KR20130078788A

KR20130078788A - The method of producing complex precursor multi filament and carbon fiber

Info

Publication number: KR20130078788A
Application number: KR1020110147912A
Authority: KR
Inventors: 김우철; 정종철; 진상우; 윤준영
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2013-07-10

Abstract

PURPOSE: A manufacturing method of a composite precursor multifilament for a carbon fiber and the carbon fiber are provided to replace high cost PAN-based precursor fabric by a low cost precursor (lignin-containing precursor). CONSTITUTION: A manufacturing method of composite precursor multifilament for a carbon fiber and the carbon fiber comprises a step of manufacturing a spinning solution by dissolving a polyacrylonitrile-based polymer and a lignin in a solvent; a step of spinning the composite precursor multifilament to a solidification bath by the spinning of the spinning solution including the polyacrylonitrile-based polymer and the lignin; a step of primarily elongating the composite precursor multifilament in a hot water elongating apparatus filled with hot water at 70-100 °C; a step of secondarily elongating the composite multifilament in the steam elongating machine at 110-130 °C; and a step of rolling the composite precursor multifilament.

Description

The method of producing complex precursor multi filament and carbon fiber}

The present invention relates to a composite precursor multi-filament for carbon fiber and a method for producing carbon fiber.

Since carbon fiber has higher specific strength and inelasticity than other fibers, it is a reinforcing fiber for composite materials. In addition to conventional sports and aerospace applications, carbon fiber is used in general industries such as automobiles, civil construction, pressure vessels, and windmill blades. It is widely deployed in applications, and there is a high demand for further productivity improvement and production stabilization.

Polyacrylonitrile (hereinafter sometimes abbreviated as PAN) -based carbon fiber, which is most widely used among carbon fibers, may be formed by wet spinning, dry spinning or wet spinning of a spinning solution containing a PAN polymer as its precursor. After obtaining the precursor fiber for carbon fiber, it is industrially manufactured by heating in an oxidizing atmosphere, converting it into flame resistant fiber, and carbonizing by heating in inert atmosphere. At this time, PAN fiber precursors account for 43%, oxidation stabilization 18%, carbide graphitization 13%, and other processes 11%. Particularly, when the carbon fiber is produced in the precursor, the yield is very low, which is 50% or less.

The PAN-based carbon fiber has a high raw material PAN price and process energy cost as a constraint for mass production and commercial applications.

The present invention is to provide a method for producing a carbon fiber by replacing the expensive PAN-based precursor fibers having a problem as described above as a result of the cost analysis of the carbon fiber manufacturing process with a low-cost precursor (lignin-containing precursor).

Method for producing a composite precursor multi-filament for carbon fiber of the present invention is a spinning solution manufacturing process for preparing a spinning solution by dissolving a polyacrylonitrile-based polymer and lignin in a solvent; A spinning process of spinning a spinning solution containing the polyacrylonitrile-based polymer and lignin into a coagulation bath through a spinneret as a composite precursor multifilament; A hydrothermal stretching step of primary stretching the composite precursor multifilament in a hydrothermal stretching machine including hot water at 70 to 100 ° C; A steam stretching process of second stretching the composite precursor multifilament in a steam stretching machine at 110 to 130 ° C .; And a winding-up process of winding up the composite precursor multifilament.

Here, the content ratio of the polyacrylonitrile-based polymer and lignin in the spinning solution manufacturing process is preferably 90 to 50:10 to 50 weight ratio, the lignin is preferably ash content of 0.1% by weight or less.

In addition, the winding speed in the winding process is preferably 8.0 to 15 times the spinning speed in the spinning process, the elongation is 3 to 5 times in the hydrothermal stretching process, the elongation is 1.2 to 3.0 times in the steam stretching process. Do.

In addition, it is preferable that the composite precursor multifilament finally produced has a water content of 20 to 50%.

The carbon fiber manufacturing method of the present invention by using the carbon fiber composite precursor multi-filament prepared by the above-described method for producing a composite precursor multi-filament for carbon fibers as a precursor fiber, -10 ~ -0.1% or Preliminary flameproofing step of converting to preliminary flameproof fiber by heat treatment at a temperature of 180 ~ 220 ℃ while stretching at a rate of 0.1 ~ 5%; Flameproofing step of converting the preliminary flameproof fiber to a flameproof fiber by heat treatment at a temperature of 200 ~ 300 ℃ while stretching at an elongation of -5 ~ 5%; A preliminary carbonization step of preliminary carbonization at a temperature of 300 to 800 ° C. under an inert atmosphere; And a carbonization treatment step of carbonizing at a temperature of 1000 to 3000 ° C. under an inert atmosphere.

Herein, the carbon fibers produced through the preliminary flameproofing process, the flameproofing process, the preliminary carbonization treatment, and the carbonization treatment may be -10 to 10% stretched compared to the precursor fibers during the processes. It is preferable and it is more preferable to extend | stretch 0.1-10%.

The present invention introduces a low-cost lignin (lignin is a by-product of waste from the pulp and biorefinery industries as a by-product of waste in the pulp and biorefinery industries) without using the expensive PAN precursors alone. Provided are methods for making multifilaments.

In addition, the carbon fiber composite precursor multi-filament using the above-described low-cost carbon fiber through a flameproofing process and a carbonization process is provided a method of producing a carbon fiber that can provide a low-cost carbon fiber.

Hereinafter, the present invention will be described in detail.

The composite precursor fiber for carbon fiber of the present invention consists of a polymer containing a polyacrylonitrile-based polymer (sometimes abbreviated as PAN-based polymer), wherein the polyacrylonitrile-based polymer has acrylonitrile as a main component. It means a polymer. Specifically, it means a polymer containing at least 85 mol% of acrylonitrile in all monomers.

The polyacrylonitrile-based polymer may be obtained by solution polymerization by introducing a polymerization initiator into a solution containing a monomer composed mainly of acrylonitrile (sometimes referred to as AN). Besides the solution polymerization method, suspension polymerization method or emulsion polymerization method can be applied.

Among the monomers, in addition to acrylonitrile, monomers copolymerizable with acrylonitrile may be included, which may serve to promote flame resistance, and examples thereof include acrylic acid, methacrylic acid, or itaconic acid.

After the polymerization, it usually involves a step of neutralizing by using a polymerization terminator. This serves to prevent rapid coagulation in the coagulating bath when the spinning stock solution containing the polyacrylonitrile polymer to be obtained is spun.

Usually, ammonia may be used as the polymerization terminator, but is not limited thereto.

By obtaining a polymer from the monomer which has acrylonitrile as a main component, and then neutralizing it with the above-mentioned polymerization terminator, the solution containing the polyacrylonitrile-type polymer which is a salt form with ammonium ion can be manufactured.

On the other hand, the polymerization initiator used for the polymerization is preferably an oil-soluble azo compound, a water-soluble azo compound, a peroxide, and the like, and from the viewpoint of safe handling and industrially efficient polymerization, and oxygen that inhibits polymerization during decomposition, An azo compound having no fear of occurrence is preferably used, and in the case of polymerization by solution polymerization, an oil-soluble azo compound is preferably used in view of solubility. Specific examples of the polymerization initiator include 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis (2,4'-dimethylvaleronitrile), and 2 , 2'-azobisisobutyronitrile, and the like, but are not limited thereto.

Although a preferable range changes with superposition | polymerization temperature according to the kind and quantity of a polymerization initiator, Preferably it may be 30-90 degreeC.

The solution containing the polyacrylonitrile-based polymer obtained through such a polymerization reaction has a solid content of 10 to 25% by weight of the solvent is easy to remove the solvent during spinning when applied as a spinning solution for the production of precursor fibers for carbon fibers In the case of the production process, it is possible to prevent the formation of tar and impurities generated during the flameproofing process, and may be advantageous in terms of maintaining a uniform density of the filament.

The present invention is composed of a polymer in which lignin is mixed in a composite precursor fiber for carbon fiber, where lignin is composed of three basic phenyl propane structures. Guaiacyl lignin is composed of Coniferyl alcohol and Guaiacyl-syringyl lignin is composed of Coniferyl-sinapyl alcohol. Guaiacyl lignin is composed of soft wood lignin, Coniferyl-sinapyl alcohol is composed of hard wood lignin, and herbaceous or annual plant lignin is mainly composed of p-Coumaryl alcohol.

Lignin to be used in the present invention is a by-product of waste in the pulp industry and biorefinery industry, the raw material cost is close to zero.

Herein, the content ratio of the polyacrylonitrile-based polymer and lignin in the spinning solution manufacturing process is preferably 90 to 50:10 to 50 weight ratio, and when the lignin content ratio is less than 10% by weight, the ligrin content is too high. It is low and the effect of securing the economics that can be obtained by the addition of lignin is insignificant, if it exceeds 50% by weight when spinning the spinning solution, it may cause a poor spinning.

The lignin used in the composite precursor fiber for carbon fiber of the present invention was used by hardwood lignin purification, but is not limited to hardwood lignin.

Purified lignin can be prevented from burning in a carbonization process by making ash content preferably 0.1 weight% or less. Ash contained in lignin is mostly metal cation material and can be removed using a cation exchange resin used in a pure manufacturing process.

The purified lignin powder thus obtained was added to a solution obtained by DMSO solution polymerization and stirred to completely dissolve to prepare a spinning stock solution. At this time, the total solids content in the DMSO solution (PAN + lignin) content is preferably 10 to 40% by weight, lignin in the solids can be adjusted to 10 to 50% by weight.

The solution containing the lignin thus obtained can be used as a spinning stock solution in the precursor fiber manufacturing process for carbon fibers, by spinning the spinning stock solution to obtain a carbon fiber precursor fiber.

Next, the spinning solution comprising the spinning solution containing the lignin spinning in the coagulation bath in a multifilament through the spinneret.

The spinning method of the present invention adopts a method of spinning the above-described spinning stock solution into a coagulation bath with a multifilament through a spinneret by a wet spinning method or a wet-wetting spinning method so that the radiated multifilament solidifies.

Here, the wet spinning method is a method of discharging the spinning solution from the spinneret into the coagulation bath, because the solidification proceeds with three times or more swelling occurring immediately after the spinning solution is discharged from the hole. However, even if the winding speed is increased, the spinning draft has an advantage of greatly increasing, and since the wet and dry spinning method is introduced into the coagulation bath after the spinning solution is discharged into the air (air gap) through the spinneret, surface crystallization in the air gap is achieved. Since it is directed to the coagulation bath after being advanced, the actual spinning draft rate can be absorbed in the stock solution in the air gap to enable high speed spinning.

The solidification rate and the stretching method can be appropriately set according to the purpose of the refractory fiber or carbon fiber.

The coagulation bath may contain so-called coagulation promoting components in addition to solvents such as dimethyl sulfoxide, dimethylformamide, and dimethyl acetamide. As the coagulation promoting component, it may be preferable to have a solvent and usability used in a spinning stock solution without dissolving the polyacrylonitrile-based polymer. Examples of water include water.

The temperature of the coagulation bath and the amount of the coagulation facilitating component can be appropriately set depending on the purpose of the refractory fiber or carbon fiber as the target.

After the spun multifilament is discharged into a coagulation bath to coagulate, the precursor fiber for carbon fiber can be obtained through washing, stretching, emulsifying (oiling), and dry densification. At this time, after solidifying the multi-filament may be subjected to a hydrothermal stretching step of the primary stretching in a hydrothermal stretching machine containing a hot water of 70 ~ 100 ℃ after washing through water washing process, or immediately performing the hydrothermal stretching process without washing with water Also good. In addition, in order to produce a strong carbon fiber precursor fiber may be carried out multi-stage stretching at low magnification, or high magnification stretching with hot steam.

That is, the present invention is characterized in that the secondary stretching at 110 ~ 130 ℃ temperature using a conventional steam stretching machine used for stretching the polyacrylonitrile multifilament.

In this manner, after the secondary stretching in the steam stretching machine is completed, it is possible to impart an oil agent to the multifilament to prevent adhesion between short fibers, and as an example of the oil agent, it is preferable to impart an oil agent such as silicon. It is preferable that such silicone emulsion is modified silicone, and it may be preferable to contain network modified silicone having high heat resistance.

Elongation in the hydrothermal stretching process is 2.0 to 5 times, elongation in the steam stretching process is preferably 1.2 to 3.0 times.

Finally, by winding the composite precursor multi-filament, it is possible to finish the production of the precursor fiber for carbon fiber, the winding speed in the winding process is preferably 4.0 to 15 times the spinning speed in the spinning process.

It is preferable that the short fiber fineness of the precursor fiber for carbon fiber obtained in this way is 0.01-3.0 dtex, More preferably, it is 0.05-2.2 dtex, More preferably, it is 0.8-2.0 dtex. If the short fiber fineness is too small, the process stability of the spinning process and the carbon fiber firing process may be lowered due to the occurrence of thread breakage due to contact with the roller or the guide. On the other hand, when the short fiber fineness is too large, the structural difference between the cross sections and the inner and outer layers in each short fiber after flame-proofing becomes large, and the processability fall in the subsequent carbonization process and the tensile strength and tensile elastic modulus of the carbon fiber obtained may fall. That is, outside the above range, the firing efficiency may be drastically lowered. The short fiber fineness (dtex) in this invention is the weight (g) per 10,000 m of short fibers.

The carbon fiber manufacturing method of the present invention heat-treated at a temperature of 180-220 ° C. while drawing a composite precursor fiber prepared by the above-described manufacturing method as a precursor fiber and stretching at a rate of -10 to -0.1% or 0.1 to 5%. A preliminary flameproofing process for converting to a preliminary flameproofing fiber; Flameproofing step of converting the preliminary flameproof fiber to a flameproof fiber by heat treatment at a temperature of 200 ~ 300 ℃ while stretching at an elongation of -5 ~ 5%; A preliminary carbonization step of preliminary carbonization at a temperature of 300 to 800 ° C. under an inert atmosphere; And a carbonization treatment step of carbonizing at a temperature of 1000 to 3000 ° C. under an inert atmosphere.

Preferably, the precursor fiber has a water content of 20 to 50%, and the carbon fiber manufactured through the preliminary flameproofing process, the flameproofing process, the preliminary carbonization treatment, and the carbonization treatment may undergo the processes. It is preferred to be stretched from -10 to 10% relative to the precursor fiber, and more preferably from 0.1 to 10%.

Example 1.

Polyacrylonitrile-based polymer solution was prepared using DMSO solution polymerization. DMSO: AN was prepared by mixing in a batch reactor by weight, and 0.1 wt% of AIBN (2,2'-Azobisisobutyronitrile) was added as an initiator and polymerized at 65 ° C. for 20 hours. After 20hr of reaction, ammonia water was added to terminate the reaction, and unreacted AN and ammonia water were removed under 20torr vacuum to prepare a solution polymer. In this case, the solid content in the solution polymer was 18% by weight, and the viscosity was 600Poise at 45 ° C.

0.1 wt% of ash content of purified hardwood lignin was added to the solution polymer at 10 wt% relative to the total solid content, and stirred at 60 ° C. for 5 hours to completely dissolve and then vacuum degassed to prepare a spinning stock solution.

In order to maintain the total solids content of 18% by weight in the stock solution, DMSO was added compared to the input of purified lignin.

The prepared spinning stock solution was wet-spun at a spinning temperature of 60 ° C. using a diameter of 0.09 mm and 3,000 wet spinning caps, and after passing through the washing process, three times with primary 100 ° C. hot drawing and secondly extending 130 ° C. steam. Stretched twice, and dried at 180 ℃ to prepare a composite precursor.

At this time, the spinning coagulation solution was an aqueous solution of 20% by weight of DMSO, the temperature was maintained at 60 ℃.

The composite precursor was carbonized at 1200 ° C. after preliminary carbonization at 500 ° C. in a nitrogen gas inert atmosphere through a flameproofing process at 250 ° C. to produce carbon fibers.

Example 2.

The carbon fiber was manufactured by repeating the same procedure as in Example 1 except that the purified lignin content was increased by 30% by weight relative to the total solid content.

Example 3.

The carbon fiber was manufactured by repeating the same procedure as in Example 1 except that the purified lignin content was increased by 50% by weight relative to the total solid content.

Example 4.

The carbon fiber was manufactured by repeating the same procedure as in Example 1 except that the purified lignin content was increased by 60% by weight relative to the total solid content.

Comparative Example 1

Purified lignin content is 0% by weight relative to the total solid content, and the same procedure as in Example 1 was repeated except that the polyacrylonitrile solution polymer was spun using as it was to produce a carbon fiber.

The physical properties of the spinning stock solution and the filament yarn prepared according to Examples 1 to 4 and Comparative Example 1 were evaluated in the following manner.

(a) strength (g / d)

After the test piece was allowed to stand at 25 ° C. RH65% for 24 hours, the prepared test piece was measured according to the KSK 0412 standard at a sample length of 250 mm and a tensile speed of 300 m / min using an Instron low speed extension type tensile tester.

(b) radiation stability

Radiation stability was determined according to the criteria of Table 1 below by observing the number of trimmings per 3000 spinning nozzles of the used spinneret when winding for 10 hours at a given spinning condition towing speed of 100 mpm.

Radio Stability Rating S A B F Thread Trimming Count (X) 0 0 <X ≤ 2 2 <X ≤ 5 5 <X

(c) Carbon fiber yield (%)

Carbon fiber yield is a value expressed as a percentage of the weight of the carbon fiber relative to the weight of the precursor input, the higher the carbon fiber yield, the lower the production cost is advantageous for the production of low-cost carbon fiber.

Carbon fiber yield (%) = carbon fiber production weight / precursor input weight x 100

Yarn properties measured according to the above method are summarized in Table 2 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Lignin: PAN (wt%) 10:90 30:70 50:50 60:40 0: 100 Radiation stability S A B F (bad radiation) S Carbon Fiber Fineness (De) 1.0 1.1 1.1 - 1.0 Carbon fiber strength (g / d) 15 10 7 - 17 Carbon fiber yield (%) 48 50 51 - 47

As shown in Table 2, the carbon fiber prepared by adding the lignin of the present invention is excellent in carbon fiber yield compared to the carbon island fiber of Comparative Example 1 by polyacrylonitrile alone, and is inexpensive using low-cost lignin. It can be seen that the competitiveness is excellent.

Glass fiber replacement reinforcing fiber used in the automotive industry can be used if the strength is more than 7g / d is enough to use for low-cost general purpose carbon fiber using a low-cost precursor.

Claims

A spinning solution manufacturing step of preparing a spinning solution by dissolving a polyacrylonitrile-based polymer and lignin in a solvent;
A spinning process of spinning a spinning solution containing the polyacrylonitrile-based polymer and lignin into a coagulation bath through a spinneret as a composite precursor multifilament;
A hydrothermal stretching step of primary stretching the composite precursor multifilament in a hydrothermal stretching machine including hot water at 70 to 100 ° C;
A steam stretching process of second stretching the composite precursor multifilament in a steam stretching machine at 110 to 130 ° C .; And
Method for producing a composite precursor multi-filament for carbon fiber comprising the winding step of winding the composite precursor multi-filament.

The method of claim 1, wherein the content ratio of the polyacrylonitrile-based polymer and lignin in the spinning solution manufacturing process is 90 to 50: 10 to 50 weight ratio.

The method of claim 1, wherein the lignin in the spinning manufacturing process has a ash content of 0.1 wt% or less.

The method according to claim 1, wherein the winding speed in the winding process is 8.0 to 15 times the spinning speed in the spinning process.

The method of claim 1, wherein the elongation is 3 to 5 times in the hydrothermal stretching process and the elongation is 1.2 to 3.0 times in the steam stretching process.

The method of claim 1, wherein the composite precursor multifilament to be produced finally has a water content of 20 to 50%.

Using the composite precursor multi-filament for carbon fiber prepared by any one of claims 1 to 6 as a precursor fiber,
A preliminary flameproofing step of converting the precursor fiber to a preliminary flameproof fiber by heat-treating at a temperature of 180-220 ° C. while stretching at a ratio of -10 to -0.1% or 0.1 to 5%;
Flameproofing step of converting the preliminary flameproof fiber to a flameproof fiber by heat treatment at a temperature of 200 ~ 300 ℃ while stretching at an elongation of -5 ~ 5%;
A preliminary carbonization step of preliminary carbonization at a temperature of 300 to 800 ° C. under an inert atmosphere; And a carbonization treatment step of carbonizing at a temperature of 1000 to 3000 ° C. under an inert atmosphere.

The method according to claim 7, wherein the carbon fiber produced through the preliminary flameproofing process, the flameproofing process, the preliminary carbonization treatment and the carbonization treatment is -10 to 10% compared to the precursor fiber during the processes Method for producing a carbon fiber, characterized in that the stretching.

The method according to claim 8, wherein the carbon fiber produced through the preliminary flameproofing process, the flameproofing process, the preliminary carbonization treatment and the carbonization treatment is drawn 0.1 to 10% compared to the precursor fiber during the processes Method for producing a carbon fiber, characterized in that.