JP2008297674A - Acrylic fiber for producing carbon fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide acrylic fibers for producing carbon fibers capable of preventing agglutination between mutual flameproofed fibers in a flameproofing step, having good bundling properties of the flameproofed fibers during running and further preventing formation of pollutants in a baking furnace in a carbonizing step when the carbon fibers are produced from the acrylic fibers. <P>SOLUTION: The acrylic fibers for producing the carbon fibers are obtained by applying moisture in an amount of 20-60 mass% based on the mass of the acrylic fibers having 5-20 μm fiber diameter. Furthermore, based on the acrylic fibers, a calcium component (A) within the range of 5-50 mass ppm, a sodium component (B) within the range of 0-50 mass ppm, a magnesium component (C) within the range of 0-50 mass ppm, the (A)+(B)+(C) within the range of 5-100 mass ppm and an aminosilicone within the range of 0.02-2.0 mass% are applied. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to acrylonitrile fibers (acrylic fibers) for producing carbon fibers. More specifically, the present invention focuses on fibers while preventing fusion (sticking) between the flame-resistant fibers in the flame-proofing process. In the carbonization process, the present invention is for carbon fiber production with less generation of contaminants in the firing furnace. Related to acrylic fiber.

  Conventionally, it has been widely known and industrially implemented that high-performance carbon fibers can be obtained by using acrylic fibers for producing carbon fibers and undergoing flameproofing treatment and carbonization treatment.

In particular, in recent years, the use of carbon fibers has expanded from sports / leisure products to aerospace, particularly to primary structural materials for aircraft. In addition, by utilizing the high specific strength and specific elasticity characteristics of carbon fiber to reduce the weight of the product, energy saving is achieved, and various industries pay attention to and research to contribute to the reduction of CO ₂ emissions. Yes. Accordingly, there is a demand for high-quality carbon fibers with high performance, low cost, and excellent handling properties. In the production of such high-performance carbon fibers, the characteristics of the acrylic fiber as the raw fiber directly affect the performance of the target carbon fiber. Therefore, it is desired to develop an acrylic fiber for carbon fiber that has high performance, low cost, and improved handling.

  In general, when carbon fibers are produced from acrylic fibers, a so-called flameproofing treatment is usually carried out in an oxidizing gas atmosphere at 200 to 300 ° C., and then carbonization treatment or graphitization treatment in an inert gas atmosphere at 350 ° C. or higher. I do. In this case, during the flameproofing treatment at 200 to 300 ° C., the single fibers constituting the strands (fiber bundles composed of hundreds to tens of thousands of single fibers) are likely to stick to each other, and the production of this can be prevented. Top is important.

  For this reason, methods for applying various silicone oils (treatment agents) (see, for example, Patent Documents 1 and 2) have been proposed, and in particular, methods for applying aminosilicone oils are well known. However, when aminosilicone-based oil is used, it is effective in preventing the occurrence of sticking at the time of flame resistance, but in the carbonization step after the flame resistance step, silicon oxide, silicon nitride, etc. due to decomposition of the treatment agent in the firing furnace Pollutants are generated and deposited. For this reason, it is necessary to frequently clean the inside of the firing furnace, which significantly reduces productivity.

In order to solve the above problem, conventionally, the use of a treatment agent containing no silicone as a lubricant has been proposed. For example, as a lubricant,
(1) A mixture containing a fatty acid ester of an alkylene oxide adduct of bisphenol A and an alkylene oxide adduct of an amide compound (see, for example, Patent Document 3),
(2) Contains a mixture of a compound having an amide group at the terminal obtained by reacting a condensate of a polyol having a dibasic acid and an oxyalkylene unit with an aliphatic alkanolamide, and an alkylene oxide adduct of the amide compound. Things (for example, see Patent Document 4)
There is. However, these treatment agents do not generate firing furnace contaminants in the carbonization step, but have a drawback in that the fusion between the flameproof fibers cannot be sufficiently prevented in the flame resistance step before the carbonization step.
Japanese Patent Publication No. 52-24136 (Claims) JP-A-61-167024 (page 3, upper left column, line 9 to upper right column, line 6) JP-A-9-78340 (Claims) JP-A-9-78341 (Claims)

  As a result of repeated examinations to solve the above problems, the present inventors have adhered to the acrylic fiber, by optimizing the amount of water, the amount of calcium component, the amount of sodium component, the amount of magnesium component, the amount of aminosilicone, The inventors have found that it is possible to prevent sticking and improve convergence in the flameproofing process, prevent the generation of contaminants in the carbonization furnace, and delay the blockage of the carbonization furnace.

  The problem to be solved by the present invention is a problem with conventional treatment agents, that is, when carbon fiber is produced from acrylic fiber, the problem that the flame resistant fibers are fused together in the flame resistance process, An object of the present invention is to provide an acrylic fiber for producing carbon fibers, which can solve both of the problems of poor convergence and, at the same time, can sufficiently solve the problem of generation of contaminants in the firing furnace in the carbonization step.

  The present invention for achieving the above object is as follows.

[1] To an acrylic fiber strand in which a plurality of acrylic fibers having a fiber diameter of 5 to 20 μm are bundled, the following components (1) to (5) [provided that the component (A) + ( B) + (C) total is 5-100 ppm by mass]
(1) 20-60% by weight of water,
(2) 5-50 mass ppm with calcium component (A) as calcium element,
(3) 0-50 mass ppm of sodium component (B) as sodium element,
(4) 0-50 mass ppm with magnesium component (C) as magnesium element,
(5) 0.02-2.0% by mass of aminosilicone,
Acrylic fiber for carbon fiber production made to adhere.

  [2] The acrylic fiber for producing carbon fiber according to [1], wherein the acrylic fiber strand is a bundle of 1000 to 50000 acrylic fibers.

  Since the acrylic fiber for producing carbon fibers of the present invention has 20 to 60% by mass of water attached to the mass of the acrylic fiber having a fiber diameter of 5 to 20 μm, it improves the fiber convergence until the flameproofing step. be able to. As a result, the cutting of the fiber and the winding of the fiber around the roller before the flameproofing process and when passing through the flameproofing process are reduced, the running stability is improved, and the cost is reduced by improving the productivity.

  And with respect to the acrylic fiber, the calcium component (A) is 5 to 50 mass ppm and / or the sodium component (B) is 50 mass ppm or less and / or the magnesium component (C) is 50 mass ppm or less, (A ) + (B) + (C) is adhered in the range of 5 to 100 mass ppm, so that sufficient fiber convergence is improved and sticking is prevented.

  The acrylic fiber to which the moisture, calcium component and the like are attached has further attached aminosilicone in an amount of 0.02 to 2.0% by mass with respect to the mass of the acrylic fiber, and does not attach moisture, calcium component and the like. It is also possible to reduce the occurrence of contaminants in the firing furnace in the carbonization step, which becomes a problem when only aminosilicone is adhered to the substrate.

  Hereinafter, the present invention will be described in detail.

  A feature of the present invention is that moisture, calcium component, sodium component, magnesium component, and aminosilicone are adhered to the acrylic fiber strand in which the acrylic fibers are bundled in a predetermined range. In the present invention, the acrylic fiber is a fiber produced by spinning a acrylonitrile homopolymer or a copolymer obtained by copolymerizing a small amount of a comonomer. As the comonomer, a copolymer obtained by copolymerizing 0.1 to 9.0% by mass of generally known acrylic acid, methacrylic acid, itaconic acid, and salts thereof is preferable.

  The acrylic fiber for carbon fiber production according to the present invention has moisture, calcium component, sodium component, and magnesium component attached thereto, so that the moisture acts as a sizing agent until the flameproofing process, and the acrylic fiber for carbon fiber production is a roller. Reduce the damage caused by contact with etc. In the flameproofing furnace, the water is not immediately evaporated, but the remaining calcium, sodium and / or magnesium components are scattered on the surface of the fiber, and appropriate fiber convergence and anti-sticking effect are exhibited.

  The moisture to be attached to the mass of the acrylic fiber is 20 to 60% by mass, preferably 23 to 55% by mass. When the moisture is less than 20% by mass, a sufficient focusing effect cannot be obtained, and damage due to contact with a roller or the like up to the flameproofing process cannot be sufficiently prevented. When the water content exceeds 60% by mass, sufficient convergence is obtained, but the strength of the carbon fiber is lowered.

  In the acrylic fiber for producing carbon fiber of the present invention, the calcium component (A) is 5 to 50 ppm by mass, and / or the sodium component (B) is 50 ppm by mass or less, and / or the magnesium component (C) is 50 masses. In the range of ppm or less, it adheres to the acrylic fiber.

  When the adhesion amount of the calcium component (A) is less than 5 ppm by mass, the amount scattered on the fiber surface is too small, so that sufficient focusing effect and anti-sticking effect cannot be obtained. On the other hand, when the adhesion amount of the calcium component (A), the sodium component (B), or the magnesium component (C) exceeds 50 mass ppm, sufficient convergence can be obtained, but the strength of the carbon fiber is lowered.

  The component to be adhered may be only one component, a combination of two components, or all three components among the calcium component (A), sodium component (B), and magnesium component (C). Moreover, in this invention, (A) + (B) + (C) is 5-100 mass ppm, Preferably it is the range of 10-60 mass ppm. When (A) + (B) + (C) is less than 5 ppm by mass, the amount of each component scattered on the fiber surface is too small, and sufficient focusing effect and anti-sticking effect cannot be obtained. On the other hand, if it exceeds 100 ppm by mass, sufficient convergence can be obtained, but the strength of the carbon fiber is lowered.

  In general, the calcium component in the acrylic fiber produced by a usual spinning method is 1 to 4 ppm by mass, the sodium component is 1 to 2 ppm by mass, and the magnesium component is 1 to 2 ppm by mass.

  The acrylic fiber for producing carbon fiber of the present invention is formed by attaching aminosilicone. The adhesion amount is 0.02 to 2.0 mass%, preferably 0.15 to 1.0 mass%, based on the mass of the acrylic fiber. As this amino silicone, those widely known as sizing agents (treatment agents) for acrylic fibers for producing carbon fibers are preferable. In particular, those represented by the following structural formula (general formula 1) have a high anti-sticking effect during flame resistance.

m and n are each a number of 1 to 100,000, m + n is a number of 10 or more, and R ₁ and R ₂ are the same or different alkylene groups or arylene groups having 1 to 10 carbon atoms.

  When the amount of aminosilicone adhered to the fiber is less than 0.02 parts by mass, the anti-sticking and focusing action in the flameproofing process is insufficient. On the other hand, if the adhesion amount exceeds 2.0 parts by mass, the carbonization furnace is quickly closed, and the inside of the carbonization furnace needs to be frequently cleaned, resulting in decreased productivity.

  When aminosilicone is attached to the acrylic fiber of the present invention, the viscosity of aminosilicone at 25 ° C. is preferably 500 to 5000 cSt (centistokes). In particular, it is preferably 1000 to 3000 centistokes. When the viscosity is less than 500 centistokes, the heat resistance is low and the particles are scattered in a flameproofing furnace, so that fusion between single yarns may not be prevented. On the other hand, when the viscosity exceeds 5000 centistokes, it is difficult to disperse in water, making it difficult to produce a treatment agent in the form of an emulsion, which will be described later, or finding a solvent with excellent solubility. It becomes difficult to uniformly apply the treatment agent to the surface of the fiber single yarn.

  In addition, since the aminosilicone component is water repellent, when the acrylic fiber is subjected to steam stretching, inconveniences such as non-uniformity of the moisture content of the fiber and non-uniform stretching treatment are likely to occur. For this reason, you may add a hygroscopic agent. Examples of the hygroscopic agent include dialkyl sulphosuccinate, polyoxyethylene (POE) alkyl ether and alkylamine oxide. The mixing ratio of the hygroscopic agent is preferably 10 to 60% by mass, more preferably 30 to 50% by mass based on the mass of the aminosilicone.

  The acrylic fiber strand to which water, calcium component, sodium component, magnesium component and aminosilicone are attached is preferably a bundle of 1000 to 50000 acrylic fibers.

  When applying the treatment agent to acrylic fibers, the wet-spun gel acrylic fiber or spinning solution is once discharged into the gas, then introduced into the coagulation bath, and the treatment agent is applied to the gel acrylic fiber stretched in the bath. Let me. Thereafter, drying and stretching are performed to obtain a carbon fiber precursor fiber. Examples of the usual treatment agent application method include a method of immersing the gel fiber in an emulsion of the treatment agent.

  As a method for producing a carbon fiber using the acrylic fiber of the present invention, a generally adopted method can be adopted. That is, after flameproofing at 200 to 300 ° C. in air, carbonizing at 300 to 2000 ° C. in an inert gas, and after performing surface treatment as necessary, a sizing agent is applied to obtain the carbon fiber. The obtained carbon fiber exhibits good physical properties and good handleability, and can be manufactured to satisfy the object of the present invention.

  Hereinafter, the present invention will be specifically described by way of examples. Acrylic fibers for producing carbon fibers, flameproofed fibers, and carbon fibers were produced under the conditions of the following Examples and Comparative Examples. In addition, various physical property values of acrylic fiber for carbon fiber production, flame-resistant fiber and carbon fiber, adhesion treatment agent amount in examples, bundling property of flame-resistant yarn, Si compound generation amount in carbonization process are as follows: It measured by the method of.

(1) Aminosilicone adhesion amount After extracting the treating agent from the acrylonitrile fiber for carbon fiber production with a mixed solution of ethanol and benzene, the mixed solution was distilled off and the obtained solid content was weighed.

(2) Calcium, sodium, and magnesium deposits Dry acrylonitrile fiber for carbon fiber production is extracted with distilled water while applying ultrasonic vibration, and the extracted components are quantified by IPC mass spectrometry (JIS K0102). did.

(3) Convergence of flame resistant yarn After making acrylonitrile fiber strands (12,000 single fibers) for carbon fiber production flame resistant at 250 ° C. in air, the strands are cut into 10 cm, and the strands are opened by hand. I was allowed to judge from the tactile sensation at that time. Evaluation of convergence is as follows: X: No convergence, easy opening △: Slight convergence (between × and ○)
◯: Judgment was made in a state in which the fibers converge and do not open unless force is applied.

(4) Strength of carbon fiber The strength of the epoxy resin-impregnated strand was measured according to JIS R-7601, and the average value of the number of measurements was four.

(5) Number of sticking Various filament strands, that is, flame-resistant fiber strands or carbon fiber strands, are cut to a length of 3 mm, put into a 100 ml beaker containing 10 ml of acetone, and subjected to ultrasonic vibration for 10 seconds or more. By observing at a magnification of 20 times, the number of fusion points was counted to determine the number of sticking.

(6) Si compound generation amount in the carbonization furnace The Si compound generated in the carbonization furnace was collected, the amount of Si compound generated per ton of acrylic fiber was calculated, and this was used as the generation amount.

[Examples 1 and 3 and Comparative Example 2]
97% by mass of acrylonitrile and 3% by mass of methyl acrylate were copolymerized to obtain polyacrylonitrile having an average molecular weight of 78,000. This polyacrylonitrile was dissolved in a 60% by mass zinc chloride aqueous solution to prepare a spinning dope having a polyacrylonitrile concentration of 8% by mass. This spinning dope was discharged into a zinc chloride aqueous solution at 10 ° C. and 25% by mass using a nozzle having 12,000 holes to obtain a coagulated yarn. While washing the coagulated yarn in warm water at 15 to 95 ° C., a total of 3.2 times of multi-stage drawing was performed to obtain a water-swollen acrylic fiber strand having a moisture content of 170 mass%.

  A treatment bath was prepared by mixing an aqueous solution of 4 g / L aliphatic phosphate ester and an emulsion of aminosilicone (viscosity at 25 ° C .: 1000 cSt, amino equivalent 2000) 2 g / L. The water-swelled acrylic fiber strand described above was immersed in this treatment agent bath and applied by a dip-nip method.

  Subsequently, it dried and densified until the moisture content became 1 mass% or less using the 70-150 degreeC suction drum dryer. Then, after passing through a hot water bath at 80 ° C., the film was redrawn 4.5 times in saturated steam of 0.07 MPa, transferred into a can, 1 dtex (0.9 denier), 12,000 acrylic fiber strands Got. The calcium in the acrylic fiber strand was 2 mass ppm, sodium was 1 mass ppm, and magnesium was 1 mass ppm.

  Next, calcium, sodium, and magnesium (manufactured by Kanto Chemical Co., Inc.) are dissolved in distilled water to prepare treated water, and acrylic fiber is passed through the treated water by a dip-nip method to produce carbon fiber acrylic fiber. Got. Table 1 shows the analysis results of the amounts of calcium, sodium, and magnesium, and the water content. Moreover, the aminosilicone adhesion amount of the obtained acrylic fiber was all 0.15 mass parts with respect to 100 mass parts of acrylic fibers.

  Thereafter, this acrylic fiber was subjected to a flameproofing treatment continuously for 40 minutes in a hot air circulation type flameproofing furnace having a temperature gradient within a range of 240 to 270 ° C. by a conventional method. Subsequently, it processed in the carbonization furnace which has a temperature gradient of 300-1300 degreeC in nitrogen stream for 5 minutes, and was set as carbon fiber. The obtained results are shown in Tables 1 and 2.

[Example 2]
A treatment bath was prepared by mixing an aqueous solution of 4 g / L aliphatic phosphate and an emulsion of aminosilicone (viscosity at 25 ° C .: 1000 cSt, amino equivalent 2000) 4 g / L. The water-swelled acrylic fiber strands prepared in Examples 1 and 3 and Comparative Example 2 were immersed in this treatment agent bath and applied by a dip-nip method.

  Subsequently, it dried and densified until the moisture content became 1 mass% or less using the 70-150 degreeC suction drum dryer. Then, after passing through a hot water bath at 80 ° C., the film was redrawn 4.5 times in saturated steam of 0.07 MPa, transferred into a can, 1 dtex (0.9 denier), 12,000 acrylic fiber strands Got. The calcium in the acrylic fiber strand was 2 mass ppm, sodium was 1 mass ppm, and magnesium was 1 mass ppm.

  Next, calcium, sodium, and magnesium (manufactured by Kanto Chemical Co., Inc.) are dissolved in distilled water to prepare treated water, and acrylic fiber is passed through the treated water by a dip-nip method to produce carbon fiber acrylic fiber. Got. Table 1 shows the analysis results of the amounts of calcium, sodium, and magnesium, and the water content. Moreover, the aminosilicone adhesion amount of the obtained acrylic fiber was all 1.15 mass parts with respect to 100 mass parts of acrylic fibers.

  Thereafter, this acrylic fiber was subjected to a flameproofing treatment continuously for 40 minutes in a hot air circulation type flameproofing furnace having a temperature gradient within a range of 240 to 270 ° C. by a conventional method. Subsequently, it processed in the carbonization furnace which has a temperature gradient of 300-1300 degreeC in nitrogen stream for 5 minutes, and was set as carbon fiber. The obtained results are shown in Table 1.

[Comparative Example 1]
A treatment bath was prepared by mixing an aqueous solution of 4 g / L aliphatic phosphate and an emulsion of 1 g / L aminosilicone (viscosity at 25 ° C .: 1000 cSt, amino equivalent 2000). The water-swelled acrylic fiber strands prepared in Examples 1 and 3 and Comparative Example 2 were immersed in this treatment agent bath and applied by a dip-nip method.

  Subsequently, it dried and densified until the moisture content became 1 mass% or less using the 70-150 degreeC suction drum dryer. Then, after passing through a hot water bath at 80 ° C., the film was redrawn 4.5 times in saturated steam of 0.07 MPa, transferred into a can, 1 dtex (0.9 denier), 12,000 acrylic fiber strands Got. The calcium in the acrylic fiber strand is 2 ppm by mass, sodium is 1 ppm by mass, and magnesium is 1 ppm by mass. The aminosilicone adhesion amount of the acrylic fiber is 0.08 parts by mass with respect to 100 parts by mass of the acrylic fiber. It was.

  Thereafter, this acrylic fiber was subjected to a flameproofing treatment continuously for 40 minutes in a hot air circulation type flameproofing furnace having a temperature gradient within a range of 240 to 270 ° C. by a conventional method. Subsequently, it processed in the carbonization furnace which has a temperature gradient of 300-1300 degreeC in nitrogen stream for 5 minutes, and was set as carbon fiber. The obtained results are shown in Table 2.

[Comparative Example 3]
A treatment bath was prepared by mixing an aqueous solution of 4 g / L aliphatic phosphate ester and an emulsion of 8 g / L aminosilicone (viscosity at 25 ° C .: 1000 cSt, amino equivalent 2000). The water-swelled acrylic fiber strands prepared in Examples 1 and 3 and Comparative Example 2 were immersed in this treatment agent bath and applied by a dip-nip method.

  Subsequently, it dried and densified until the moisture content became 1 mass% or less using the 70-150 degreeC suction drum dryer. Then, after passing through a hot water bath at 80 ° C., the film was redrawn 4.5 times in saturated steam of 0.07 MPa, transferred into a can, 1 dtex (0.9 denier), 12,000 acrylic fiber strands Got. The calcium in the acrylic fiber strand is 2 ppm by mass, sodium is 1 ppm by mass, and magnesium is 1 ppm by mass. The aminosilicone adhesion amount of the acrylic fiber is 0.60 parts by mass with respect to 100 parts by mass of the acrylic fiber. It was.

  Thereafter, this acrylic fiber was subjected to a flameproofing treatment continuously for 40 minutes in a hot air circulation type flameproofing furnace having a temperature gradient within a range of 240 to 270 ° C. by a conventional method. Subsequently, it processed in the carbonization furnace which has a temperature gradient of 300-1300 degreeC in nitrogen stream for 5 minutes, and was set as carbon fiber. The obtained results are shown in Table 2.

[Comparative Example 4]
The water-swelled acrylic fiber strands prepared in Examples 1 and 3 and Comparative Example 2 described above were immersed in a treatment bath having an aliphatic phosphate ester concentration of 8 g / L and applied by a dip-nip method.

  Subsequently, it dried and densified until the moisture content became 1 mass% or less using the 70-150 degreeC suction drum dryer. Then, after passing through a hot water bath at 80 ° C., the film was redrawn 4.5 times in saturated steam of 0.07 MPa, transferred into a can, 1 dtex (0.9 denier), 12,000 acrylic fiber strands Got. The calcium in the acrylic fiber strand was 2 mass ppm, sodium was 1 mass ppm, and magnesium was 1 mass ppm.

  Next, calcium, sodium, and magnesium (manufactured by Kanto Chemical Co., Inc.) are dissolved in distilled water to prepare treated water, and acrylic fiber is passed through the treated water by a dip-nip method to produce carbon fiber acrylic fiber. Got. Table 2 shows the results of analysis of the amount of calcium, sodium, and magnesium adhered, and the amount of water. Moreover, the aminosilicone adhesion amount of the obtained acrylic fiber was all 0 mass parts with respect to 100 mass parts of acrylic fibers.

  Thereafter, this acrylic fiber was subjected to a flameproofing treatment continuously for 40 minutes in a hot air circulation type flameproofing furnace having a temperature gradient within a range of 240 to 270 ° C. by a conventional method. Subsequently, it processed in the carbonization furnace which has a temperature gradient of 300-1300 degreeC in nitrogen stream for 5 minutes, and was set as carbon fiber. The obtained results are shown in Table 2.

Claims (2)

To an acrylic fiber strand in which a plurality of acrylic fibers having a fiber diameter of 5 to 20 μm are bundled, the following components (1) to (5) with respect to the mass of the acrylic fiber strand [where component (A) + (B) + (C) total is 5 to 100 ppm by mass]
(1) 20-60% by weight of water,
(2) 5-50 mass ppm with calcium component (A) as calcium element,
(3) 0-50 mass ppm of sodium component (B) as sodium element,
(4) 0-50 mass ppm with magnesium component (C) as magnesium element,
(5) 0.02-2.0% by mass of aminosilicone,
Acrylic fiber for carbon fiber production made to adhere. The acrylic fiber for producing carbon fibers according to claim 1, wherein the acrylic fiber strand is a bundle of 1000 to 50000 acrylic fibers.