JPH09249747A - Silicone rubber, silicone rubber particle, precursor for carbon fiber, and carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain silicone rubber particles having a small size which could not been easily obtained in the prior art and which are usable for producing carbon fibers of a high strength. SOLUTION: Substantially spherical silicone rubber particles having an average diameter of not larger than 1μm are obtained by curing an uncured silicone containing an amino-modified silicone or/and an epoxymodified silicone by irradiation with electron beams. The silicone rubber particles are attached to the surfaces of fibers to obtain a precursor for carbon fibers, and this precursor is burned to obtain carbon fibers having a high strength.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to silicone rubber particles and high-strength carbon fibers to which they are applied, and more specifically, silicone rubber, silicone rubber fine particles and a method for producing the same, a silicone rubber dispersion, and further , A precursor for carbon fiber to which silicone rubber particles are applied, and a carbon fiber.

[0002]

2. Description of the Related Art Silicone rubber is a silicone elastomer excellent in low compression set, high impact resilience and releasability in addition to its characteristics as silicone in terms of heat resistance, cold resistance, weather resistance, electrical characteristics and the like. It also has characteristics such as characteristics and high oil absorption. Conventionally, taking advantage of these characteristics, silicone rubber is added to synthetic resins and rubbers to impart heat and cold resistance, slipperiness and anti-adhesion properties, and addition to cosmetics, polishes, paints, inks and papers. Is also being done.

The present inventors have previously proposed that when fine particles of silicone rubber are applied to a precursor for carbon fiber, the adhesion between single yarns during heat treatment is suppressed and a carbon fiber having high strength can be easily obtained. (Japanese Patent Application No. 7-191672
issue). As a method for producing the silicone rubber fine particles,
If the particles are of an irregular type, there is a method of mechanically crushing the silicone rubber cured by the curing reaction.For particles of a spherical type, the silicone rubber before the curing reaction is dispersed in fine particles in a medium such as water. A method of heat curing as it is,
There is a method of spraying the dispersion in high temperature air to cure it. However, the mechanical pulverization method has the drawback that only irregularly shaped particles can be obtained and the particle size distribution is quite wide, and it is difficult to obtain small particles having an average particle size of 1 μm or less. In addition, spherical silicone rubber fine particles can be obtained by a method of heat-curing a silicone dispersion liquid. However, in this method, a silicone group is hardened by heat or the like. The situation was that it could only be applied to silicones contained as. for that reason,
Those having a small dispersion diameter before curing cannot be obtained, and as a result, it is very difficult to obtain fine particles having an average particle diameter of 1 μm or less. Furthermore, by the method of spraying in high temperature air to cure, mechanical pulverization method, etc., only dry rubber fine particles can be obtained, and it is very difficult to disperse it in the liquid. It is not possible to meet the demands in the fields where liquids are required.

[0004]

The object of the present invention is to facilitate the provision of silicone rubber particles having a small average particle diameter and a dispersion thereof, which has been difficult to achieve in the above-mentioned prior art, and further to apply the silicone rubber particles. The present invention provides a precursor for carbon fiber and a high-strength carbon fiber.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above problems. First, the silicone rubber of the present invention is basically obtained by irradiating an uncured silicone with an electron beam to cure it. It is a thing. The silicone rubber particles of the present invention are obtained by irradiating an uncured silicone with an electron beam to granulate the silicone rubber, and the silicone constituting the silicone rubber and the silicone rubber particles is preferably an amino-modified silicone or / And epoxy-modified silicone. Furthermore, the silicone rubber particles of the present invention preferably have a substantially spherical shape, and the present invention includes fine particles having an average particle diameter of 1 μm or less. And, as one of the embodiments, these silicone rubber particles of the present invention can be dispersed in a liquid and used in the state of a dispersion liquid. The silicone concentration in this silicone dispersion is preferably 5% by weight or more.

Next, the silicone rubber particles of the present invention can be produced by irradiating an uncured silicone, preferably a dispersion liquid containing silicone, with an electron beam for granulation. In this case, the total irradiation dose of the electron beam is preferably 50 kGy or more, and
Irradiation with an electron beam from a plurality of times and / or a plurality of directions is included as a preferred embodiment. In this case, the irradiation dose of the electron beam per irradiation is preferably 10 to 500 kGy. Furthermore, as an embodiment of the present invention, the minimum value with respect to the maximum value of the absorbed dose of electron beams is 0.4 or more.

The silicone rubber particles of the present invention are preferably used to obtain high-strength carbon fibers. That is, the carbon fiber of the present invention, first, on the surface of the raw material fiber, a precursor for carbon fiber having silicone rubber particles on the fiber surface by adhering the particulate silicone rubber,
This precursor for carbon fiber can be fired at a high temperature to obtain high-strength carbon fiber.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below.

In the present invention, silicone means a compound having a siloxane bond (--SiO--) in the basic skeleton, and the group bonded to the silicon atom is a hydrogen atom or / and an alkyl group having 1 to 3 carbon atoms. And phenyl groups, or alkoxy groups thereof. Of these, dimethylsiloxane is particularly preferable as the basic skeleton. In the present invention, the silicone rubber generally means a rubber obtained by vulcanizing and curing the above silicone.

The shape of the silicone rubber particles in the present invention is preferably spherical. The intention of forming a spherical shape is that, for example, when silicone rubber particles are mixed with a resin and applied, if the shape is not a spherical shape, the viscosity of the resin may greatly increase. When applied to, if the particles have sharp corners, the precursor may be scratched and the strength may be reduced.

The term "spherical shape" as used herein means that the maximum diameter and the minimum diameter of each of arbitrary 50 particles are measured by SEM, and the average of 50 ratios (maximum diameter / minimum diameter) is in the range of 1 to 2. The average of this ratio is 1 to
It is preferably 1.5, more preferably 1 to 1.3, and further preferably 1 to 1.1.

In the present invention, the average particle size of the silicone particles can be defined as follows. That is, S
The maximum diameter and the minimum diameter of each arbitrary 50 particles are measured by EM, and the average thereof is calculated as the particle diameter, and the average of the 50 particles is calculated. The SEM observation conditions are as follows.

Sample mount: A cover glass on which silicone rubber fine particles are placed is attached to a sample table with a carbon adhesive tape.

-Sample coating: platinum-palladium-Acceleration voltage: 20 kV-Emission current: 10 μA-Working distance: 15 mm When the silicone rubber particles are applied to the precursor for carbon fiber in the practice of the present invention, the particle diameter of the silicone rubber particles Is smaller, the more preferable. Specifically, it is preferable that the average particle size of the particles is 1 μm or less, and
The thickness is more preferably 5 μm or less, further preferably 0.3 μm or less.

If the particle size of the silicone rubber particles is too large, it becomes difficult for the particles to form a gap between the single yarns of the precursor for carbon fiber and to control the adhesion between the single yarns during the heat treatment of the precursor.

In the present invention, the silicone is cured by electron beam, but the silicone used is not limited to the silicone having a vinyl modifying group. As the type of silicone, those having a methyl group or a phenyl group as a side chain in the structural unit are mainly used, but unmodified, amino-modified, amide-modified, epoxy-modified, carboxyl-modified, carbinol-modified, Silicones such as mercapto-modified, phenol-modified, methacryl-modified, vinyl-modified, polyether-modified, alkyl-modified with 2 or more carbon atoms and fluoroalkyl-modified can be used. These modifying groups can be placed on the side chains or terminals, and conventionally curable silicones can also be used. Further, two or more kinds of these silicones may be combined, or a silicone having two or more kinds of these modifying groups in one molecule may be used.

The silicone rubber particles may be required to have affinity or reactivity with a resin or rubber added or added, and it is preferable to use silicone having an amino-modified group and / or an epoxy-modified group. When added to a resin or rubber, there is an advantage that these functional groups react to increase adhesion, and when added to a fiber, it is easily adsorbed. Further, various functional groups can be provided on the surface of the particles if necessary.

In the present invention, 2 of uncured silicone is used.
The kinematic viscosity at 5 ° C. is 10 × 10 ⁻⁶ m ² / s to 200.
It is preferably 00 × 10 ⁻⁶ m ² / s, 30 × 1
More preferably ^{0 -6 m 2 / s~18000 × 10} -6 m 2 / s, 50 × 10 -6 m 2 / s~15000 × 1
More preferably, it is 0 ^-6 m ² / s. If the kinematic viscosity is low, the flash point may be low, and if the kinematic viscosity is too high, it may be difficult to disperse it in a liquid, especially water.

In the present invention, amino-modified silicone and / or epoxy-modified silicone can be used as the silicone. The ratio of amino groups to amino groups and epoxy groups is preferably 0.01 to 0.99, and 0.1 to 0.
9 is more preferable, and 0.3-0.7 is still more preferable.

When the amino-modified silicone is used, it may be a monoamine type or a polyamine type. The modification amount in which the terminal amino group is converted to —NH ₂ is preferably 0.05 to 10% by weight, more preferably 0.1 to 5% by weight.
If it is less than 0.05% by weight, a resin to be added or added,
The affinity for rubber and the like may be insufficient, and if it exceeds 10% by weight, the heat resistance may decrease. Moreover, the kinematic viscosity at 25 ° C. is 250 × 10 ⁻⁶ m ² / s to 1000.
It is preferably 0 × 10 ⁻⁶ m ² / s, 500 × 1
^{0 -6 m 2 / s~8000 × 10} -6 m 2 / s is more preferable. If it is less than 250 × 10 ^-6 m ² / s, the heat resistance may be insufficient, and 10000 × 10 ^-6 m ² / s × 10 ^-6 m ² /
If it exceeds s, it may be difficult to disperse it in a liquid, especially water.

When the epoxy-modified silicone is used, it may be an ether type or an alicyclic epoxy-modified type such as a 1,2-epoxycyclohexyl group or a 1,2-epoxycyclopentyl group. An epoxy group -CHCH ₂ O
The modified amount converted into is preferably 0.05 to 10% by weight, and more preferably 0.1 to 5% by weight. 0.05
If it is less than 10% by weight, the affinity for the added or added resin, rubber, etc. may be insufficient, and if it exceeds 10% by weight, the heat resistance may be lowered. Moreover, the kinematic viscosity at 25 ° C. is 1000 × 10 ⁻⁶ m ² / s to 15000 × 10.
^-6 m ² / s is preferable, 2000-1200
0 × 10 ⁻⁶ m ² / s is more preferable. 1000 x 10 ^-6
If it is less than m ² / s, the heat resistance may be insufficient,
00 × 10 ^- exceeding ⁶ m ² / s when the liquid, it may be difficult, especially to disperse in water.

One of the methods for producing the silicone rubber particles in the present invention is a method of curing the silicone rubber with an electron beam.

The irradiation dose can be selected depending on the hardness of the desired silicone rubber, but the irradiation dose is set to 50 for curing.
kGy or more is preferable, 100 kGy or more is more preferable, and 300 kGy or more is further preferable. However, if the dose is too high, heat may be generated or the silicone may deteriorate due to decomposition by an electron beam, and it may be difficult to irradiate a high dose industrially. Therefore, it is preferable to keep the dose below 10 MGy. .

If the accelerating voltage of the electron beam is too low, the penetrating power is too small to provide uniform treatment, and if it is too high, it is generally difficult to obtain.
MV is preferable, 150 kV to 5 MV is more preferable,
200 kV to 1 MV is more preferable.

In the practice of the present invention, in order to ensure the uniformity of processing, it is preferable to irradiate the electron beam with the object to be irradiated having a small thickness. Specifically, considering the specific gravity of the irradiated body in the depth dose curve at a predetermined acceleration voltage, it is preferable to set the thickness so that the absorbed dose on the opposite side of irradiation is 40% or more of the maximum value, and 50% or more. Is more preferable, and 60% or more is further preferable. Also,
From this point of view, it is preferable to perform irradiation from a plurality of directions such as two directions, instead of irradiation from only one direction, because the processing thickness can be increased while maintaining the processing uniformity. In that case, it is preferable to set the thickness so that the absorbed dose in the central portion of the irradiation liquid in the thickness direction is 40% or more of the maximum value, more preferably 50% or more, and further preferably 60% or more.

In the present invention, it is also possible to irradiate an uncured silicone with an electron beam to cure the silicone rubber, and then pulverize it to obtain amorphous fine particles. However, in order to obtain spherical fine particles, the uncured silicone is uncured. It is preferable to irradiate the dispersion liquid obtained by dispersing the above silicone in a liquid with an electron beam. In this case, any liquid can be used as long as it can disperse silicone, but it is preferable to use water from the viewpoint of safety, low toxicity, handleability and the like. In the dispersion liquid, it is preferable to select and use a surfactant if necessary according to a conventional method. Since the higher the silicone concentration in the dispersion liquid is, the higher the production efficiency of electron beam irradiation is, the silicone concentration is preferably 5% by weight or more, unless the stability of the dispersion liquid before and after irradiation is problematic. More preferably, it is more preferably 15% by weight or more. Also, if the irradiation dose per dose is too high, the dispersion of silicone may be destroyed by the temperature rise, so it is preferable that the irradiation dose per dose is low, but if it is too low, the production efficiency of electron beam irradiation will decrease. Therefore, the irradiation dose per irradiation is preferably 10 to 500 kGy, more preferably 30 to 300 kGy, and 50 to 1
00kGy is more preferable. When the electron beam is irradiated in two or more times, it is preferable to cool the silicone dispersion liquid whose temperature has increased during the irradiation with air, water or the like.

The silicone rubber particles of the present invention can be secondarily cured by a known method including electron beam in the dispersion or after drying.

Next, the precursor for carbon fiber having the silicone rubber particles of the present invention on the fiber surface will be described.

Since carbon fibers have excellent specific strength and specific elastic modulus as compared with other fibers, they are widely used industrially as reinforcing fibers for composite materials with resins by utilizing their excellent mechanical properties. ing. In recent years, the superiority of the carbon fiber composite material has been further increased, and particularly in sports and aerospace applications, there is a strong demand for high performance of the carbon fiber composite material. The properties of the composite material largely depend on the properties of the carbon fiber itself, and this demand is, of course, a demand for higher performance of the carbon fiber itself.

In order to produce such a high-performance carbon fiber, it is necessary to suppress the generation of defects which are particularly the starting points of fracture. In particular, most of the carbon fiber fractures occur from the surface, and it can be seen that the contribution of surface defects is large. The causes of such surface defects are:
The adhesion of foreign matter, the generation of scratches by rollers, etc., the bonding between single yarns due to heat, etc. can be mentioned. It has been found that the carbon fiber having a higher strength level can be obtained by applying the silicone rubber fine particles of the present invention to the precursor for use in the present invention.

The precursor for producing carbon fiber of the present invention is
Since the surface has the silicone rubber particles, the particles enter into the space between the single yarns and the direct contact between the single yarns is suppressed, so that high-strength carbon fibers can be obtained. Even with the same particulates, inorganic particulates such as silica, alumina, and metals are generally hard and easy to damage the precursor, and the metal forms carbides to create defects, whereas silicone rubber particles do not. High-strength carbon fiber can be obtained.

Further, among the silicone particles, if it is too hard, it may damage the precursor, and if it is too soft, it may be deformed by the tension during the process and the effect of suppressing the adhesion between single yarns may be reduced, so that it is appropriate. It preferably has hardness.

If the particles in the present invention contain a metal, they may react with the precursor during carbonization to form a carbide to reduce the strength. Therefore, it is preferable that the particles do not contain a metal. 1000pp as total metal content
m or less is preferable, 100 ppm or less is more preferable,
10 ppm or less is more preferable, and it is preferable that no metal is ideally contained.

If the amount of silicone particles deposited on the precursor of the present invention is too small, the effect will be poor, and if it is too large, contamination of the production process due to falling off will increase.
0.001 to 10% by weight is preferable, 0.005 to 5% by weight is more preferable, and 0.01 to 1% by weight is further preferable.

The shape of the particles in the present invention is not particularly limited, but if the particles have a sharp angle, scratches may be generated in the precursor and the strength may be reduced, so particles having no sharp angle are preferable.

If the average particle diameter of the silicone rubber particles in the present invention is too small, the gap between the single yarns becomes small, and conversely, if it is too large, it becomes difficult to enter between the single yarns and the strength improving effect becomes small. Fine particles of ˜50 μm are preferable, 0.07 to 10 μm are more preferable, and 0.1 to 1 μm.
m is more preferred.

As will be described later, it is desirable that the silicone rubber particles in the present invention be continuously applied in the spinning process, and therefore it is preferable to use them after water dispersion. If the particles once dried are fine particles, it is difficult to sufficiently disperse them in water. Therefore, it is preferable to use an aqueous dispersion of silicone rubber particles which are originally granulated by irradiating an electron beam on a silicone dispersion liquid which has been emulsified in water.

In order to define the silicone rubber particles in the present invention, it is necessary to separate the particles from the precursor by the following method.

About 5 g of the precursor according to the present invention is immersed in 200 cc of a good precursor solvent and heated at 120 ° C. for 2 hours to dissolve the precursor. Then, it is filtered with a glass fiber filter, washed with a solvent of 100 cc or more and pure water of 100 cc or more in order, and dried at 120 ° C. for 2 hours to separate the particles, which are then weighed. For example, in the case of a precursor using acrylic carbon fiber, dimethyl sulfoxide is used as a solvent.

The carbon fiber of the present invention may be any of acrylic type, pitch type, rayon type and the like. Next, an example of a method for producing an acrylic type carbon fiber will be described.

The polyacrylonitrile constituting the precursor of the acrylic carbon fiber is preferably a polymer containing 85% by weight or more of acrylonitrile and 15% by weight or less of a polymerizable unsaturated monomer copolymerizable with acrylonitrile. Examples of the polymerizable unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid and their alkali metal salts, ammonium salts and alkyl esters, acrylamide, methacrylamide and their derivatives, allylsulfonic acid, methallylsulfonic acid and Examples thereof include salts or alkyl esters thereof. In addition, it is preferable to copolymerize a polymerizable unsaturated monomer such as an unsaturated carboxylic acid which promotes a flame-resistant reaction. The copolymerization amount is preferably 0.1 to 10% by weight, more preferably 0.3 to 5% by weight, and 0.1 to 10% by weight.
More preferably, it is 5 to 3% by weight. Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid,
Examples thereof include itaconic acid, crotonic acid, citraconic acid, ethacrylic acid, maleic acid, mesaconic acid and the like.
In order to obtain high-strength carbon fibers, it is preferable to copolymerize at least one selected from alkyl esters of unsaturated carboxylic acids and vinyl acetate. The copolymerization ratio is preferably 0.1 to 10% by weight, and 0.3 to 5
It is more preferably in the range of 0.5% by weight and even more preferably in the range of 0.5 to 3% by weight. Specific examples of the alkyl ester of unsaturated carboxylic acid include methyl acrylate, methyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, and secondary butyl methacrylate. Among them, methyl acrylate is preferable. Preferred are propyl, butyl, isobutyl and secondary butyl esters of methacrylic acid.

As the polymerization method, suspension polymerization, solution polymerization,
A conventionally known method such as emulsion polymerization can be employed.
The degree of polymerization has an intrinsic viscosity [η] of preferably 1.0 or more, more preferably 1.25 or more, still more preferably 1.5 or more. The intrinsic viscosity [η] is preferably 5.0 or less from the viewpoint of spinning stability.

As the solvent in the case of solution spinning, known organic and inorganic solvents can be used, and specifically, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, nitric acid, aqueous solution of rhodanese, aqueous solution of zinc chloride and the like are used. The polymer solution to be used is the spinning dope.

The polymer can be made into a precursor by a known method. The spinning may be carried out by a wet spinning method in which it is directly spun into a coagulation bath, a dry-wet spinning method in which it is once spun into air and then coagulated in the bath, or a dry spinning method or melt spinning, but high strength carbon fiber The dry-wet spinning method is preferable for obtaining the above.

In the case of the spinning method using a solvent and a plasticizer, the spun yarn may be directly drawn in the bath, or may be washed in water to remove the solvent and the plasticizer and then drawn in the bath. The condition of stretching in a bath is usually about 2 to 6 times stretching in a stretching bath at 50 to 98 ° C. The dried and densified yarn is dried by a hot drum or the like after drawing in a bath to achieve dry densification. The drying temperature, time and the like can be appropriately selected.
If necessary, the dried and densified yarn is also stretched at a higher temperature (for example, in pressure steam), whereby a precursor having a predetermined fineness and orientation can be obtained. Also, prior to drying and densification,
It is preferable to add a silicone oil agent for the purpose of imparting heat resistance.

The silicone rubber particles may be applied during any of the above-mentioned spinning steps, but it is preferable to apply the silicone rubber particles in a region where the yarn width is wide in order to uniformly apply the silicone rubber particles into the bundle of precursors. It is preferable to add silicone rubber particles dispersed in water in a process oil bath or the like. It is also possible to apply a mixed solution of the process oil and the silicone rubber particles in the process oil bath. It is also possible to add silicone rubber particles before or after applying the step oil agent, and to insert a drying step therebetween. The amount of the silicone rubber fine particles at that time is preferably 0.001 to 100% by weight, more preferably 0.005 to 10% by weight, as a dry weight, based on the weight ratio of the process oil agent and the particles as a whole.
More preferably, 01 to 1% by weight.

The oil agent and the silicone rubber particles may be applied by applying a thread to a driven or non-driving roller in an oil agent bath or a fixed or non-fixed guide bar to apply the thread to the thread, or an oil agent blown upward. Various methods such as a method of running the yarn in the liquid and applying it, a method of dropping the oil solution from above the running yarn, a method of running the thread in the space sprayed with the oil solution, and the like are selected appropriately. be able to.

Further, the silicone rubber particles may be mixed and dispersed in the polymer stock solution to be spun to give the particles to the fiber surface.

In the spinning step, the silicone rubber particles may not be applied and may be applied prior to the subsequent firing step, but from the viewpoint of uniform application, application in the above-mentioned spinning step is preferred. The thread width when the silicone rubber particles are applied is preferably 3 mm or more, more preferably 10 mm or more, still more preferably 20 mm or more per 3000 filaments.

In the practice of the present invention, a dense precursor is effective for obtaining a high-strength carbon fiber. As the denseness, a dense precursor having a lightness difference ΔL measured by an iodine adsorption method of preferably 45 or less, more preferably 30 or less, still more preferably 15 or less is good.
Means for obtaining a dense precursor having a lightness difference ΔL of 45 or less includes dry-wet spinning, increasing the concentration of the spinning dope, lowering the temperature of the spinning dope and coagulation bath solution, and reducing the tension during coagulation. It is effective to keep the degree of swelling low and to keep the degree of swelling of the bath-drawn yarn low by optimizing the number of drawing steps, the draw ratio and the drawing temperature during bath drawing.

In the present invention, the brightness difference ΔL is a value obtained by the following method. About 0.5 g of a dry sample having a fiber length of 5 to 7 cm was precisely weighed and placed in a 200 ml Erlenmeyer flask with a stopper, and an iodine solution (I ₂ : 51 g, 2,4-dichlorophenol 10 g, acetic acid 90 g and iodinated was added thereto. 100 g of potassium is precisely weighed, transferred to a 1-liter measuring flask and dissolved in water to a constant volume) 100 ml is added, and the mixture is heated at 60 ° C. for 5 minutes.
The adsorption treatment is performed while shaking for 0 minutes. After washing the sample with adsorbed iodine in running water for 30 minutes, centrifugal dehydration (2
(000 rpm x 1 minute) and air dry quickly. After opening this sample, Hunter color difference meter [Color Machine Co., Ltd.
Manufactured by CM-25 type], and the brightness (L value) is measured (L ₁ ).

On the other hand, the corresponding sample not subjected to the adsorption treatment of iodine was opened, and the lightness (L ₀ ) was measured by the Hunter color difference meter in the same manner, and the lightness difference ΔL was obtained from L ₀ -L ₁ . .

From the viewpoint of improving the strength, the single fiber fineness of the precursor is preferably small so as not to cause firing unevenness in the subsequent flameproofing step, preferably 1.5 d or less, more preferably 1.0 d or less, and further preferably. Is 0.8d or less.

By firing such a precursor, a high performance carbon fiber can be obtained. As the flameproofing condition, a conventionally known method can be adopted, a tension or stretching condition is preferably used in the range of 200 to 300 ° C. in an oxidizing atmosphere, and a density is preferably 1.25 g.
/ Cm ³ or more, more preferably 1.30 g / cm ³ or more until heat treatment is reached. This density is 1.60 g /
It is generally not more than cm ³ , and if the density is too large, the physical properties may deteriorate, which is not preferable. Generally, for the atmosphere, known air, oxygen, nitrogen dioxide,
Although an oxidizing atmosphere such as hydrogen chloride can be used, air is preferable from the economical point of view.

The flame-proofed yarn is carbonized in an inert atmosphere by a conventionally known method. The carbonization temperature is preferably 1000 ° C. or higher in view of the physical properties of the resulting carbon fiber, and if necessary, graphitization can be performed at a temperature of 2000 ° C. or higher. Moreover, 350-500 degreeC and 1000-
The temperature rising rate at 1200 ° C. is preferably 500 ° C. /
Min or less, more preferably 300 ° C./min or less, still more preferably 150 ° C./min or less. Thereby, a dense carbon fiber having few internal defects such as voids can be obtained. If the heating rate is 10 ° C./minute or less, the productivity will be too low. Also, 350 to 500 ° C or 230
At 0 ° C. or more, it is important to perform stretching at 1% or more, more preferably 5% or more, further preferably 10% or more, in order to improve the denseness. Stretching of more than 40% is not preferable because fluffing tends to occur.

The carbon fiber thus obtained is subjected to electrolytic oxidation treatment in an electrolytic cell made of an acid or alkali aqueous solution or oxidation treatment in a gas phase or a liquid phase to give a carbon fiber in a composite material. It is preferable to improve the affinity and adhesiveness between the matrix resin and the matrix resin. In the present invention, in particular, electrolytic oxidation is preferable because it can be oxidized in a short time and the degree of oxidation can be easily controlled.

As the electrolytic solution for electrolytic treatment, either acidic or alkaline electrolytic solution can be adopted. As an acidic electrolyte,
Specific examples include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid and carbonic acid, organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid and maleic acid, and salts such as ammonium sulfate and ammonium hydrogensulfate. Sulfuric acid and nitric acid which show strong acidity are preferable.

Specific examples of the alkaline electrolyte include hydroxides such as sodium hydroxide, potassium hydroxide and barium hydroxide, inorganic salts such as ammonia, sodium carbonate and sodium hydrogen carbonate, sodium acetate and benzoic acid. Organic salts such as sodium, these potassium salts,
Examples thereof include barium salts or other metal salts, and ammonium salts, and organic compounds such as tetraethylammonium hydroxide or hydrazine. Among them, ammonium carbonate, ammonium hydrogencarbonate, tetrahydroxide, etc., which do not contain an alkali metal which causes a curing failure of the resin are preferable. Alkyl ammoniums and the like are preferable.

The amount of electricity is preferably optimized according to the carbonization degree of the carbon fiber to be treated. From the viewpoint of controlling the deterioration of the crystallinity of the surface layer within an appropriate range, the total amount of electricity in the energization treatment is 5 to
It is preferably in the range of 1000 coulomb / g, more preferably 10 to 500 coulomb / g.

After the electrolytic treatment or the washing treatment, it is preferable to wash with water and dry. In this case, if the drying temperature is too high, the functional groups present on the re-surface of the carbon fiber are likely to be lost by thermal decomposition. Therefore, it is desirable to dry at the lowest possible temperature. Specifically, the drying temperature is 250 ° C.
Hereafter, it is preferable to dry at 210 ° C. or lower.

If necessary, sizing can be performed by a conventionally known technique.

In the present invention, the mechanical properties of the carbon fiber produced from the carbon fiber producing precursor are as follows.
Tensile strength of resin-impregnated strand is usually 300kg
f / mm ² or more, preferably 400 kgf / mm ²
Or more, more preferably 500 kgf / mm ² or more, more preferably 600 kgf / mm ² or more. The tensile modulus of the carbon fiber is 20 × 10 ³ kgf / mm ²
The above is desirable, preferably 22 × 10 ³ kgf / mm ² or more, more preferably 24 × 10 ³ kgf / mm ² or more, and further preferably 28 × 10 ³ kgf / mm ² or more. Each of the above strand strength or elastic modulus is 300 kgf
/ Mm ² or less, or less than 20 × 10 ³ kgf / mm ² carbon fiber, when made into a composite,
There are cases where desired properties as a structural material cannot be obtained.

[0063]

EXAMPLES The present invention will be described in more detail below with reference to examples. The tensile strength and elastic modulus of the carbon fiber in this example were obtained by the resin-impregnated strand method.
That is, “Bakelite” ERL-4221 (registered trademark, manufactured by Union Carbide Co., Ltd.) / Boron trifluoride monoethylamine (BF ₃ · MEA) / acetone = 10
Carbon fiber was impregnated with 0/3/4 part, and the obtained resin-impregnated strand was heated at 130 ° C. for 30 minutes to be cured,
It was measured according to the resin-impregnated strand test method specified in S-R-7601.

Example 1 As a silicone dispersion, a dimethylsiloxane-based liquid having a basic skeleton represented by the following chemical structural formula (1) was used, and the kinematic viscosity was 2500 × 10 ⁻⁶ m ² / s and the modification amount was 1 weight. %, An amino-modified silicone was dispersed in water, and a dispersion having a silicone concentration of 20% by weight was used.

[0065]

Embedded image The dispersion was put in a vinyl bag, purged with nitrogen, and then heat-sealed. The thickness of the dispersion liquid is set to 1.5 mm, and the acceleration voltage is 750 kV and the dose is 50 kGy.
When the electron beam was irradiated once at a total dose of 300 kGy, a dispersion liquid of silicone rubber fine particles having an average particle diameter of 0.45 μm and a ratio of the maximum diameter to the minimum diameter of 1.05 could be obtained.

Comparative Example 1 An amino-modified silicone dispersion was treated in the same manner as in Example 1 except that it was heated at 80 ° C. for 2 hours instead of being not irradiated with an electron beam, but silicone rubber fine particles could not be obtained. There wasn't.

Example 2 As a silicone dispersion liquid, a dimethylsiloxane-based liquid having a basic skeleton represented by the chemical structural formula (1), a kinematic viscosity of 2500 × 10 ⁻⁶ m ² / s, and a modification amount of 1% by weight. The kinematic viscosity of the amino-modified silicone which is ## STR3 ## and the dimethylsiloxane-based silicone containing the basic skeleton represented by the following chemical structural formula (2) is 1
A dispersion having a silicone concentration of 20 wt% was used in which the same weight of 0000 × 10 ⁻⁶ m ² / s and an epoxy-modified silicone having a modification amount of 1 wt% were dispersed in water.

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Embedded image The dispersion was put in a vinyl bag, purged with nitrogen, and then heat-sealed. The accelerating voltage was 750 kV and the dose was 50 kGy six times so that the thickness of the dispersion liquid was 1.5 mm.
When the electron beam was irradiated at a total dose of 300 kGy, a dispersion liquid of silicone rubber fine particles having an average particle diameter of 0.30 μm and a ratio of the maximum diameter to the minimum diameter of 1.05 could be obtained.

Comparative Example 2 As a silicone dispersion, a dimethylsiloxane-based liquid having a basic skeleton represented by the following chemical structural formula (3) was used, and the kinematic viscosity was 20000 × 10 ⁻⁶ m ² / s and the modification amount was 0. A dispersion having a silicone concentration of 20% by weight was used in which 5% by weight of vinyl-modified silicone and 5% by weight of 2,4-dichlorobenzoyl peroxide were added to the silicone and then dispersed in water.

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Embedded image The dispersion was put in a vinyl bag, purged with nitrogen, and then heat-sealed. This was heated at 80 ° C. for 1 hour, but only a dispersion liquid of silicone rubber fine particles having an average particle diameter of 2.5 μm could be obtained.

Example 3 A dimethylsiloxane-based skeleton containing the basic skeleton represented by the chemical structural formula (2) had a kinematic viscosity of 10,000 × 10 ⁻⁶ m ² /
s, an epoxy-modified silicone having a modification amount of 1% by weight was dispersed in water, and a dispersion having a silicone concentration of 20% by weight was used. The dispersion was put in a vinyl bag, purged with nitrogen, and then heat-sealed. Thickness of dispersion is 1.5mm
When the electron beam was irradiated 10 times with an acceleration voltage of 750 kV and a dose of 50 kGy at a total dose of 500 kGy, the average particle diameter was 0.25 μm, and the ratio of the maximum diameter to the minimum diameter was 1.05. A dispersion liquid of silicone rubber fine particles could be obtained.

Example 4 By a solution polymerization method using dimethyl sulfoxide as a solvent,
A spinning dope having an intrinsic viscosity [η] of 1.70 and a polymer concentration of 20%, which was composed of 99% by weight of acrylonitrile and 1% by weight of itaconic acid, was obtained. This was once discharged into the air through a 3000 filament spinner and allowed to run in a space of about 3 mm, then coagulated in a 30% aqueous solution of dimethyl sulfoxide at 10 ° C, and the coagulated yarn was washed with water and then bathed up to 4 times. After stretching, a process oil agent comprising 2% of amino-modified silicone oil agent and 0.1% of silicone rubber fine particles prepared in Example 1 was applied, and then dried and densified. Furthermore, it is drawn up to 2.5 times in pressurized steam and the single yarn fineness is 0.8d and the total fineness is 240.
I got a 0D precursor. The adhesion amount of the silicone rubber fine particles was 0.1%.

The obtained precursor is 240 to 280 ° C.
In the air at a draw ratio of 1.05 and a density of 1.37 g
/ Cm ³ was obtained. Then, in a nitrogen atmosphere, 35
The temperature rising rate in the temperature range of 0 to 500 ° C. was set to 200 ° C./minute, 2% stretching was performed, and then firing was performed up to 1400 ° C.

Subsequently, an aqueous solution of sulfuric acid having a concentration of 0.1 mol / l was used as an electrolytic solution, electrolysis was performed at 10 coulomb / g, and then washed with water,
It was then dried in heated air at 150 ° C. The physical properties of the carbon fiber thus obtained are shown in Table 1.

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[Table 1] Comparative Example 3 A carbon fiber was obtained in the same manner as in Example 3 except that the process oil was 2% of amino-modified silicone oil. The strength of the obtained carbon fiber is shown in Table 2 below.

Example 5 A spinning stock solution having a copolymer composition of 98% by weight of acrylonitrile, 1% by weight of itaconic acid and 1% by weight of isobutyl methacrylate, an intrinsic viscosity [η] of 1.50 and a polymer concentration of 25% was used. A carbon fiber was obtained in the same manner as in Example 3 except for the above. The strength is shown in Table 2.

Comparative Example 4 A carbon fiber was obtained in the same manner as in Example 4 except that the process oil was 2% of amino-modified silicone oil. The strength of the obtained carbon fiber is shown in Table 2.

Example 6 By a solution polymerization method using dimethyl sulfoxide as a solvent,
A spinning dope having an intrinsic viscosity [η] of 1.70 and a polymer concentration of 20%, which was composed of 99% by weight of acrylonitrile and 1% by weight of itaconic acid, was obtained. This was once discharged into the air through a 3000 filament spinner and allowed to run in a space of about 3 mm, then coagulated in a 30% aqueous solution of dimethyl sulfoxide at 10 ° C, and the coagulated yarn was washed with water and then bathed up to 4 times. The film was stretched and a process oil solution containing 2% of an amino-modified silicone oil agent was applied. Further, 30% of the dry weight of the yarn was provided with an aqueous dispersion containing 0.1% of the silicone rubber fine particles prepared in Example 2, and the silicone rubber was squeezed with 10 free rollers having a diameter of 20 mm arranged in a zigzag manner. The fine particles were migrated into the yarn and then dried and densified. Further, it was drawn up to 2.5 times in pressurized steam to obtain a precursor having a single yarn fineness of 0.8 d and a total fineness of 2400D. The adhered amount of particles was 0.02%.

The obtained precursor is 240 to 280 ° C.
In the air at a draw ratio of 1.05 and a density of 1.37 g
/ Cm ³ was obtained. Then, in a nitrogen atmosphere, 35
The temperature rising rate in the temperature range of 0 to 500 ° C. was set to 200 ° C./minute, 2% stretching was performed, and then firing was performed up to 1400 ° C.

Subsequently, using a sulfuric acid aqueous solution having a concentration of 0.1 mol / l as an electrolytic solution, electrolytic treatment was performed at 10 coulomb / g, and then washing with water was performed.
It dried in 150 degreeC heating air. The physical properties of the carbon fiber thus obtained are shown in Table 1 above.

Comparative Example 5 The object of the present invention is to facilitate the provision of silicone rubber particles having a small average particle diameter and the dispersion thereof, which has been difficult to achieve in the above-mentioned prior art, and further, carbon fibers to which the silicone rubber particles are applied. To provide a precursor and a high-strength carbon fiber for use. After applying a process oil agent consisting of 2% of amino-modified silicone oil agent, 30% of water is applied to the dry weight of the yarn, and the diameter is 20 arranged in a zigzag.
A carbon fiber was obtained in the same manner as in Example 5, except that the product was squeezed with 10 mm free rollers and then densified.
The strength of the obtained carbon fiber is shown in Table 2.

Comparative Example 6 The kinematic viscosity of the dimethylsiloxane-based skeleton containing the basic skeleton represented by the chemical structural formula (3) is 20000 × 10 ⁻⁶ m ² /
s, a vinyl-modified silicone having a modification amount of 0.5% by weight, and 5% by weight of 2,4-dichlorobenzoyl peroxide are added to the silicone, and then heated at 80 ° C. for 1 hour to obtain a silicone rubber, This was pulverized to prepare silicone rubber fine particles having an average particle diameter of 50 μm. After applying the process oil agent consisting of 2% of amino-modified silicone oil agent,
Other than that the aqueous suspension containing 0.1% of the silicone rubber fine particles was applied at 30% to the dry weight of the yarn, and was squeezed by 10 free rollers having a diameter of 20 mm arranged in a zigzag and then dried and densified. A carbon fiber was obtained in the same manner as in Example 5. Similarly, the strength is shown in Table 2.

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[Table 2]

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EFFECTS OF THE INVENTION According to the present invention, it is possible to facilitate the provision of silicone rubber particles having a small average particle diameter and a dispersion containing the same, which has been difficult in the prior art, and to efficiently provide these. Further, it is possible to obtain a precursor for carbon fiber for obtaining high-strength carbon fiber by applying such silicone rubber particles and a high-strength carbon fiber.

Claims (15)

[Claims] 1. A silicone rubber obtained by curing silicone by irradiating it with an electron beam. 2. Silicone rubber particles obtained by irradiating silicone with an electron beam to granulate the silicone. 3. The silicone according to claim 2, wherein the silicone comprises an amino-modified silicone and / or an epoxy-modified silicone.
The described silicone rubber particles. 4. The silicone rubber particle according to claim 2 or 3, wherein the silicone rubber particle has a substantially spherical shape. 5. The average particle size of the silicone rubber particles is 1 μm or less, and the average particle size is preferably 2 μm or less.
Silicone rubber particles according to any of the above. 6. A silicone rubber dispersion obtained by dispersing the silicone rubber particles according to any one of claims 2 to 5 in a liquid. 7. The silicone rubber dispersion according to claim 6, wherein the silicone concentration in the silicone dispersion is 5% by weight or more. 8. A method for producing silicone rubber particles, which comprises granulating a silicone or silicone dispersion by irradiating it with an electron beam. 9. The method for producing silicone rubber particles according to claim 8, wherein the irradiation dose of the electron beam is 50 kGy or more. 10. The electron beam is irradiated a plurality of times.
Alternatively, the method for producing silicone rubber particles according to claim 9. 11. The method for producing silicone rubber particles according to claim 8, wherein an irradiation dose of the electron beam per irradiation is 10 to 500 kGy. 12. The method for producing silicone rubber particles according to claim 8, wherein the electron beam is irradiated from a plurality of directions. 13. The method for producing silicone rubber particles according to claim 8, wherein the minimum value of the absorbed dose with respect to the maximum value of the absorbed dose of the electron beam is 0.4 or more. 14. A precursor for carbon fibers, which has the silicone rubber particles according to any one of claims 2 to 13 on the fiber surface. 15. A carbon fiber obtained by firing the precursor for carbon fiber according to claim 14.