JPS59144621A - Carbon fiber having improved elongation - Google Patents

Abstract

PURPOSE:Carbon fibers, containing silicon present between crystals of graphite constituting the carbon fibers, having improved elongation, and useful for members of aircraft, ships, etc. CONSTITUTION:Carbon fibers, obtained by melting a pitch, e.g. petroleum pitch or coal tar pitch, adding and reacting preferably 10wt% or more (expressed in terms of silicon) silicon compound, e.g. a silicon halide, vinylsilicon compound or alkoxide of silicon, etc. with the molten pitch in the inert atmosphere, and spinning the resultant reaction porduct in a melt spinning apparatus, and containing silicon present between crystals of graphite constituting the carbon fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to carbon fibers with improved elongation, particularly carbon fibers using pitch as a carbon source.

Carbon fibers are increasingly being used as reinforcement for various synthetic resins, particularly in parts for aircraft, ships, etc., which require a high modulus of elasticity that cannot be obtained with glass fiber reinforcement.

Conventional methods for producing carbon fiber include a method using polyacrylonitrile as a carbon source and a method using pitch obtained from petroleum or the like. However, the former method has the disadvantage that polyacrylonitrile is expensive, sb, and manufacturing costs are high. In addition, reinforced resin bodies using such fibers, for example, do not have very high impact resistance and are relatively easy to break. . This is because carbon fibers have a low elongation rate and are therefore relatively easily cut.

Furthermore, the latter method generally has somewhat lower physical properties than the fibers obtained by the former method, and its elongation rate and stiffness are also lower than those of the fibers obtained by the former method.

As a result of various studies and examinations aimed at effectively improving the elongation rate of these carbon fibers, the company discovered that the above objective could be achieved by improving the bonding state between the graphites that make up the fibers. . Thus, the present invention provides a carbon fiber with improved elongation, characterized by interposing silicon between the graphite crystals constituting the carbon fiber.

In the present invention, as a means for interposing silicon between graphite crystals, for example, a method of reacting a silicon halide, a vinyl silicon compound, a silicon alkoxide, etc. with pitch can be adopted, and in this case, the reaction conditions are as follows. Pitch can be melted in a bath and reacted with these silicon compounds in a liquid or gas-liquid state under an inert atmosphere. Alternatively, a method of melt-mixing an organosilicon compound such as polycarbosilane, polysilane, siloxane, polysilazane, etc. with pitch under an inert atmosphere may be employed as appropriate. In these reactions, it is sufficient for b of the silicon compound to be used to be up to about 30 weight i2, f4 or 10 M, calculated as silicon. These electric currents are related to the elongation rate of the carbon fiber that is to be obtained, but if too many are present, some of them will impede the desirable R34 physical properties inherent to the anthracite fiber. do not have.

As the pitch used in the present invention, various pitches can be used as appropriate, such as, for example, each type of pitch, coal tar pitch, and vinyl chloride pitch. When these pitches are reacted with a silicon compound, impurities are generally removed by filtration or centrifugation, and then polycondensation is performed by heat treatment or under the action of a catalyst according to a conventional method. Thereafter, if necessary, cine essentials are separated by filtration, centrifugation, etc.

The silicon compound can be mixed into the pitch during the polycondensation step, or can be mixed after the polycondensation.

After the pitch and the silicon compound are reacted or melt-mixed, they are spun according to a conventional method. The fiber surface is then oxidized in an oxidizing atmosphere to render it non-fusible, followed by sufficient carbonization and crystallization in an inert atmosphere. Carbonization and crystallization can be carried out continuously, but the steps can also be carried out separately.

Next, the present invention will be explained using examples.

Example 1 Using fluidized catalytic cracking residual pitch as a raw material, pitch was thermally modified according to a conventional method to prepare a pitch containing 15% of quinolinous solution. To 90 parts of this pitch, 10 parts of polycarbosilane (molecular weight approximately io, ooo, synthesized by conventional method using dimethyldichlorosilane as a raw material by l-1,1 ram reduction and thermal isomerization) was added. The mixture was melted and mixed at 350° C. under a nitrogen atmosphere. This was extruded and spun using a bath melt spinning device having 20 nozzles of 058 ψ. At this time, the spinning temperature was 33
The temperature was 0°C, and the fiber winding speed was 500 m/min.

The obtained fibers were kept wound up in a hot air circulation type dryer, heated to 300°C at a heating rate of 5°C, and kept there for 5 hours. The treatment during this time was carried out in air. After cooling, the pig iron was taken out, rolled, and heat-treated by continuously passing it through an electric furnace consisting of two furnace chambers for 1 hour.

The first chamber of this electric furnace was replaced with a nitrogen accumulation chamber of 300
In a furnace chamber with a temperature distribution of ~800°C, a residence time of 30 minutes was allowed in the temperature zone (800°C) in which the heating rate of the fibers exceeded 10~bii.Second The chamber was a furnace room with a temperature distribution of 800 to 2000°C, which was replaced with an argon atmosphere, and the fibers were allowed to stay there for 5 minutes at a heating rate of 50°C to 2000°C. Carbon fiber has a tensile strength of 9s
50 kV/mm”, elastic modulus 26 t/rttyn2
, the elongation at break was 2.1%. Next, use standard epoxy resin DX-210 to adjust the lamination direction of the fibers to O'
A multilayer laminated fiber reinforced body was prepared by laminating 8 units of +45° and 90°, 24 layers in total, and an Izot impact test was conducted. Impact value (with notch) is 2
．． It was 8kl/・pot/d.

Example 2 Using fluidized catalytic cracking residual pitch as a raw material, it was thermally modified according to a conventional method to prepare a pitch containing 15 quinolinous solubles. This pitch was melted at 350° C. under a nitrogen atmosphere, and silicon tetrachloride gas was blown in an amount of 10 weight jIt% based on the pinch for 30 minutes, and then cooled and solidified. Using this pitch, spinning and heat treatment similar to those in Example 1 were performed to obtain carbon fibers. This fiber has tensile strength so OK
22 elastic modulus 25t/q2. The elongation at break was 20.

Comparative Example A carbon fiber obtained by the same treatment as in Example 1 except that no polycarbosilane was added had a tensile strength of 200 h9/t2.
2 elasticity modulus 40 t/lrm" r breaking elongation 06 metal attack. Using this, a similar fiber reinforced body was made and subjected to Izot impact test. Izot impact value (with notch)
is 1.2 kq・- pieces.

Claims (1)

[Claims] 1. A carbon fiber with improved elongation, characterized by interposing silicon between graphite crystals constituting the carbon fiber. 2. Carbon fibers in the glaze range (1), where the graphite source constituting the carbon fibers is pitch.