JP2001172880A - Silicone oil agent for carbon fiber and method for producing carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone oil agent for carbon fiber suitable for the production of carbon fiber having excellent cost-performance and provide a method for producing a carbon fiber by using a silicone oil agent free from generation of baking unevenness in flame-resisting process to improve the baking processability and achieving the baking of carbon fiber with high filament density, high tensile force and high speed. SOLUTION: The silicone oil agent for carbon fiber satisfies the formulas; 0.03<=T<=0.4 and T=T30-T180 wherein T30 is the oscillation period (sec) of a rigid pendulum measured by free oscillation decay method at 30 deg.C; and T180 is the oscillation frequency (sec) after the heat-treatment at 180 deg.C for 10 min. The carbon fiber is produced by applying the silicone oil agent to a fiber wet with water, heat-treating at 150-200 deg.C to obtain an acrylic precursor for carbon fiber, subjecting the precursor to flame-resisting treatment in an oxidizing atmosphere at 200-300 deg.C, preparatorily carbonizing in an inert atmosphere at 300-800 deg.C and finally carbonizing in an inert atmosphere at 800-1,800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a carbon fiber excellent in cost performance and a method for producing the same, a silicone oil agent for carbon fiber suitable for producing the carbon fiber, an acrylic precursor, and a method for producing the same.

[0002]

2. Description of the Related Art Since carbon fibers have higher specific strength and specific elastic modulus than other reinforcing fibers, carbon fibers are industrially widely used as reinforcing fibers for composite materials by utilizing their excellent mechanical properties. I have. Its application range is expanding greatly to general industrial applications such as civil engineering and construction in addition to conventional sports and aerospace applications, and the market demand is not only for higher performance but also for lower cost. It is becoming tougher for higher performance.

[0003] The most widely used polyacrylonitrile-based carbon fibers are acrylic precursors of 200-4.
It is industrially manufactured through a flame-proofing step of converting into a flame-resistant fiber under an oxidizing atmosphere of 00 ° C. and a carbonizing step of carbonizing under an inert atmosphere of at least 1000 ° C. In these baking processes, there was a problem that fusion between the single fibers occurred, and the quality and quality of the obtained carbon fibers were reduced. To solve this problem, many techniques for applying a silicone oil having high heat resistance to an acrylic precursor have been proposed and widely applied industrially. For example, tokuho 3-401
No. 52 discloses that an oil agent in which a specific amino-modified silicone, epoxy-modified silicone, or alkylene oxide-modified silicone is mixed has a small weight loss upon heating in air and nitrogen and has a high anti-fusing effect. I have. However, the inventors of the present invention have examined that such a conventionally known silicone oil has a sufficient effect of preventing fusion of single fibers, but has a flameproofing effect due to interposition between single fibers. It has been clarified that the supply of oxygen essential for the reaction is hindered, and as a result, unevenness in the progress of the flame resistance reaction, that is, generation of so-called unevenness in firing is induced.
Such non-uniformity in firing causes yarn breakage and fluff in the subsequent carbonization step, and is a major obstacle to improving productivity. In order to produce high-performance carbon fiber with high productivity,
It is advantageous to fire a precursor having a smoother surface at a high yarn density and a high tension, but under such conditions, the adverse effect of the uneven firing becomes more remarkable, and the yarn density, the tension, and the processing speed are increased. At present, it is inevitable to reduce.

As a technique for suppressing firing unevenness, the present inventors have applied a technique of applying an acrylic precursor having a specific surface roughness (Japanese Patent Application Laid-Open No. 11-217732).
But it is advantageous for improving the strength of the obtained carbon fiber,
In the acrylic precursor having a smoother surface, the effect of suppressing the effect is not necessarily sufficient, which has become evident in subsequent studies, and in fact, a more effective means for suppressing uneven firing is required.

[0005]

DISCLOSURE OF THE INVENTION In view of the background of the prior art, the present invention provides a silicone oil agent for carbon fiber suitable for producing carbon fiber excellent in cost performance.
And a method for producing carbon fiber. That is, the use of a silicone oil agent that does not induce uneven firing in the flame-proofing step improves the firing processability, thereby achieving high yarn density, high tension, and high-speed firing.

[0006]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the silicone oil agent for carbon fiber of the present invention is:
The vibration period difference T of the pendulum measured by the free damping vibration method of the rigid pendulum satisfies the following expression.

0.03 ≦ T ≦ 0.4 T = T30−T180 T30: vibration cycle at 30 ° C. (second) T180: vibration cycle after heat treatment at 180 ° C. for 10 minutes (second) The production method comprises applying the silicone oil agent to the water-swollen yarn, and then applying 150 to 2
The acrylic precursor for carbon fiber obtained by heat treatment at a temperature of 00 ° C. is made flame-resistant in an oxidizing atmosphere of 200 to 300 ° C., and then pre-carbonized in an inert atmosphere of 300 to 800 ° C., and further 800 to 1800 ° C. In an inert atmosphere.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have solved the above problem,
The present inventors have found that there is a correlation between uneven firing during oxidization and curing behavior during heat treatment of a silicone oil agent applied in a yarn-making process, and arrived at the present invention. That is, by employing a silicone oil in which the oscillation period difference T of the pendulum measured by the method described later (hereinafter simply referred to as the oscillation period difference T) is controlled to a specific range, the firing unevenness due to flame resistance is reduced. It can be suppressed effectively.

Further, by oxidizing the acrylic precursor for producing carbon fiber having the silicone oil agent of the present invention on its surface, oxidized fiber with less firing unevenness can be obtained, and the occurrence of yarn breakage and fluff in the subsequent carbonization step can be suppressed. Becomes possible,
As a result, they have determined that it is possible to obtain a carbon fiber having higher yarn density, higher tension, higher speed, and excellent cost performance without lowering the productivity as compared with the conventional firing technique.

The silicone oil of the present invention has a vibration cycle difference T
Is preferably 0.03 to 0.4, and 0.05 to 0.3.
5, more preferably 0.10 to 0.30. If the ratio is out of the above range, it is difficult to obtain the effects of the present invention. That is, they have the following relationship.

0.03 ≦ T ≦ 0.4 T = T30−T180 T30: Vibration period at 30 ° C. (second) T180: Vibration period after heat treatment at 180 ° C. for 10 minutes (second) Rigid pendulum free damping vibration method The principle is, for example, coloring materials,
51 (1978), 403p, etc.
Unlike a general rheometer, it can measure viscoelastic behavior in an open system and in a thin film state. The vibration cycle measured by the measuring method corresponds to the degree of crosslinking of the silicone oil agent, and a smaller value indicates a higher degree of crosslinking. Therefore, the vibration cycle difference T
(= T30-T180) corresponds to the curing behavior at the time of heating, and indicates that the larger the value, the easier the curing, that is, the easier the crosslinking. The reason why the application of the silicone oil having the oscillation cycle controlled in the above range can suppress unevenness in firing due to flame resistance is not necessarily clear,
It is estimated as follows. The non-uniformity in sintering due to flame resistance is caused by the fact that the permeation of oxygen into the yarn bundle is hindered and a part that is not sufficiently supplied is generated. The silicone oil present between the single fibers is considered as one of the hindrance factors. That is,
The silicone oil penetrates between the single fibers and acts like a sealant. Generally, the silicone oil agent is applied just before the drying step in the spinning process and is subjected to a heat treatment. If an oily state having fluidity is maintained without cross-linking during the drying heat treatment, then it can be freely deformed in accordance with the space between the single fibers, so that there is a high possibility of thick deposits between the single fibers, resulting in a sealing effect. It is thought to increase. On the other hand, if the composition is quickly cured and the fluidity is suppressed to a low level, it is considered that deposition between the single fibers is prevented, the constraint between the single fibers is reduced, and uneven firing is unlikely to occur.
However, when the curing progresses significantly, the constraint between the fibers increases,
It is thought that uneven firing results.

Further, the silicone oil of the present invention preferably has high heat resistance from the viewpoint of preventing fusion in the firing step. As the heat resistance index, the heating residual ratio R measured by a method described below is preferably 40 to 90%,
It is more preferably from 50 to 85%, and still more preferably from 60 to 80%. If it is less than 40%, the effect of the present invention is hardly obtained, and the strength of the carbon fiber finally obtained by fusion may be reduced. If it exceeds 90%, the adhesive strength between the carbon fiber and the matrix when used as a composite material may decrease.

The silicone oil of the present invention preferably has a small amount of so-called gum-up, which is dropped onto a roller or a guide, especially a heating roller, from the viewpoint of the spinning process.

In the present invention, the silicone oil is an oil containing at least 0.1% by weight of silicone, and may be a silicone alone or a solution using an organic solvent or the like. From the viewpoint of application simplicity, an aqueous emulsion is preferred. When forming an aqueous emulsion, a suitable emulsifier can be added to the silicone, but from the viewpoint of satisfying the above-mentioned properties, the emulsifier is preferably not more than 40 parts by weight based on 100 parts by weight of the silicone. From the viewpoint of long-term stability, an antioxidant and the like can be added, but it is preferable to select one that does not inhibit the crosslinking reaction of silicone.

The silicone used in the silicone oil agent of the present invention is not particularly limited as long as the vibration period difference T satisfies the above range, but the following embodiment is preferably adopted.

The silicone used in the silicone oil agent of the present invention preferably has a basic structure of polydimethylsiloxane and is partially modified with a methyl group. As the modifying group, an amino group, an epoxy group, an alkylene oxide group, and the like are preferable, and those that cause a crosslinking reaction by heating are preferably used. Silicones having a plurality of modifying groups may be used, or silicones having different modifying groups may be mixed and used. From the viewpoint of uniformity imparting to the acrylic precursor, it is preferable to use amino-modified silicone, and from the viewpoint of heat resistance, it is more preferable to use amino-modified silicone and epoxy-modified silicone.

In the case of an aqueous emulsion, it is preferable to use an alkylene oxide-modified silicone from the viewpoint of emulsification stability. In this case, the viscosity at 25 ° C. is preferably 20 to 1000 cSt, and 50 to 1000 cSt.
800 cSt is more preferred, and 100 to 500 cSt is even more preferred. Further, the ratio is preferably 0.5 to 10 parts by weight, more preferably 1 to 7 parts by weight, and preferably 1.5 to 5 parts by weight based on 100 parts by weight of all silicone compounds. More preferably, 10
If the amount is more than 10 parts by weight, the cross-linking reaction of another silicone may be delayed, and it may be difficult to obtain the effects of the present invention, or the heat resistance may be reduced. If the amount is less than 0.5 part by weight, the effect of improving the emulsion stability may not be obtained remarkably.

When an amino-modified silicone is used, the modifying group may be a monoamine type or a polyamine type. The amino group is considered to be a starting point of the cross-linking reaction. The cross-linking reaction is promoted as the amount of modification increases, but the amount of gum-up may increase. Converted to 0.05-10% by weight
Is preferable, and 0.1 to 5% by weight is more preferable. Also,
The lower the viscosity of the amino-modified silicone at 25 ° C., the higher the reactivity and the cross-linking reaction is accelerated. However, from the viewpoint of heat resistance, the higher the better, the more preferable it is 500 to 100.
00 cSt is preferred, 700 to 7000 cSt is more preferred, and 1000 to 4000 cSt is even more preferred.

When an amino-modified silicone or an epoxy-modified silicone is used, the epoxy-modified group may be alicyclic or glycidyl, but is preferably an alicyclic from the viewpoint of long-term stability. Since the epoxy group causes a crosslinking reaction with the amino group, the amount of modification is preferably equal to the amount of modification of the amino group described above, and is preferably 0.05 to 10% by weight.
1-5% by weight is more preferred. Further, the viscosity of the epoxy-modified silicone at 25 ° C. is preferably higher from the viewpoint of heat resistance, preferably from 1,000 to 30,000 cSt, more preferably from 5,000 to 20,000 cSt, and
00-15000 cSt is more preferable. The ratio of amino-modified silicone and epoxy-modified silicone is
Although the crosslinking reaction is promoted as the amount of the amino-modified silicone increases, the heat resistance decreases.
The epoxy-modified silicone is 10 to 100 parts by weight.
80 parts by weight is preferable, 20 to 70 parts by weight is more preferable, and 30 to 60 parts by weight is further preferable.

Further, the method for producing carbon fiber of the present invention will be described.

In the method for producing carbon fiber of the present invention, the above-mentioned silicone oil is applied to a water-swelled yarn,
Acrylic precursor for carbon fiber obtained by heat treatment at a temperature of ~ 200 ° C is oxidized in an oxidizing atmosphere of 200-300 ° C, preliminarily carbonized in an inert atmosphere of 300-800 ° C, and further treated at a temperature of 800-1800 ° C. It is characterized by being carbonized in an inert atmosphere.

As components of the acrylic precursor used in the present invention, at least 95 mol% or more, more preferably 98% or more of acrylonitrile and 5 mol% or less, more preferably 2 mol% or less, of promoting flame resistance, And,
What copolymerized acrylonitrile and the flame-resistance-promoting component which has copolymerizability can be used conveniently.

As such a flame-resistance-promoting component, a copolymer comprising a vinyl group-containing compound (hereinafter referred to as a vinyl monomer) is preferably used. Specific examples of the vinyl monomer include acrylic acid, methacrylic acid, and itaconic acid, but are not limited thereto. In addition, a copolymer composed of an ammonium salt of acrylic acid, methacrylic acid, or itaconic acid partially or wholly neutralized with ammonia is more preferably used as a component for promoting flame resistance.

The stock solution for spinning can employ a conventionally known solution polymerization method, suspension polymerization method, emulsion polymerization method and the like. As the solvent used in the spinning solution, organic and inorganic conventionally known solvents can be used. It is particularly preferable to use an organic solvent, and specifically, dimethylsulfoxide, dimethylformamide, dimethylacetamide and the like are used, and dimethylsulfoxide is particularly preferably used.

As the spinning method, a dry-wet spinning method or a wet spinning method is preferably employed, but the former is more preferably used because a raw yarn having a smoother surface can be produced with high productivity.

The raw spinning solution is discharged directly or indirectly from the spinneret into a coagulation bath to obtain a coagulated yarn. The coagulation bath solution is preferably composed of a solvent used for the spinning solution and a coagulation accelerating component from the viewpoint of simplicity, and more preferably water is used as the coagulation accelerating component. The ratio of the spinning solvent and the coagulation accelerating component in the coagulation bath and the temperature of the coagulation bath liquid are appropriately selected and used in consideration of the denseness, surface smoothness, spinnability and the like of the obtained coagulated yarn.

The obtained coagulated yarn is preferably washed and stretched in one or more water baths controlled at a temperature of 20 to 98 ° C. The draw ratio can be appropriately set as long as yarn breakage and adhesion between the single fibers do not occur. However, in order to obtain an acrylic precursor having a smoother surface, it is preferably 5 times or less, more preferably 4 times or less. It is preferably 3 times or less. Further, from the viewpoint of improving the denseness of the obtained acrylic precursor, the maximum temperature of the stretching bath is preferably 50 ° C. or higher, more preferably 70 ° C. or higher.

It is preferable to apply the above-mentioned silicone oil to the water-swollen yarn after the washing and stretching.
The application method may be appropriately selected and used in consideration of uniform application to the inside of the yarn. Specifically, the yarn is immersed in an oil bath, sprayed and dripped on the traveling yarn. Such means are adopted.

The amount of the silicone oil applied is preferably 0.1 to 5% by weight, more preferably 0.3 to 3% by weight, more preferably 0.5 to 2% by weight, based on the dry weight of the fiber.
% By weight is more preferred. If the amount is less than 0.1% by weight, fusion between the single fibers may occur, and the tensile strength of the obtained carbon fiber may decrease. If it exceeds 5% by weight, the effects of the present invention may not be obtained.

The yarn to which the oil agent has been applied is preferably dried quickly. The method of drying is not particularly limited, but a method of directly contacting a plurality of heated rollers is preferably used. The higher the drying temperature, the faster the cross-linking reaction of the silicone oil agent is promoted, and it is preferable from the viewpoint of productivity. Therefore, the drying temperature can be set high within a range where fusion between the single fibers does not occur. Specifically, the temperature is preferably 150 ° C. or higher, more preferably 180 ° C. or higher. Usually, the upper limit of the drying temperature is about 200 ° C. The drying time is preferably a time sufficient for the swollen yarn to dry. Further, it is preferable that the yarn is brought into contact with the roller in a state where the yarn is widened as much as possible so that the heating state of the yarn is uniform.

The dried yarn is preferably post-drawn in steam under pressure or under dry heat, from the viewpoint of the denseness and productivity of the obtained acrylic precursor. The steam pressure or temperature during the post-stretching and the post-stretching ratio may be appropriately selected and used within a range in which yarn breakage and fluff do not occur.

The acrylic precursor used in the present invention is:
The surface is preferably smooth from the viewpoint of obtaining high-performance carbon fibers. The smoothness is determined by using a surface area ratio measured by a method described later as an index, and the surface area ratio is preferably 1.00 to 1.05, more preferably 1.00 to 1.02, and 1.00. ~ 1.01 is more preferred. The smoother it is, the more easily the application effect of the silicone oil agent of the present invention is exerted. If it exceeds 1.05, the effect of the present invention may be difficult to obtain.

The fineness of the single yarn of the acrylic precursor used in the present invention is preferably 0.1 to 2.0 dTex, more preferably 0.3 to 1.5 dTex, and more preferably 0.5 to 1.0 dTex. 2dTex is more preferred. The smaller the fineness is, the more advantageous in terms of tensile strength and elastic modulus of the obtained carbon fiber, but the productivity is reduced. Therefore, it is preferable to select the carbon fiber in consideration of the balance between performance and cost.

An acrylic precursor is manufactured by the above-mentioned preferred method, and by firing by the method described below, a carbon fiber excellent in cost performance can be manufactured.

The oxidization temperature is preferably 200 to 300 ° C.
It is preferred from the viewpoint of reducing the cost and enhancing the performance of the obtained carbon fiber that the yarn is made flame-resistant at a temperature lower by 10 to 20 ° C. than the temperature at which the yarn breaks due to the heat storage of the reaction heat. The degree of progress of flame resistance is preferably in the range of 70% to 90%, more preferably 74% to 86%, and more preferably 76% to 84%, using the flame shrinkage of the flame resistant yarn measured by a method described later as an index.
% Is more preferred. The oxidization time is preferably from 10 to 100 minutes, more preferably from 30 to 60 minutes, from the viewpoint of enhancing the productivity and the performance of the obtained carbon fiber. This oxidization time refers to the total time during which the yarn stays in the oxidization furnace. If this time is less than 30 minutes, the double structure of each single fiber becomes remarkable as a whole, and the effect of the present invention may not be obtained. The stretching ratio in the flame-proofing step is 0.90 to 1.0
5 is preferable, 0.91 to 1.02 is more preferable, and 0.9
2-1.00 is more preferable.

The temperature in the preliminary carbonization step is preferably 300 to 800 ° C. Further, the stretching ratio is preferably 0.98 to 1.10, more preferably 0.99 to 1.05.
More preferably, it is 00 to 1.02.

The temperature in the carbonization step is preferably 800 to 1800 ° C. The maximum temperature is appropriately selected and used depending on the required characteristics of the desired carbon fiber.
If the temperature is lower than 0 ° C., the tensile strength and the elastic modulus of the obtained carbon fiber may decrease. The draw ratio in the carbonization step may be appropriately selected according to the required characteristics of the desired carbon fiber within a range that does not cause deterioration such as fluff.

The obtained carbon fiber can be further improved in adhesive strength to a matrix when a composite material is formed by surface treatment. As the surface treatment method, a gas phase or a liquid phase treatment can be adopted, but in consideration of productivity and quality variation, an electrolytic treatment in the liquid phase treatment is preferably applied.

As the electrolytic solution used in the electrolytic treatment, acids such as sulfuric acid, nitric acid and hydrochloric acid, alkalis such as sodium hydroxide, potassium hydroxide and tetraethylammonium hydroxide or salts thereof can be used. An aqueous solution containing ions is preferred. For example, ammonium nitrate, ammonium sulfate, ammonium persulfate, ammonium chloride, ammonium bromide, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium hydrogen carbonate, ammonium carbonate, or a mixture thereof can be used.

The amount of electricity in the electrolytic treatment varies depending on the carbon fiber used. For example, a carbon fiber having a higher degree of carbonization requires a higher amount of electricity. As the surface treatment amount, the surface oxygen concentration O / C and the surface nitrogen concentration N / C of the carbon fiber measured by X-ray photoelectron spectroscopy (ESCA) are 0.05 or more and 0.40 or less, respectively. It is preferably in the range from 02 to 0.30.

By satisfying these conditions, the adhesion between the carbon fiber and the matrix is at an appropriate level,
Therefore, there is also the disadvantage that the adhesion is too strong, resulting in a very brittle fracture and the strength is reduced, or the disadvantage that the strength is strong but the adhesion is too low and non-longitudinal mechanical properties are not exhibited. Characteristics that have composite properties that are well balanced in the vertical and horizontal directions.

The obtained carbon fiber is further subjected to a sizing treatment as required. The sizing agent is preferably a sizing agent having good compatibility with the matrix,
Selected and used according to the matrix.

The measured values described above and the measured values in the examples described later were measured by the following methods. <Vibration cycle of silicone oil based on free damping vibration method of rigid pendulum> RPT-30 rigid pendulum type physical property tester manufactured by A & D Corporation based on the free damping vibration method of rigid pendulum.
The oscillation cycle is measured using 00. Length 5cm, width 2c
The thickness of the silicone oil to be used for the measurement is adjusted to a thickness of 20 to 30 μm on a 0.5 mm thick coated substrate made of galvanized steel sheet (STP-012 manufactured by A & D Corporation) in terms of a pure component. Apply over the entire surface. Immediately after application, set the tester and start measurement. After adjusting the temperature to 30 ° C in advance and setting the coating plate and the pendulum,
The temperature is raised to 180 ° C at a rate of ° C / min, and held at 180 ° C for 10 minutes. During that time, the period is continuously measured at intervals of 7 seconds. The following pendulum is used.

Edge used: Knife-shaped edge (RBE-160 manufactured by A & D Corporation) Pendulum weight / inertia ratio: 15 g / 640 g · cm (FRB-100 manufactured by A & D Corporation) <Surface ratio of acrylic precursor > Acrylic precursor to be used for measurement is fixed on a sample table, and an image of a three-dimensional surface shape is obtained under the following conditions using NanoScope III manufactured by Digital Instruments as an atomic force microscope.

Probe: SiN cantilever (Olympus Kogyo Kogyo Co., Ltd., spring constant 0.7 N / m) Measurement environment: At room temperature in the air Observation mode: Contact mode (constant force) Scanning speed: 0.2 to 0.5 Hz Scanning range : 2.4 μm × 2.4 μm About the obtained image, the software (Nano
Data processing is performed using ScopeIII version 4.22r2, first-order Flatten filter, Lowpass filter, and third-order Plane Fit filter), and the actual surface area and projected area are calculated. As for the projected area, the projected area on a secondary curved surface or the like approximated in consideration of the curvature of the fiber cross section is calculated and used. The surface area ratio is defined by the following equation.

Surface area ratio = actual surface area / projected area <Remaining rate of heating of silicone oil R> The remaining rate of heating was determined by heat-treating silicone oil in air at 240 ° C. for 60 minutes, and subsequently in nitrogen at 450 ° C. for 30 seconds. It refers to the residual rate after doing so. The measurement is performed according to the following procedure. When the silicone to be applied is an oil or emulsion or solution,
About 1 g of the emulsion or solution is collected in an aluminum container having a diameter of about 60 mm and a height of about 20 mm, and dried in an oven at 105 ° C. for 5 hours. The heat-resistant residual ratio is measured by a balance (TG).

Sample pan: aluminum diameter 5 mm, height 5 mm Sample amount: 15 to 20 mg Air heat treatment conditions: Air flow rate 30 ml / min, temperature rise rate 1
0 ° C / min, 240 ° C Heat treatment time: 60 minutes Atmosphere change: Change from air to nitrogen at 240 ° C and 5
Hold for 1 minute Heat treatment in nitrogen: Nitrogen flow rate 30 ml / min, temperature rise rate 10 ° C./min, 450 ° C. Heat treatment time: 30 seconds The total weight retention rate in this heat treatment is defined as a heating residual rate R. <Flame shrinkage retention rate of flameproofed yarn> A flameproofed yarn bundle is sampled about 40 cm, and marked with a non-combustible material such as a clip so as to have a test length of 20 cm. Next, fix one end and 3
A tension of 10 g per 300 dTex is applied, and the marked sample length is heated by a Bunsen burner flame. At this time, the height of the flame of the Bunsen burner was set to about 15 cm, the upper third of the flame was used, and the interval between marks was set to about 15 seconds / 2.
Heat while moving one and a half times at a speed of 0 cm. Thereafter, the length between marks is measured, and this is defined as Wb (mm). The flame shrinkage retention (%) is defined by the following equation.

Flame shrinkage retention (%) = (Wb / 200) × 100 <Stretchability in preliminary carbonization step>
Under a condition in which the temperature is raised to a maximum temperature of 650 ° C. at 0 ° C./min, a preliminary carbonization step is continuously passed to measure a critical draw ratio at which a yarn break occurs. <Strength and Elastic Modulus of Carbon Fiber> The strength of carbon fiber is determined by a method described in Japanese Industrial Standards (JIS) -R-7601 “Resin-impregnated strand test method”. However, the resin impregnated strand of the carbon fiber to be measured is "B"
AKELITE "ERL4221 (100 parts by weight) / 3
Carbon fiber was impregnated with boron fluoride monoethylamine (3 parts by weight) / acetone (4 parts by weight),
Cured in minutes. The number of strands to be measured is six, and the average value of each measurement result is defined as the strength and elastic modulus of the carbon fiber.

[0049]

The present invention will be described more specifically below with reference to examples. In addition, the result measured in the Example and the comparative example is put together in Tables 2-4, and is shown. [Examples 1 to 8] Silicone oils having the silicone composition ratios shown in Table 1 were prepared, and the vibration period difference T and the residual heating ratio R were obtained.
Was measured. The silicone component used in the preparation of the oil agent includes a part of a side chain of dimethyl silicone having a methyl group at a terminal, an amino group represented by the following chemical formula 1, an epoxy group represented by the following chemical formula 2, and an ethylene represented by the following chemical formula 3. Three types each substituted with an oxide group were used. The modification amounts were 1.0% by weight, 1.0% by weight, and 50% by weight, respectively. For 100 parts by weight of the above three types of silicone, 3
0 parts by weight of a nonionic surfactant and water were added, and the mixture was subjected to the above measurement by using a homomixer and a homogenizer to prepare a 30% by weight pure silicone oil.

[0050]

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[0051]

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[0052]

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Further, a copolymer consisting of 99.5% of acrylonitrile and 0.5 mol% of itaconic acid was polymerized by a solution polymerization method using dimethyl sulfoxide as a solvent, and the concentration was 2%.
A spinning dope of 2% was obtained. After the polymerization, the ammonia gas is adjusted to pH
By blowing to 8.5 to neutralize itaconic acid and introducing an ammonium group into the polymer component, the hydrophilicity of the spinning dope was improved. The obtained spinning dope was used for 40
Using a spinneret having a diameter of 0.15 mm and a number of holes of 4,000, once discharged into the air and allowed to pass through a space of about 4 mm, a coagulation bath composed of a 35% dimethyl sulfoxide aqueous solution controlled at 3 ° C. It was coagulated by dry-wet spinning. The obtained coagulated yarn is washed with water and then at 70 ° C.
Then, the silicone oil prepared in Example 1 was applied by stretching 3 times in hot water and passing through an oil bath. The concentration in the oil bath was adjusted by diluting with water so as to have a pure content of 2.0%. Further, using a heating roller at 180 ° C., a drying treatment for a contact time of 40 seconds was performed. The obtained dried yarn was stretched in a 0.4 MPa-G pressure steam to obtain an acrylic precursor having a total draw ratio of 14 times, a single yarn fineness of 0.8 dTex, and a single fiber count of 24,000. . The amount of the silicone oil applied to the obtained acrylic precursor was 1.0% in pure content, and the surface area ratio was 1.01.

The obtained acrylic precursor was converted to 240
In air at ２280 ° C., it was converted to a flame resistant yarn having a flame shrinkage retention of 80%. The flameproofing time was 40 minutes, and the stretching ratio in the flameproofing step was two types, 0.85 and 0.95. With respect to the obtained flame-resistant yarn, the stretchability in the preliminary carbonization step was measured.

Further, for the same flame-resistant yarn, 300 to
After preliminary carbonization in an inert atmosphere at 800 ° C., carbonization was performed at a maximum temperature of 1500 ° C. The stretching ratio in the preliminary carbonization step was 0.96 when the stretching ratio in the oxidation-resistant step was 0.85.
95 was 1.05. Further, the obtained carbonized yarn was subjected to anodizing treatment at 10 coulomb / g-CF in a sulfuric acid aqueous solution, and then the number of fluffs present in 20 m of carbon fiber, strength, and elastic modulus were measured. [Comparative Examples 1 to 3] Silicone oils having the silicone composition ratios of the oils shown in Table 1 were prepared, and the vibration cycle difference T, the residual heating rate R, the stretchability in the preliminary carbonization step, and the number of fluffs were obtained in the same manner as in Example 1. , Strength and elastic modulus were measured. However, the oxidized yarn treated at the oxidized draw ratio of 0.95 has a preliminary carbonized draw ratio of 1.0.
In No. 5, the thread was broken and the process could not be performed, so the operation was stopped.

Table 2 shows the properties of each oil agent.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

As is clear from Table 3, the comparative example had poor stretchability and many fluffs as compared with the example.
It can be seen that the strength is low. Example 9 The same procedure as in Example 3 was carried out except that the raw spinning solution was set to 70 ° C. and coagulated by wet spinning which was directly introduced into a coagulation bath consisting of a 70% aqueous dimethyl sulfoxide solution controlled at 70 ° C. Stretchability of carbonization process,
The number of fluff, strength, and elastic modulus were measured. In addition, the surface area ratio of the obtained acrylic precursor was 1.07. [Comparative Example 4] Extensibility, number of fluffs, strength and elastic modulus in the preliminary carbonization step were measured in the same manner as in Example 9 except that the silicone oil agent prepared in Comparative Example 2 was used.

[0061]

[Table 4]

[0062]

According to the present invention, it is possible to effectively suppress uneven firing in the flame-proofing step, and to provide a high-performance carbon fiber with high productivity.

Claims (6)

[Claims] 1. A silicone oil for producing an acrylic precursor for carbon fiber, wherein a vibration period difference T of a pendulum measured by a free damping vibration method of a rigid pendulum satisfies the following equation. 0.03 ≦ T ≦ 0.4 T = T30−T180 T30: Vibration period (second) at 30 ° C. T180: Vibration period (second) after heat treatment at 180 ° C. for 10 minutes 2. An amino-modified silicone having a viscosity at 25 ° C. of 500 to 10,000 cSt, and a viscosity at 25 ° C. of 1,000 to 30,000 cSt.
Epoxy-modified silicone having a viscosity at 25 ° C. of 2
A water emulsion containing three types of 0 to 1000 cSt alkylene oxide-modified silicone, wherein the ratio of epoxy-modified silicone to 10 parts by weight of amino-modified silicone is 10 to 80 parts by weight, and 100 parts by weight of all silicone compounds. The silicone oil agent for producing an acrylic precursor for carbon fibers according to claim 1, wherein the ratio of the alkylene oxide-modified silicone to the polyester is from 0.5 to 10 parts by weight. 3. An amino-modified silicone having a viscosity at 25 ° C. of 700 to 7000 cSt,
An epoxy-modified silicone having a viscosity at 25 ° C of 5,000 to 20,000 cSt and a viscosity at 25 ° C of 50 to
3. A water emulsion containing three types of 800 cSt alkylene oxide-modified silicone.
The silicone oil agent for producing an acrylic precursor for carbon fiber according to the above. 4. After applying the silicone oil according to any one of claims 1 to 3 to a water-swollen yarn,
The acrylic precursor for carbon fiber obtained by heat treatment at a temperature of 00 ° C. is made flame-resistant in an oxidizing atmosphere of 200 to 300 ° C., and then pre-carbonized in an inert atmosphere of 300 to 800 ° C., and further 800 to 1800 ° C. Carbonizing in an inert atmosphere as described above. 5. The carbon fiber acrylic precursor has a surface area ratio measured by an atomic force microscope of from 1.00 to 1.00.
The method for producing carbon fiber according to claim 4, wherein the value is 1.05. 6. The method according to claim 1, wherein the stretching ratio in said flame-proofing step is 0.90
1.05, stretching ratio in pre-carbonization step is 0.98 ~
The method for producing carbon fiber according to claim 4, wherein the value is 1.10.