JPH0274621A - Graphitized fiber having low density and high elastic modulus - Google Patents

Abstract

PURPOSE:To provide the subject fiber having specified density and tensile elastic modulus, having extremely high specific elastic modulus owing to low density and high elastic modulus and suitable for aerospace used and fishing rod. CONSTITUTION:The objective fiber has a density of <=1.7g/cm<3> and a tensile elastic modulus of >=45t/mm<2>. The fiber can be produced e.g., by spinning an acrylic polymer by wet and dry spinning process, drawing the obtained coagulated fiber in hot water, subjecting the resultant precursor to flame-resistant treatment in an oxidizing atmosphere at 240-300 deg.C until the density reaches >=1.35g/cm<3> and calcining the flame-resistant fiber in an inert atmosphere at the maximum temperature of 2300-2900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to high-performance graphitized fibers, particularly graphitized fibers with low density, high elastic modulus, and high specific elastic modulus.

[Prior Art] In recent years, as the applications of graphitized fibers have expanded, there has been an increasing demand for improvements in specific modulus. In other words, graphitized fibers with high elastic modulus and low density are required. Particularly in aerospace and fishing rod applications where weight reduction effects are significant, lighter graphitized fibers are required to reduce weight as much as possible.

Conventional graphitized fibers have improved elastic modulus and higher density than high-strength carbon fibers, so even if the elastic modulus is improved, it is not reflected sufficiently in the specific elastic modulus, which is the actual problem. There was a problem. In particular, pitch-based graphitized fibers have a very high density of 2°0 g/cm3 or more, and even acrylic-based graphitized 1ilF-fibers have a density of 1.0 g/cm3 or more.
The specific elastic modulus was as high as 8 g/cm3 or more, and the specific elastic modulus was not sufficiently improved.

Therefore, the inventors first determined that the density was 1, 75. g/cm3
Low as below, and strength and elastic modulus of 650 each
kg/mm2 or more and 35 t/mm2 or more, high
In other words, the specific strength and specific modulus of elasticity are each 3.7×10
We have proposed a carbon fiber with a high thickness of 7 cm or more and 2.0XIO' cm or more (Japanese Patent Application No. 134032/1983), but the density is even lower and the elastic modulus is as high as 45 t/mm2 or more, so the specific modulus is very high. The present invention was achieved through extensive research into graphitized fibers.

[Problems to be Solved by the Invention] An object of the present invention is to provide a graphitized fiber that has a low density and a very high modulus of elasticity of 45 t/mm2 or more, which could not be achieved with the above-mentioned conventional techniques. There is a particular thing.

[Means for Solving the Problems] The above object of the present invention is to provide a low-density, high-elastic modulus graphitization characterized by having a density of 1.70 g/cm3 or less and a tensile modulus of 45 t/mm2 or more. This can be solved by fibers.

That is, the graphitized fiber of the present invention has a tensile modulus of 1,703 g/cm3 or less, preferably 1,65 g/cm3 or less, and a tensile modulus of 45 t/ml or more, preferably 50 t/cm3 or less.
mm2 or more, which simultaneously satisfies the level of physical properties that is extremely difficult with conventional technology, and has a specific modulus of elasticity of 2.
It is a graphitized fiber with a high elastic modulus and low density of 6 x 10' cm. Regarding the elastic modulus of graphitized fibers, acrylic graphitized fibers have recently achieved a high elastic modulus of 50 t/mm2 or more, and pitch-based graphitized A&I has a high elastic modulus of 70 t/mm2 or more.
A high elastic modulus of t/open 2 or higher has been achieved. However, in all cases, the higher the elastic modulus, the higher the density; therefore, a fiber with a high elastic modulus equals a fiber with a high density. Therefore, it is important for material developers and It was a structural designer's dream. Especially in space applications, 1 gram is said to be equivalent to more than 10,000 yen, and density is a very important point.

Note that the density in the present invention is a value measured according to the density measurement method specified in Jl5-R-7801, and the tensile modulus is a value determined by the resin-impregnated strand test method specified in Jl5-R-7601. be. That is, ″
Carbon fiber was impregnated with 100/3/4 parts of Bakelite "ERL-4221/Boron trifluoride monoengineered tylamine/acetone, and the resulting resin-impregnated strand was heated at 130°C for 30 minutes.
It was cured by heating for 0 minutes and determined by the resin-impregnated strand test method specified in J I 5-R-7601.

An example of the manufacturing method of the above-mentioned low-density, high-modulus graphitized m-fiber will be explained using an acrylic graphitized fiber as an example. That is, the acrylic polymer constituting the acrylic fiber (precursor), which is the raw material fiber of the acrylic graphitized fiber, contains at least 90 mol% or more of acrylonitrile and 1
0 mol% or less of copolymerizable vinyl monomers, such as acrylic acid, methacrylic acid, itaconic acid and their alkali metal salts, ammonium salts and lower alkyl esters, acrylamide and its derivatives, allylsulfonic acid, methallylsulfonic acid and copolymers with their salts or alkyl esters, but are not particularly limited.

Regarding the polymerization method, conventionally known solution polymerization, suspension polymerization, emulsion polymerization, etc. can be applied, but the degree of polymerization is 1.3 or more in terms of intrinsic viscosity ([η]).

Preferably it is 1.7 or more. That is, if the intrinsic viscosity ([η]) is less than 1.3, it is difficult to develop an elastic modulus, which is not preferable.

It is essential to add and mix one or more substances selected from polymers other than polyacrylonitrile, surfactants, and silicon compounds to the acrylic polymer. The amount added is 0.5% to 30% by weight.
is preferable, and more preferably from 2% to 10% by weight.
is within the range of If the amount added is less than 0.5% by weight, the effect of lowering the density is small, and if it exceeds 30% by weight, it tends to be difficult to develop an elastic modulus.

Additives include those that are compatible with the acrylic polymer so that they can be mixed uniformly, or those that do not contain metallic elements such as iron or sulfur, which would cause defects such as extremely large voids if added. is preferred.

Polymers include polyvinyl alcohol, polyacrylic acid, polyamide, and polyethylene oxide.

Examples include polymers such as polyimide, polypropylene, polyacrylamide, and polyethylene terephthalate, and examples of surfactants include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts,
Nonionic surfactants such as fatty acid ethylene oxide adducts, higher alkylamine ethylene oxide adducts, glycerol fatty acid esters, pentaerythritol fatty acid esters, or ionic surfactants such as lauryl alcohol sulfate sodium salt and trialkylammonium chloride. Medications can be given. Furthermore, silicon compounds include alkyl or aryl silicones such as dimethyl silicone, and modified polysiloxanes such as epoxy-modified and amino-modified polysiloxanes.

Addition methods include mechanical mixing using a stirring blade;
Alternatively, a method of adding the component dissolved in a solvent can be applied, but in either case, it is important to mix uniformly.

As the spinning method, a wet spinning method, a dry spinning method, a dry-wet spinning method, etc. can be employed, and a wet-dry spinning method is particularly preferred since it yields a highly dense precursor.

In order to obtain carbon a-fibers with high elastic modulus, a highly dense precursor is effective. Regarding the density, a dense precursor having a ΔL value of 30 or less, preferably 20 or less, more preferably 10 or less as measured by an iodine adsorption method is preferable.

Further, in order to obtain graphitized 11i fibers with high elastic modulus, a precursor with a high degree of orientation is preferable, and in particular, the degree of orientation (πaoo) determined by wide-angle X-ray diffraction is 85% or more, preferably 91
% or more is preferable.

To obtain acrylic fibers with an orientation degree (π400) of 85% or more as determined by wide-angle X-ray diffraction, coagulated fibers obtained by wet spinning or dry-wet spinning are subjected to hot water stretching, steam stretching, or glycerin. Stretching means such as stretching in a solvent can be applied.

The precursor single a fiber denier is 1.0d or less,
In particular, a fine denier of 0.8 d or less is preferable for improving the elastic modulus.

The flame-retardant conditions for firing such a precursor include a density of 1 to 3 in an oxidizing atmosphere at 240 to 300°C.
03/cm3 or more, preferably 1.35g1Cff13
Heating to a temperature above this level is effective in improving strength and elastic modulus. Also, at this time, the total stretching ratio was set to 1.0.
It is preferable to set it to 0 or more.

In particular, increasing the flame-resistant stretch ratio as the amount added is effective in improving the elastic modulus. As the atmosphere, a known oxidizing atmosphere such as air, oxygen, nitrogen dioxide, hydrogen chloride, etc. can be used, but air is preferable from the economic point of view.

In order to obtain a high elastic modulus, it is important that the maximum temperature at which the obtained flame-resistant fiber is fired in an inert atmosphere exceeds 2300°C, preferably 2500°C. Although the upper limit of the maximum temperature is not limited, it is preferable to set the maximum temperature in the range of 2300 to 2900° C., considering the life of the furnace material.

Furthermore, in the range of 2000℃ to maximum temperature, 1-40
%, preferably 5-35%, more preferably 10-3
It is important to perform 0% stretching in order to obtain a high elastic modulus.

In carrying out such a stretching process, the
Once the firing roller is passed through the outside of the furnace in the 000°C range, it is effective to increase the firing tension in the 2000°C to maximum temperature range, and is therefore effective in improving the elastic modulus.

Note that stretching by 3% or more, preferably 5% or more even in the range of 350 to 500°C is a preferable condition for obtaining a high elastic modulus.

As for the heating rate conditions, the heating rate in the temperature range of 350 to 500°C should be 500°C/min or less, preferably 200°C/min.
It is effective to improve the stretchability and prevent the occurrence of fluff by setting the temperature increase rate from 2000° C. to the maximum temperature to 1000° C./min or less, preferably 500° C./min or less. In addition, the temperature increase rate in the temperature range of 500 to 2000°C should be set to 500°C/min or more, preferably 700°C.
/min or more is effective in reducing the density of graphitized yarn.

As described above, examples of the method for manufacturing the fiber of the present invention include specifying the polymer, precursor 2 spinning, flame resistance, carbonization, and graphitization conditions. These techniques can also be applied to other graphitized a#a such as pitch-based graphitization.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, the degree of orientation (π400) of the precursor according to the present invention is determined by ΔL determined by the iodine adsorption method and by wide-angle X-ray diffraction.
are the values obtained by the following methods.

ΔL by iodine adsorption method Approximately 0.5 g of a dry sample with a fiber length of 5 to 7 cm was accurately weighed, and 20
Pour into a 0ml Erlenmeyer flask with a stopper, add iodine solution (I2: 51g, 2.4-dichlorophenol 10
Weigh out 90 g of acetic acid, 90 g of potassium iodide, transfer to a volumetric flask No. 11, dissolve with water to make a constant volume), add 100 ml, and perform adsorption treatment while shaking at 60° C. for 50 minutes. The iodine-adsorbed sample was placed in running water for 3 minutes.
After washing with water for 0 minutes, centrifugal dehydration (2000 rpm x 1 minute) and quick air drying. After opening this sample, the lightness (L value) is measured using a Hunter type color difference meter [Model CM-25, manufactured by Color Machine Co., Ltd.] (L,).

On the other hand, a corresponding sample without iodine adsorption treatment was opened, and the lightness (LO) was similarly measured using the Hunter type color difference meter, and the lightness difference ΔL was determined from Lo L+.

Orientation degree by wide-angle X-ray diffraction (π400) N as an X-ray source
Using α rays on Cu that has been monochromated with an i filter,
Plane index observed around θ = 17.0° (400)
From the half-width H (°) of the peak obtained by scanning the peak in the circumferential direction, π4oo=((180-H)/18
0) X100 (%).

Examples 1-5. Comparative Example 1 Using a copolymer consisting of 99.4 mol% acrylonitrile (AN) and 0.6 mol% methacrylic acid, the concentration was 20%.
A wt % dimethyl sulfoxide (DMSO) solution was prepared. The additives shown in Table 1 were added to this solution, mixed thoroughly using a stirring blade, the temperature was adjusted to 35°C, and the pore size was 0.
Once discharged into the air through a 12 mm, 3000 hole spinneret and run through a space of about 6 mm, the temperature was 5°C.
.

It was coagulated in an aqueous DMSO solution with a concentration of 30%. After washing the coagulated yarn with water, it was stretched 3.5 times in a three-stage hot water stretching bath, and a silicone oil was applied thereto, and then it was brought into contact with a roller surface heated to 130 to 160°C to be dried and densified.
7, the fiber bundle was drawn three times in the pressurized steam of GLCL112 to obtain a fiber bundle with a single yarn fineness of 0.8 d and a)-taldenier 2400 D. The obtained acrylic fiber had a ΔL of 18. The degree of orientation (π400) by wide-angle X-ray diffraction is 86-92
% range.

The obtained fiber bundle was heated in air at 240 to 280°C under conditions such that the total drawing ratio was as shown in Table 1, and the density was 1,
It was converted into flame resistant fiber of 36 g/cm3. Then 350
After stretching by 8% at a heating rate of 200°C/min in the temperature range of ~500°C, the film was fired at 900°C via a drive roller outside the furnace and then further fired to 1800°C. 90
The temperature increase rate in the 0 to 1800°C region is 600°C/min,
A 1% shrinkage was performed. Furthermore, it is heated at 2000 to 200°C in a nitrogen atmosphere at a maximum temperature of 2600°C via a drive roller outside the furnace.
The heating rate in the 600° C. region was 500° C./min, and 10% stretching was performed in this region to obtain a graphitized fiber. Table 1 shows the properties of the graphitized fibers obtained.

Examples 6-7. Comparative Examples 2 to 3 Graphitized fibers were obtained by graphitizing under the same conditions as in Example 1 except that the maximum graphitization temperature and the stretching ratio from 2000° C. to the maximum temperature were changed as shown in Table 2. Table 2 shows the properties of the graphitized fibers obtained.

(The following is a margin) [Effect of the invention] The graphitized wA fiber of the present invention has a density of 1.70 g/cm
3 or less, has a high tensile modulus of 45 t/mm2 or more, and has a specific modulus of 2.6 x 10' am, making it a low-density, high-modulus fiber that can be used to make aerospace materials and sports materials such as fishing rods lighter and more This makes it possible to make the graphitized fibers thinner, further expanding the scope of use of graphitized fibers.

Claims (1)

[Claims] A low-density, high-modulus graphitized fiber having a density of 1.70 g/cm^3 or less and a tensile modulus of 45 t/mm^2 or more.