JPH06184830A - Precursor fiber bundle for carbon fiber - Google Patents

Abstract

(57) [Summary] [Structure] Copolymerization of monofunctional siloxane and / or difunctional siloxane with trifunctional siloxane and / or tetrafunctional siloxane An oil agent consisting of a silicone resin is contained in an amount of 0.05 to 0. A precursor fiber bundle for carbon fibers, characterized by containing 5% by weight. Polysiloxane having monofunctional siloxane and / or difunctional siloxane as a repeating unit and trifunctional siloxane and / or 4
A precursor fiber bundle for carbon fiber, which contains 0.05 to 0.5% by weight based on the total weight of the fiber of an oil agent made of a silicone resin mixed with a polysiloxane having a functional siloxane as a repeating unit. [Effect] Adhesion between single fibers can be prevented by applying a small amount of an oil agent, and high-strength, high-quality carbon fibers can be manufactured with good processability.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a precursor fiber bundle for carbon fibers. More specifically, the present invention relates to a precursor fiber bundle for carbon fibers for producing high-strength, high-strength carbon fibers having good processability.

[0002]

2. Description of the Related Art Carbon fiber has high mechanical properties by forming a composite with a so-called 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 it is required to provide carbon fiber having high specific strength and high specific elastic modulus at low cost.

Carbon fiber is an acrylic resin, which is its precursor,
200 ~ 30 by spinning rayon fiber, pitch fiber, etc.
After a flameproofing step of heating and firing in an oxidizing atmosphere at 0 ° C. to convert to oxidized fibers, it is further heated to 300 to 3000 ° C. in an inert atmosphere such as nitrogen, argon or helium or in a vacuum to carbonize and / or A method of manufacturing by undergoing a graphitization process is widely adopted industrially.

It is said that the tensile strength (hereinafter referred to as strength) in the fiber axis direction, which is a basic characteristic of carbon fiber, is governed by the size and number of defects in the carbon fiber. The causes of this defect are voids and foreign substances inside the precursor fiber, scratches on the surface of the precursor fiber and adhesion between single fibers, a flame resistance step that is a step of converting the precursor fiber into carbon fiber, pre-carbonization. The occurrence of adhesion between single fibers in the process may be mentioned. In particular, the bond between the single fibers has a significant decrease in strength and, in the extreme case, fluff occurs frequently, and in extreme cases, the process cannot be passed at all. It is extremely important to prevent adhesion between fibers.

In the flame resistance and pre-carbonization steps, it is necessary to set the temperature rising rate as gently as possible in order to prevent the adhesion between the single fibers, which is one of the causes of low productivity of carbon fibers. .

For this reason, in the precursor fiber production process, it has become common to apply a silicone-based oil agent having high heat resistance and excellent releasability to the fiber surface.

This silicone-based oil agent exhibits excellent heat resistance in the flame-proofing process, but in the pre-carbonization process, the weight of the fiber is drastically reduced and single fiber-to-fiber bonding is very likely to occur.
In the temperature range of 0 to 500 ° C., the heat resistance is insufficient, and most of the silicone decomposes and scatters, so it is necessary to apply a large amount of oil agent in advance. Therefore, there is a problem that the oil agent is deposited on the rollers and guides in each process to deteriorate the process passability, and a large amount of decomposed gas is generated in the firing process, so that the strength of the carbon fiber itself is lowered.

Inorganic fine particles can be used as a material that can withstand a temperature of 400 to 500 ° C. in an inert atmosphere.
A method of applying the inorganic fine particles to the surface of the precursor fiber is proposed in, for example, Japanese Patent Publication No. 52-39455.
This uses solid fine particles of 5 to 0.01 micron, but while the fine particle-added fibers are turned by many rollers and guides before being converted into carbon fibers, this hard The fine particles damage the fiber surface, which becomes a defect, and the strength between the single fibers is not improved although the adhesion between the single fibers is improved. In an extreme case, fluff occurs and the strength decreases.

It is known that polysiloxane generally increases in hardness and heat resistance as the atomic ratio of carbon to silicon (C / Si) decreases. At present, the commonly used silicone-based oil agent is composed of a linear polysiloxane having a bifunctional siloxane (R ₂ SiO _2/2 ) as a repeating unit, and can be easily used in a high temperature inert atmosphere. Since it decomposes and scatters, 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 the main chain has a network structure and also has a low C / Si ratio, and therefore has heat resistance. Becomes higher.

By the way, since a silicone resin mainly containing a trifunctional siloxane and / or a tetrafunctional siloxane is very hard, the fiber surface is damaged, and although the effect of preventing the adhesion between single fibers is great, the strength of the carbon fiber is not improved. There is a first drawback. In addition, the dispersion stability when dispersed in water is poor, and it is difficult to uniformly adhere to the fibers.
In addition, there is a third drawback that the resin is resinized after water is evaporated and is deposited on the roller surface to deteriorate the fiber processability.

[0011]

The problem to be solved by the present invention is to solve the above-mentioned drawbacks of the prior art, that is, to prevent adhesion between single fibers by adding a small amount of oil, and to improve high strength. It is an object of the present invention to provide a method for producing a precursor fiber bundle for producing a high-quality carbon fiber with good processability.

[0012]

In order to solve the above problems, the precursor fiber bundle for carbon fibers of the present invention has one of the following configurations. 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 fiber as the total Si. Characteristic carbon fiber precursor fiber bundle,
Alternatively, an oil agent comprising a mixed silicone resin of a polysiloxane having a monofunctional siloxane and / or a difunctional siloxane as a repeating unit and a polysiloxane having a trifunctional siloxane and / or a tetrafunctional siloxane as a repeating unit is used as all Si, and the weight per fiber weight is The precursor fiber bundle for carbon fiber is characterized by containing 0.05 to 0.5% by weight.

The present invention will be described in more detail below.

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

The first drawback of the prior art described above cannot be solved without using an oil agent made of any one of these silicone resins.

The content of the oil agent made of any of these silicone resins in the precursor fiber bundle is
i is 0.05 to 0.5% by weight based on the weight of the fiber. Here, the content per weight of fibers as total Si refers to a value obtained by an ordinary method by elemental analysis. If this 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 anti-adhesion effect 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 _{2 P} spectrum in X-ray photoelectron spectroscopy (ESCA) is The presence of 20 to 70% with respect to the total Si is preferable from the viewpoint of preventing the resin hardness from being too hard, while preventing the effect of preventing adhesion between single fibers from becoming poor due to insufficient heat resistance.

The composition of Si is analyzed by ES manufactured by Kokusai Electric Co., Ltd.
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 degree: 10 ⁻⁸ Torr Kinetic energy (K, E) correction: The kinetic energy of the main peak of C _1S is adjusted to 1202.0 ev.

Peak division: The peak of the Si _{2 P} spectrum is divided as follows.

Bifunctional siloxane: 1384.6 ev Trifunctional siloxane: 1384.1 ev Tetrafunctional siloxane: 1383.2 ev Incidentally, the proportion of monofunctional siloxane and / or difunctional siloxane co-overloaded with trifunctional siloxane and / or tetrafunctional siloxane. The hardness and heat resistance of the copolymer silicone resin itself can be adjusted by. 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 from being insufficient and the effect of preventing adhesion between single fibers from becoming poor,
The range of about 20 to 70 mol% is preferable.

The copolymer silicone resin is made into a glycol component-modified resin obtained by reacting ethylene oxide (hereinafter EO) and / or propylene oxide (hereinafter PO) with a trifunctional siloxane and / or
Alternatively, it is particularly preferable because it can alleviate the above-mentioned three drawbacks of the silicone resin mainly composed of tetrafunctional siloxane at one time. That is, the dispersion stability and the uniform adherence to the fibers can be improved, and therefore 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 glycole component is decomposed, there is also an effect that resin deposition on the roller surface in the yarn making process or the like can be improved. The optimum amount of modification to the glycol component is not constant depending on the siloxane composition and the EO / PO ratio, but the water-soluble or self-emulsifying property is excellent, while the heat-resistant resin component that has the effect of preventing adhesion between single fibers is selected. From the viewpoint of sufficient inclusion, it is generally 40-70.
A range of wt% is preferred.

The term "self-emulsifying property" as used herein means that it is added to water kept at 25 ° C. so as to have a concentration of 0.1 wt%, stirred for 30 minutes with a homomixer, and allowed to stand for 24 hours without any precipitate or layer separation. Say.

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

The precursor fiber bundle is not particularly limited, but it is preferably applied to a pitch type or acrylonitrile type precursor fiber bundle. The spinning method of the acrylonitrile-based precursor fiber bundle may be any of wet method, dry-wet method, and dry method. Particularly, the fiber obtained by the dry-wet spinning method has an extremely smooth surface and the single fibers are easily brought into surface contact with each other to easily adhere to each other. The effect of the present invention is remarkable and is more preferable.

[0026]

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

(Example 1) A 20% by weight DMSO solution of a PAN-based copolymer consisting of 99.3% by weight of acrylonitrile and 0.7% by weight of itaconic acid was used as a spinning stock solution. The stock solution viscosity was 650 poise at 45 ° C. This spinning dope was discharged from a spinneret having 3000 small holes with a diameter of 0.12 mm, and after passing through a space of 3 mm, DMSO /
Lead it into the coagulation liquid where the weight ratio of water is set to 30/70,
Dry-wet spinning was performed at a take-up speed of 13 m / min. afterwards,
Wash with water, pass the thread stretched 3 times in a warm water bath through an oil bath,
After squeezing excess oil with a nip roller, the surface temperature is 120
Drying and densifying with a drying drum at ℃, steam pressure is 5k
A precursor fiber bundle of 3000 filaments having a single yarn fineness of 1 denier was obtained by drawing 4 times with a pressure steam drawing machine of g / cm ² · G. This precursor fiber bundle was flameproofed by a conventional method and carbonized at 1450 ° C. to obtain carbon fiber. Here, as the oil bath, monofunctional siloxane: tetrafunctional siloxane =
1: 1 polymer modified with EO and PO by 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 after carbon fiber impregnation and curing of epoxy resin is 490kg
It was as high as f / mm ² . The precursor manufacturing process and the firing process were good without any trouble.

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

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

The Si content of the precursor fiber bundle is 0.21 wt.
%Met. The carbon fiber was extremely flexible without adhesion between single fibers, but the tensile strength was low at 380 kgf / mm ² . In addition, a large amount of resinized resin was accumulated on the surface of the drying drum after applying the oil agent, and there were many problems in which single fibers were wrapped around.

Example 2 Example 1 was repeated except that an oil bath was prepared by changing the ratio of siloxane (R: methyl group) in the composition shown in Table 1 to prepare a copolymer and dispersing it in water.
The precursor fiber bundle was flame-proofed in the same manner as in
Carbonization was performed at 50 ° C. to obtain carbon fibers.

[0032]

[Table 1] For the precursor fiber bundle, the compositional analysis of Si by ESCA and the adhesion amount of Si by elemental analysis are shown, and for the carbon fiber, the tensile strength after resin impregnation / curing is measured and summarized in Table 2.

[0033]

[Table 2] In Comparative Example 3 shown in Table 2, fluff was generated due to the adhesion between single fibers in the carbonization step, 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 frequently occurred in the flameproofing / carbonization process, and the strength was also low. In Comparative Example 5, the effect of preventing adhesion between single fibers was extremely good, but there were many troubles such as fluff generation due to the accumulation of resin on the roller surface in the yarn making process,
In addition, tar was often generated in the firing process. On the other hand, in the range of the examples of the present invention, there were no process troubles and high-quality and high-strength carbon fibers were obtained.

[0034]

EFFECTS OF THE INVENTION The precursor fiber bundle of the present invention can prevent adhesion between single fibers by adding a small amount of an oil agent and can produce high-strength, high-quality carbon fibers with good processability.

Claims (4)

[Claims] 1. 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 used as a total S agent.
A precursor fiber bundle for carbon fibers, characterized in that it is contained in an amount of 0.05 to 0.5% by weight based on the fiber weight as i. 2. The copolymerized silicone resin of monofunctional siloxane and / or difunctional siloxane with trifunctional siloxane and / or tetrafunctional siloxane is a glycol-modified silicone resin. Precursor fiber bundle for carbon fiber. 3. An oil agent comprising a mixed silicone resin of a polysiloxane having a monofunctional siloxane and / or a difunctional siloxane as a repeating unit and a polysiloxane having a trifunctional siloxane and / or a tetrafunctional siloxane as a repeating unit as all Si. 0.05 to 0. per fiber weight.
A precursor fiber bundle for carbon fibers, characterized by containing 5% by weight. 4. S in X-ray photoelectron spectroscopy (ESCA)
The Si component of the trifunctional siloxane and / or the tetrafunctional siloxane obtained by peak division of the i _{2 P} spectrum is all Si
20 to 70% by weight, and 0.05 to 0.5% by weight as the total Si based on the weight of the fiber. Precursor fiber bundle for carbon fiber according to claim 1 or 3, characterized in that .