JPH0378414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an aggregate of acrylonitrile-based carbonaceous reinforcement fibers having high strand strength, low specific gravity, and strand modulus close to that of glass fibers. This is a reinforcing fiber material that is highly flexible and suitable for molding lightweight molded products.

[Background technology]

In recent years, carbon fibers with a carbon content of 95% or more have been
Because it has high strength, high elastic modulus, and specific gravity of 1.6 to 1.9, it is mainly used in composites with various matrix materials, such as thermosetting or thermoplastic plastics, in the form of fiber bundles (strands) or chops. It is widely used in the fields of aircraft, automobiles, and sporting goods.

However, carbon fibers, which are normally manufactured using acrylic fibers as precursors, suffer a weight loss of 45 to 50% during carbonization, and in addition, the firing temperature is over 1000°C, so the raw material It is an expensive product because of the high cost, energy cost, and the need for a high-temperature furnace of 1000℃ or more and special high-temperature heat-resistant materials used in it, which also increases equipment costs. Ta. Although carbon fiber is expensive, it is a physically superior material with high strength and elasticity and a lower specific gravity than glass fiber, so it is often used in fields where quality is a priority. It's here.

[Problems with conventional technology]

However, since such carbon fibers have a high modulus of elasticity, they are too hard and unsuitable for use in lightweight, soft sports equipment such as women's golf club shafts and tennis rackets.

In other words, when molding these using carbon fiber as a reinforcing material, the molding is usually done through prepreg, but when manufacturing prepreg, the fiber basis weight is at most 10 g/ ^m2 , and such ultra-thin materials It is not easy to manufacture prepregs from the viewpoint of quality control, and the productivity is extremely low. In addition, it has poor handling properties during molding.

Prepreg fibers with a basis weight of 50 to 200g/ ^m2 are easiest to handle and have high productivity, but if carbon fiber is used as prepreg with such a basis weight and molded products are manufactured, the above problems will occur. .

As a reinforcing material for manufacturing such molded products,
It is conceivable to use glass fiber alone or to use glass fiber and carbon fiber in combination, but if this is done, the molded product will become heavy and cannot withstand long-term play.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned drawbacks of carbon fiber and to provide a fiber that has an elastic modulus close to that of glass fiber and aromatic polyamide fiber, but also has the characteristics of conventional carbon fiber. , thereby developing new uses for carbon fiber.

[Structure of the invention]

The present invention is as follows.

Carbon number content 70-90% by weight, strand strength
250Kgf/mm2 or ^more , strand elastic modulus 13000Kgf/
An aggregate of acrylonitrile-based carbonaceous reinforcing fibers with a size of mm ² or more and less than 18000 Kgf/mm ² .

Such acrylonitrile-based carbonaceous reinforcement fiber aggregates have high productivity when made into prepregs, do not need to be made into prepregs with ultra-low fiber weight, and can be selectively used in combination with scrim cloth, which improves flexibility. It is a reinforcing fiber material suitable for molding tall and lightweight molded products.

In the present invention, the acrylonitrile-based carbonaceous reinforcement fiber is a reinforcing fiber material derived from acrylonitrile-based fiber, and the acrylonitrile-based fiber contains at least 93% by weight of acrylonitrile.
It is a fiber obtained by spinning a polymer contained as a polymer component by a known method.

Aggregates here refer to fiber bundles, sheets, fabrics,
Nonwoven fabrics, paper, etc.

The matrix resin used in the preferred usage example of the present invention includes common resins used as matrix resins for fiber-reinforced composite materials, such as unsaturated polyester resins, phenolic resins,
Epoxy resins and the like are particularly preferred as the matrix resin, since the acrylonitrile-based carbonaceous reinforcing fibers of the present invention have high water absorption.

As the curing agent, known curing agents that are compatible with each matrix resin can be used.

As curing agent components of the epoxy resin, dicyandiamide, imidazole compounds, polyamide compounds, acid anhydride curing agents, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, etc. are used.

In particular, for epoxy resin systems, phenol and
Single or mixed resins such as novolak type epoxy resin, bisphenol A type epoxy resin, and modified resins thereof are used. As a third component, a viscosity modifier (for example, an inorganic filler such as fine silica powder),
Nitrile rubber and the like can also be used. Examples of preferred specific blending ratios of these resin compositions are as follows.

Phenol/novolac type epoxy resin 50~80
Weight% and bisphenol A type epoxy resin 50-80
dicyandiamide, 3-(3,4
-dichlorophenyl)-1,1-dimethylurea (0.5 to 6 parts by weight), and if necessary, a viscosity modifier is added, so that the viscosity after blending is
It is preferable to adjust the temperature to 30 to 300 poise (80°C).

In order to impregnate the acrylonitrile-based carbonaceous reinforcing fiber aggregate with the resin composition, known methods such as a solvent method and a hot melt method are employed.

The appropriate ratio of the acrylonitrile-based carbonaceous reinforcing fiber aggregate to the matrix resin is 25 to 50% by weight based on the resin content. The fiber content when formed into a molded product is preferably 30 to 60% by volume.

The acrylonitrile-based carbonaceous reinforcing fiber aggregate of the present invention is suitable for use as a reinforcing fiber as long as it is, but it can also be used as a cut fiber as a reinforcing fiber for a thermoplastic resin, or mixed with an appropriate amount of pulp and used as a reinforcing fiber. It can also be used as a sheet-like molded product by impregnating and curing it.

In the present invention, the carbon content must be 70 to 90% by weight. If the carbon content is lower than 70% by weight, the water absorption of the fibers will increase, making it difficult to select a suitable matrix resin, and the performance of the composite material will also deteriorate. If the carbon content is less than 90% by weight,
Because it has excellent adhesion with resin, it does not require surface treatment like that used for ordinary carbon fibers, but if it exceeds 90% by weight, the adhesion with resin decreases and surface treatment is necessary. occurs.

Strand strength is 250Kgf/mm ² or more. If the strand strength is less than 250 Kgf/mm ² , the strength is low, and in order to achieve the desired performance, the composite material must be thick, which increases the weight of the molded product.

Strand elastic modulus is 13000Kgf/ ^mm2 or more 18000/
Less than ^mm2 . Strand elastic modulus is 13000Kgf/
If it is less than mm ² , the elastic modulus will be too low and the weight of the molded product will increase. On the contrary, 18000Kg
If it exceeds f/mm ² , an extremely thin prepreg must be made in order to reduce the amount of reinforcing material used in the molded product, which does not solve the problem mentioned at the beginning.

The above-mentioned reinforcing fibers are derived from acrylonitrile fibers. In general, carbon fibers include rayon-based, pitch-based, acrylonitrile-based, etc., but in the case of pitch-based, the elastic modulus is 17000 kg
f/mm ² , the strength is only about 170 Kgf/mm ² at most, and it is difficult to obtain reinforcing fibers with the balance of the present invention. In the case of rayon, the strength is even lower. However, when derived from acrylonitrile fibers, reinforcing fibers with this balance can be easily obtained.

〔Effect of the invention〕

Conventionally known carbon fibers have a carbon content of more than 95% by weight, but the acrylonitrile-based carbonaceous reinforcement fibers constituting the aggregate of the present invention have a carbon content far greater than that of carbon fibers. It is lower than that of flame-resistant fibers and their precursor acrylonitrile fibers.

The acrylonitrile-based carbonaceous reinforcement fiber of the present invention has performance comparable to conventional carbon fiber in terms of strand strength and fiber specific gravity, and has a strand elastic modulus that is close to or slightly higher than glass fiber or aromatic polyamide fiber. It is a reinforcement fiber with a value.

The performance of the acrylonitrile-based carbonaceous reinforcing fiber of the present invention is as follows.

Strand strength: 250Kgf/ ^mm2 or more Strand elastic modulus: 13000Kgf/ ^mm2 or more 18000Kg
Less than f/mm ² Carbon content: 70-90% by weight Specific gravity: 1.6-1.9 Composite tensile strength: 100Kgf/mm ² or more (converted to Vf60 volume%) Composite tensile modulus: 5000Kgf/mm ² or more (Vf60 volume%) Conversion) As described above, the specific gravity of the present invention is much lower than that of glass fiber, and the elastic modulus is close to that of glass fiber.
Moreover, it is a reinforcing fiber with a unique balance of strength and performance compared to carbon fiber.

The acrylonitrile-based carbonaceous reinforcing fiber of the present invention can be obtained as follows. Acrylonitrile fiber is a fiber obtained by copolymerizing 93% by weight or more of acrylonitrile with a known comonomer that can be copolymerized.In particular, the comonomer includes 1 to 5% by weight of methyl acrylate, sodium methallylsulfonate, etc. 0.1-0.5% by weight, or itaconic acid 0.5-
Molecular weight consisting of 1.5% by weight of selected components
A fiber bundle of 30,000 to 100,000, a molecular orientation degree of 85% or more, a single fiber denier of 0.1 to 1.0, and 100 to 100,000 fibers is preferable. Flame resistance is achieved by heating the acrylonitrile fiber bundle in an oxidizing atmosphere, mainly air, in a flame resistance furnace equipped with a multi-stage roller group, at a temperature of 10°C above the decomposition temperature of the fibers.
The specific gravity of the fibers is adjusted to 1.33 to 1.40 by continuously passing the fibers under tension while gradually increasing the temperature by ~60°C. In particular, in order to obtain the reinforcing fibers of the present invention,
It is preferable to make the acrylonitrile fiber flame resistant by applying tension and temperature so that the degree of orientation at the X-ray diffraction angle 2θ = 17° is maintained at 80% or more when made into a flame resistant fiber.
Tension is applied to fibers with an orientation degree of 88% or more at =17°,
It is more preferable to achieve flame resistance at 100 to 300 mg/d. When the tension is less than 100 mg/d, the elastic modulus of the carbonaceous fiber obtained is low;
If it exceeds this, the carbonaceous fibers will have an extremely large amount of fuzz, which tends to cause problems in terms of the required quality of the bundle.

Regarding the flame resistance temperature, it is appropriate to increase the temperature in stages so that the reaction between the fiber and oxygen associated with flame resistance and the cyclization reaction of the nitrile groups in the fiber occur uniformly on the cross section of the fiber. It is. Preferably, the start temperature is 10 to 60°C lower than the decomposition temperature of the acrylonitrile fiber in air, and the temperature is lower than the decomposition temperature.
It is preferable to raise the temperature stepwise to a temperature 20 to 30°C lower.

It is appropriate that the flame resistance time is 0.3 to 1 hour so that the specific gravity of the flame resistant fiber is 1.33 to 1.40.
When the specific gravity of the flame-resistant fiber is less than 1.33, the weight percent (carbonization rate) of the obtained carbonaceous fiber based on the weight of the precursor fiber becomes extremely small, which is not preferable. Further, when the specific gravity exceeds 1.40, the strength of the obtained carbonaceous fiber tends to decrease. An example of a flame-resistant furnace used to obtain the reinforcing fiber of the present invention is a furnace having a multi-stage roller group as shown in Fig. 1, and the inside of the furnace is divided into at least two chambers, each having a temperature It has a structure that can be adjusted, and has a structure in which the fibers are continuously supplied into the furnace from the supply roller Rfp, made flame resistant, and finally taken off by the roller Rfp. Fire-resistant fibers are fired at temperatures of 750 to 1000°C in an atmosphere of nitrogen, argon, etc.
Usually, the process is carried out by continuously passing the fiber through a furnace as shown in FIG.

If the firing temperature is less than 750℃, the strand strength,
This is not preferable because the strand elastic modulus becomes low.
Moreover, if the temperature exceeds 1000°C, the elasticity becomes too high and the purpose is not achieved. . The baking time is
It depends on the temperature, and if the temperature is high, it is preferable to shorten it, but usually 0.5 to 10 minutes is appropriate. When the time is less than 0.5 minutes, the strand elastic modulus tends to decrease. If the time exceeds 10 minutes, energy costs tend to increase.

In particular, in order to obtain the reinforcing fiber of the present invention, it is preferable to apply a tension of 150 mg/d to 250 mg/d during firing. If it is less than 150 mg/d, the strand strength and strand elastic modulus are low;
If it exceeds d, the resulting fibers tend to have a lot of fluff and are of poor quality.

Normally, when the specific gravity of the flame-resistant fiber is 1.33 to 1.40, it is desirable that the tension during firing is 150 to 250 mg/d, and the tension is increased according to the specific gravity of the flame-resistant fiber.

Figure 2 shows the supply roller Rfc, the furnace core tube 2, the furnace body 3, the heat insulator 4, the heater 5, and the take-up roller.
In this firing furnace, the fiber 1 passes through the roller Rfc and inside the furnace core cylinder, and is continuously fired so as to be taken up by the roller Rtc.

Example 1 A polymer (molecular weight: 65,000) consisting of 96% by weight of acrylonitrile, 1% by weight of itaconic acid, and 3% by weight of methyl acrylate had a degree of orientation of 88% at 2θ=17° in air. Acrylonitrile fiber bundles (single fibers of 0.8 denier, 12,000 fibers) with a decomposition temperature of 287°C were placed in the flameproofing furnace shown in Figure 1.
After passing through the supply roller Rfp, it was processed in a first zone at a furnace temperature of 250° C. for 30 minutes and a second zone at a furnace temperature of 263° C. for 24 minutes, and then continuously taken off by a take-off roller Rtp.

During flame resistance, the tension applied to the fibers at each roller portion was 105 mg/d, and the degree of X-ray orientation at 2θ=17° of the flame resistant fibers finally obtained was 81%.
In addition, optical microscopic observation was performed on the fibers of the same roller sections, and it was confirmed that the degree of development of the black portion in the cross section of the fibers was uniform, and that the flame resistance reaction was occurring uniformly. The specific gravity of the obtained flame-resistant fiber bundle was 1.35. This flame-resistant fiber bundle was introduced into the firing furnace shown in Fig. 2 with an inlet temperature of 330°C and a maximum temperature inside the furnace of 930°C, and was taken off by a take-off roller Rtc for 3 minutes at the maximum temperature.

The tension during firing was set to 180 mg/d between the supply roller Rfc and the take-off roller Rtc. The strand performance of the obtained acrylonitrile carbonaceous fiber was as follows.

Carbon content: 89% by weight Strand strength: 300 Kgf/mm ² Strand elastic modulus: 17200 Kgf/mm ² Example 2 (Usage example) Acrylonitrile carbonaceous fibers were obtained in the same manner as in Example 1. A unidirectionally arranged sheet of this material was impregnated with the following resin solution, and the solvent was removed by heating and drying at 90 to 100°C, resulting in a fiber area weight of 150 g/m ² and a resin content of
A unidirectional prepreg of 38% by weight was obtained.

Using this unidirectional prepreg, 130℃, 7Kg/
The physical properties of the molded product molded under curing conditions of cm ² 90 minutes are as follows:
It was as follows.

Bending strength: 145 Kgf/mm ² Flexural modulus: 10800 Kgf/mm ² Layer shear strength (room temperature): 10.1 Kgf/mm ² (ILSS) Vf: 60% by volume [Resin solution] Phenol-novolac type epoxy resin (Araldite manufactured by Ciba Geigy) EPN1138) 70 parts by weight,
Bisphenol A type epoxy resin (20 parts by weight of Epicoat 1002 manufactured by Ciel Chemical Co., Ltd., Epicoat 828 manufactured by Ciel Chemical Co., Ltd.)
A resin mixture (100 poise, 80° C.) was prepared by mixing 30 parts by weight of a mixture system consisting of 10 parts by weight. To this, 3 parts by weight of the curing agent dicyandiamide and 3 parts of the curing accelerator.
(3.4dichlorophenyl)-1.1-N dimethylurea 5
Add 40 parts by weight and dissolve in a 1:1 mixed solvent of acetone and ethylene glycol monomethyl ether.
It was made into a weight% resin solution.

Example 3 The maximum temperature inside the firing furnace in Example 1 was set to 780
Acrylonitrile-based carbon fibers having the following performance were obtained in the same manner as in Example 1 except that the temperature was changed to .degree.

Carbon content: 78% by weight Strength: 255 Kgf/mm ² Modulus of elasticity: 13500 Kgf/mm ² Example 4 (Usage example) The same resin composition as in Example 2 was prepared using the acrylonitrile carbonaceous fiber obtained in Example 3. It was made into prepreg. The physical properties of a molded product made from this material were as follows.

Bending strength: 110Kgf/mm ² Bending modulus: 11400Kgf/mm ² LISS (room temperature): 9.5Kgf/mm ² Vf: 60% by volume

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the flameproofing device, and FIG. 2 is a schematic diagram of the firing furnace. In the figure, each symbol is as follows. A: Flame resistant furnace first zone, B: Flame resistant furnace second zone, C: Flame resistant furnace partition wall, Rfp, Rfc: supply rollers, respectively, Rtp, Rtc: take-up rollers, respectively, 1: fiber, 2: furnace core Cylinder, 3: Furnace body, 4:
Insulating material, 5: heater, 6: sealing material, 7: inert gas supply port.

Claims (1)

[Claims] 1 Carbon content 70-90% by weight, strand strength
250Kgf/mm2 or ^more , strand elastic modulus 13000Kgf/
An aggregate of acrylonitrile-based carbonaceous reinforcing fibers with a size of mm ² or more and less than 18000 Kgf/mm ² .