organic solvent to prepare a polymer solution;
Spinning the polymer solution by wet or dry spinning to obtain precursor fibers; And
In the method of producing a carbon fiber precursor comprising the step of extending the spun precursor fiber,
In the step of preparing the polymer solution, the acrylonitrile-based polymer and the extension and densification promoting component in the spinning process and the flame resistance promoting component and oxygen permeation promoting component in the flameproofing process are polymerized together.
The remaining solvent amount of the carbon fiber precursor is 0.1 to 2.0% by weight of the production method of the carbon fiber precursor. The method of claim 1,
The extending step,
Extending the spun precursor fiber to hot water at 60 ° C. or higher;
Imparting an emulsion comprising at least one selected from the group consisting of a silicone-based emulsion, a modified epoxy emulsion, and an emulsion comprising an ammonium compound;
Dry densification using a heating roller of 150 ° C. or higher; And
Method of producing a carbon fiber precursor, characterized in that it comprises the step of stretching under high pressure pressurized steam. The method of claim 1,
The precursor fiber extended by the extension step is characterized in that the total draw ratio of 7 to 20, the carbon fiber precursor. The method of claim 1,
Method for producing a carbon fiber precursor, characterized in that the short fiber fineness of the carbon fiber precursor is 0.5 to 2 dtex. The method of claim 1,
The organic solvent is at least one selected from the group consisting of dimethyl sulfoxide (dimethyl sulfoxide), dimethyl formamide (dimethyl formamide) and dimethyl acetamide (dimethyl acetate). delete The method of claim 1,
The extension and densification-promoting component includes a carboxyl group or an amine group, and is a group consisting of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, maleic acid and alkyl esters thereof, acrylamide, methacrylamide, and dimethylacrylamide. At least one selected from, characterized in that the manufacturing method of the carbon fiber precursor. The method of claim 1,
The flameproofing promoting component is at least one selected from the group consisting of octylamine, dodecylamine, laurylamine, dioctylamine, dialkylamine, trioctylamine, trialkylamine, ethylenediamine and hexamethylenediamine , Method for producing a carbon fiber precursor. A carbon fiber precursor prepared by the method of any one of claims 1 to 5, 7 or 8.