JP2850676B2 - Precursor fiber bundle for carbon fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precursor fiber bundle for carbon fibers. More specifically, the present invention relates to a carbon fiber precursor fiber bundle for producing high-quality carbon fiber with high quality and good process passability.

[0002]

2. Description of the Related Art Carbon fiber has a high degree of mechanical properties by forming a composite with a matrix material such as a thermosetting resin or a thermoplastic resin. -It has been widely used in leisure, civil engineering and construction related fields, and there is a demand for inexpensive provision of carbon fibers having high specific strength and specific elastic modulus.

[0003] Carbon fiber is a precursor of acrylic,
Spinning rayon fiber, pitch fiber, etc., 200 ~ 30
After passing through a flame-proofing step of heating and burning in an oxidizing atmosphere at 0 ° C. to convert it to oxidized fiber, it is further heated to 300 to 3000 ° C. in an inert atmosphere such as nitrogen, argon, helium or vacuum to carbonize and / or A method of manufacturing by a graphitization step is widely used industrially.

[0004] It is said that tensile strength in the fiber axis direction (hereinafter referred to as "strength"), which is a basic property of carbon fibers, is governed by the size and number of defects in carbon fibers. Causes of this defect include voids and foreign substances inside the precursor fiber, scratches on the surface of the precursor fiber and adhesion between the single fibers, a flame-proofing step in which the precursor fiber is baked and converted into carbon fiber, and a pre-carbonization step. Occurrence of adhesion between single fibers in the process. In particular, the adhesion between the single fibers has a remarkable decrease in strength, and in addition, many fluffs occur in the firing step. In an extreme case, the fibers cannot pass through the step at all. It is very important to prevent adhesion between the fibers.

[0005] In the flame resistance and pre-carbonization steps, it is necessary to set the heating rate as slowly as possible in order to prevent the adhesion between the single fibers, which contributes to the low productivity of carbon fibers. .

[0006] For this reason, it is common to apply a silicone oil agent having high heat resistance and excellent release properties to the fiber surface in the precursor fiber production process.

Although this silicone oil exhibits excellent heat resistance in the flame-proofing step, the weight of the fiber is sharply reduced in the pre-carbonization step, so that adhesion between single fibers is extremely likely to occur.
In a temperature range of 0 to 500 ° C., heat resistance is insufficient, and most of the silicone is decomposed and scattered, so it is necessary to apply a large amount of an oil agent in advance. For this reason, there is a problem that the oil agent accumulates on the rollers and guides in each process, which deteriorates the processability, and that a large amount of decomposition gas is generated in the firing process, thereby lowering the strength of the carbon fiber itself.

[0008] Inorganic fine particles can be used in an inert atmosphere at a temperature of 400 to 500 ° C.
A method of applying inorganic fine particles to the surface of the precursor fiber has been proposed in, for example, Japanese Patent Publication No. 52-39455.
This uses solid fine particles of 5 to 0.01 microns, but the fibers to which the fine particles have been applied are drawn by a number of rollers and guides before being converted into carbon fibers. The fiber surface is damaged by the fine particles, which becomes a defect, and the strength is not improved even though the adhesion between the single fibers is improved. In an extreme case, there is a problem that fluff is generated and the strength is reduced.

It is also known that polysiloxane generally increases in hardness and heat resistance as the atomic ratio of carbon to silicon (C / Si) decreases. At present, silicone oils generally used are composed of a linear polysiloxane having a bifunctional siloxane (R ₂ SiO _2/2 ) as a repeating unit, and can be easily prepared in a high-temperature inert atmosphere. Due to decomposition and scattering, the effect of protecting the fiber surface and preventing adhesion between single fibers is insufficient. On the other hand, a silicone resin having a trifunctional siloxane (RSiO _3/2 ) and / or a tetrafunctional siloxane (SiO _4/2 ) in a part of a main chain has a network structure and has a small C / Si ratio, and thus has heat resistance. Will be higher.

[0010] By the way, since the silicone resin mainly composed of trifunctional siloxane and / or tetrafunctional siloxane is very hard, it damages the fiber surface and does not improve the strength of the carbon fiber despite the large effect of preventing adhesion between single fibers. There is a first disadvantage. In addition, the dispersion stability is poor when dispersed in water, making it difficult to uniformly adhere to fibers.
In addition, there is a third disadvantage that water evaporates and turns into resin after being evaporated, and is deposited on the roller surface to deteriorate the processability of fibers.

The problem to be solved by the present invention is to solve the above-mentioned drawbacks of the prior art, that is, by applying a small amount of an oil agent to prevent adhesion between single fibers, and to obtain high-strength, high-grade carbon fibers. An object of the present invention is to provide a method for manufacturing a precursor fiber bundle for manufacturing with good process passability.

[0012] In order to solve the above problems, the precursor fiber bundle for carbon fiber of the present invention has any one of the following constitutions. That is, an oil agent comprising a copolymerized silicone resin of a monofunctional siloxane and / or a bifunctional siloxane and a trifunctional siloxane and / or a tetrafunctional siloxane is contained in an amount of 0.05 to 0.5% by weight based on the weight of the fiber as total Si ; X
Si _2p spectrum in X-ray photoelectron spectroscopy (ESCA)
And / or trifunctional siloxane obtained by peak separation of
Means that the Si component of the tetrafunctional siloxane is 20 to
A precursor fiber bundle for carbon fiber characterized by being present in 70% , or a polysiloxane having a repeating unit of a monofunctional siloxane and / or a bifunctional siloxane and a repeating unit of a trifunctional siloxane and / or a tetrafunctional siloxane. An oil agent composed of a silicone resin mixed with polysiloxane is used as a total Si in an amount of 0.05 to 0.
5% by weight and X-ray photoelectron spectroscopy (ESCA)
Functionality obtained by peak splitting of Si _2p spectrum in
Si component of siloxane and / or tetrafunctional siloxane
Is a precursor fiber bundle for carbon fibers , wherein 20 to 70% of the total Si is present.

Hereinafter, the present invention will be described in more detail.

As an active ingredient of the oil agent used in the present invention, any one of the following silicone resins is used. That is, the monofunctional siloxane (R
₃ SiO _1/2 ) and / or bifunctional siloxane (R ₂
Copolymerized silicone of monofunctional siloxane and / or bifunctional siloxane with trifunctional siloxane and / or tetrafunctional siloxane, obtained by copolymerizing an appropriate amount of SiO _2/2 ) with trifunctional siloxane and / or tetrafunctional siloxane. It is a resin or a mixed silicone resin of a polysiloxane having repeating units of monofunctional siloxane and / or bifunctional siloxane and a polysiloxane having repeating units of trifunctional siloxane and / or tetrafunctional siloxane.

The above-mentioned first disadvantage of the prior art cannot be solved unless an oil agent composed of any of these or any of the silicone resins is used.

The content of the oil agent comprising any one of these silicone resins in the precursor fiber bundle is set to
i is 0.05 to 0.5% by weight per fiber weight. Here, the content per fiber weight as total Si refers to a value obtained by an elemental analysis by an ordinary method. When the content is less than 0.05% by weight, there is a problem that the effect of preventing adhesion between single fibers becomes insufficient. On the other hand, when the content exceeds 0.5% by weight, the effect of preventing adhesion is saturated.

Further , in the above-mentioned copolymerized silicone resin or mixed silicone resin, the Si component of trifunctional siloxane and / or tetrafunctional siloxane obtained by peak division of Si _2p spectrum in X-ray photoelectron spectroscopy (ESCA) is used. those present 20% to 70% relative to the total Si is, while preventing the resin hardness is too hard, from the viewpoint of preventing the single fiber adhesion preventing effect is insufficient heat resistance becomes poor, it is necessary.

The composition analysis of Si was performed by ES manufactured by Kokusai Electric Inc.
It is carried out under the following conditions using a -200 type X-ray photoelectron spectrometer.

Excited X-ray: AlKα1,2 ray (1486.6)
ev) X-ray output: 8 kv, 20 mA Temperature: 40 ° C. Vacuum: 10 ⁻⁸ Torr Kinetic energy (K, E) correction: Adjust the kinetic energy of the main peak of C _1S to 1202.0 ev.

Peak division: The peak of the Si _2P spectrum is divided as follows.

Bifunctional siloxane: 1384.6 ev Trifunctional siloxane: 1384.1 ev Tetrafunctional siloxane: 1383.2 ev The proportion of monofunctional siloxane and / or bifunctional siloxane to trifunctional siloxane and / or tetrafunctional siloxane Thereby, the hardness and heat resistance of the copolymerized silicone resin itself can be adjusted. Although the copolymerization ratio of the monofunctional siloxane and / or the bifunctional siloxane is not constant depending on the combination of the respective siloxanes,
While preventing the resin hardness from being too hard, from the viewpoint of preventing heat resistance is insufficient and the effect of preventing adhesion between single fibers from becoming poor,
A range of about 20 to 70 mol% is preferred.

When the copolymerized silicone resin is converted into a glycol component-modified resin obtained by reacting ethylene oxide (hereinafter, referred to as EO) and / or propylene oxide (hereinafter, referred to as PO), trifunctional siloxane and / or
Alternatively, the above three disadvantages of the silicone resin mainly composed of a tetrafunctional siloxane can be improved at a time, which is particularly preferable. That is, since the dispersion stability and the uniform adhesion to fibers can be improved, water solubility or self-emulsification can be imparted, which is preferable. Further, in this case, since resinification is suppressed up to the heat treatment temperature at which the glycol component decomposes, the resin has an effect of improving the accumulation of resin on the roller surface in a yarn-forming step or the like. The optimum amount of modification to the glycol component is not constant depending on the siloxane composition, EO / PO ratio, etc., but the water-soluble or self-emulsifying property is excellent, while the heat-resistant resin component having the effect of preventing adhesion between single fibers is used. From the viewpoint of sufficient inclusion, approximately 40 to 70
A range of wt% is preferred.

Here, the term "self-emulsifying property" means that a solution is added to water kept at 25 ° C. so as to have a concentration of 0.1% by weight, stirred for 30 minutes with a homomixer and left for 24 hours without any precipitate or layer separation. Say.

The silicone resin modified with a glycol component can be dissolved or emulsified in water to adjust the concentration and adhere to the fiber. Further, as long as the object of the present invention is not impaired, it can be mixed with other general silicone oils and non-silicone oils.

The precursor fiber bundle is not particularly limited, but is preferably applied to a pitch-based or acrylonitrile-based precursor fiber bundle. The acrylonitrile-based precursor fiber bundle can be wet-spun, dry-wet, or dry, but the fiber obtained by the dry-wet spinning method has a very smooth surface and the single fibers are in surface contact with each other and easily adhere. The effect of the present invention is remarkable and more preferable.

[0026]

The present invention will be specifically described below with reference to examples.

Example 1 A 20% by weight DMSO solution of a PAN copolymer composed of 99.3% by weight of acrylonitrile and 0.7% by weight of itaconic acid was used as a spinning dope. Stock viscosity was 650 poise at 45 ° C. This spinning stock solution is discharged from a spinneret having 3,000 small holes having a diameter of 0.12 mm, and after passing through a space of 3 mm, DMSO /
Lead into the coagulation liquid with the weight ratio of water set to 30/70,
Dry-wet spinning was performed at a take-up speed of 13 m / min. afterwards,
After washing with water and passing the yarn stretched 3 times in a warm water bath through an oil bath,
After squeezing excess oil with a nip roller,
Drying and densification with a drying drum at ℃, steam pressure 5k
It was stretched 4 times with a pressurized steam stretching machine of g / cm ² · G to obtain a precursor fiber bundle of single filament fineness of 1 denier and 3000 filaments. This precursor fiber bundle was made flame-resistant by a conventional method, and carbonized at 1450 ° C. to obtain carbon fibers. Here, as the oil bath, monofunctional siloxane: tetrafunctional siloxane =
A 1: 1 polymer was modified with EO and PO at 60 wt% (E
A 4 wt% aqueous solution of glycol modified silicone resin (O: PO = 1: 1) was used. As a result of elemental analysis of the precursor fiber bundle, the Si content was 0.2 wt%. Tensile strength of carbon fiber after epoxy resin impregnation and curing is 490kg
It was as high as f / mm ² . The precursor production process and the firing process were good without any trouble.

(Comparative Example 1) The same procedure as in Example was carried out except that a 4 wt% aqueous solution of EO-modified silicone obtained by modifying dimethyl silicone with EO by 60 wt% was used as an oil bath. The Si content of the precursor fiber bundle was 0.23 wt%. The tensile strength of the carbon fiber was as low as 332 kgf / mm ² , and the single fiber was bonded in the flame-proofing and pre-carbonization step, and fluff was frequently generated in the carbonization step.

(Comparative Example 2) The same operation as in Example 1 was carried out except that a silicone resin mainly composed of trifunctional siloxane was used as an oil bath and dispersed in water at 2.5 wt% using an emulsifier.

The Si content of the precursor fiber bundle is 0.21 wt.
%Met. The carbon fiber was extremely pliable without adhesion between single fibers, but the tensile strength was as low as 380 kgf / mm ² . In addition, a large amount of resinized resin was deposited on the surface of the drying drum after the oil agent was applied, and there were many problems that single fibers were wound.

Example 2 A copolymer was prepared as an oil bath by changing the ratio of siloxane (R: methyl group) with the composition shown in Table 1 and dispersed in water.
The precursor fiber bundle is made to be flame-resistant by a conventional method in the same manner as described above.
Carbonized at 50 ° C. to obtain carbon fibers.

[0032]

[Table 1] For the precursor fiber bundles, the compositional analysis of Si by ESCA and the amount of Si attached by elemental analysis were performed, and for the carbon fibers, the tensile strength after resin impregnation and curing was measured and the results are shown in Table 2.

[0033]

[Table 2] In Comparative Example 3 shown in Table 2, since the adhesion between the single fibers occurred in the carbonization step, fluff occurred and the strength was low. In Comparative Examples 4 and 6, the effect of preventing adhesion between single fibers was extremely good, but there were many troubles in which fluff was frequently generated in the flame-proofing / carbonization step, and the strength was low. In Comparative Example 5, the effect of preventing adhesion between single fibers was extremely good, but there were many troubles of generation of fluff due to resin deposition on the roller surface in the spinning process.
In addition, tar was often generated in the firing step. On the other hand, in the range of the examples of the present invention, high-quality, high-strength carbon fibers were obtained without any trouble in the process.

[0034]

By the precursor fiber bundle of the present invention, adhesion between single fibers can be prevented by applying a small amount of oil agent, and high strength and high quality carbon fibers can be produced with good processability.

Claims (3)

(57) [Claims] 1. An oil agent comprising a silicone resin copolymerized with a monofunctional siloxane and / or a bifunctional siloxane and a trifunctional siloxane and / or a tetrafunctional siloxane,
containing 0.05 to 0.5% by weight per fiber weight as i ,
Si _2p space and X-ray photoelectron spectroscopy in (ESCA)
Trifunctional siloxane obtained by Kutl's peak splitting and
// Si component of tetrafunctional siloxane is relative to all Si
A precursor fiber bundle for carbon fiber, which is present in an amount of 20 to 70% . 2. The silicone resin according to claim 1, wherein the copolymerized silicone resin of a monofunctional siloxane and / or a bifunctional siloxane and a trifunctional siloxane and / or a tetrafunctional siloxane is a silicone resin modified with glycol. Precursor fiber bundle for carbon fiber. 3. An oil agent comprising a mixed silicone resin of a polysiloxane having a repeating unit of a monofunctional siloxane and / or a bifunctional siloxane and a polysiloxane having a repeating unit of a trifunctional siloxane and / or a tetrafunctional siloxane is defined as total Si. 0.05-0.
5% by weight and X-ray photoelectron spectroscopy (ESCA)
Functionality obtained by peak splitting of Si _2p spectrum in
Si component of siloxane and / or tetrafunctional siloxane
Is present in an amount of 20 to 70% based on the total Si .