JPH0424259A - Granular carbon fiber aggregate - Google Patents

Abstract

PURPOSE:To obtain the title aggregate useful as a composite material, etc., having a granular aggregate shape, particle diameters in a given range, a particle diameter distribution of plural peaks, excellent blending properties and fluidity in a specific carbon fiber aggregate. CONSTITUTION:In a carbon fiber aggregate having 0.01-4mum, preferably 0.05-1mum diameter of fibers and 5-10,000, preferably 20-500 ratio of fiber length/fiber diameter, the shape of the aggregate is granular, the particle diameters distribute in a range of 0.1-5mm and the particle diameter distribution has plural peaks between 0.1-0.4mm and 1-2mm to give the objective aggregate.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a granular carbon fiber aggregate, and more specifically, to handling of a carbon fiber aggregate obtained by a vapor phase method and to resin/rubber processing. The present invention relates to a granular carbon fiber aggregate that has improved crosstalk properties.

[Conventional technology]

Carbon fiber has excellent properties such as high strength and high modulus of elasticity.
It is a material that has been in the spotlight in recent years as a variety of composite materials.

Conventionally, carbon fibers have been mainly produced by carbonizing organic fibers, but vapor-grown carbon fibers produced by thermal decomposition and catalytic reactions of hydrocarbons are also known. Vapor-grown carbon fibers have superior crystallinity and orientation compared to the former carbon fibers, and are therefore expected to be used in a wide variety of fields as a material that has both high strength and high modulus of elasticity. Examples of such vapor-grown carbon fiber include Japanese Patent Application Laid-Open No. 61-132
No. 630, No. 61-132600, No. 61-
No. 132663, No. 61-225325, No. 61-225319, No. 61-225320, No. 60-215816, No. 61-70014
The ones shown in the No. 1 gazette, etc. are known.

However, according to studies by the present inventors, the vapor-grown carbon fibers related to these patent applications have a bulk density of 0.04 g/c.
Because it is small as nr and has a large volume relative to its weight,
There are problems with ease of handling during storage and transportation. In particular, when used as a reinforcing filler for resins, combs, etc., if it is fed as is to an extruder or to a roll kneader, there is a problem that it is difficult to penetrate and can only be uniformly dispersed into resins, combs, etc. Ta.

Further, JP-A-1-270543 discloses a vapor-grown carbon fiber granule, but its bulk density is 0.05
~0.2 g/cnf, and when kneading with resin, if the vapor-grown carbon fiber granules and resin are blended in advance and then put into the hopper, segregation will occur in the hopper due to the difference in bulk density between the two, resulting in a constant There was a problem in that it was difficult to knead the composition.

[Problem to be solved by the invention]

The purpose of the present invention is to provide convenient storage and transportation, good handling properties, and in particular, to improve biting into the extruder etc. when kneading with resin, rubber, etc., to suppress segregation in the hopper, and to suppress segregation in the hopper. The object of the present invention is to provide a granular carbon fiber aggregate that can be uniformly and easily dispersed in rubber or the like.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the present inventors have made extensive studies and found that certain vapor-grown carbon fibers are made into granular aggregates having a certain particle size distribution. The inventors have found that the above-mentioned problems can be significantly improved, and have arrived at the present invention.

That is, the present invention is as follows.

(1) The fiber diameter is 0.01 to 4 μm, and the fiber length/fiber diameter (hereinafter referred to as aspect ratio) is 5 to 1oooo
In the aggregate of carbon fibers, the aggregate shape is granular, and the particle size is distributed in the range of 0.1 to 5 mm,
A granular carbon fiber aggregate characterized in that the particle size distribution has a plurality of peaks.

(2) The particle size distribution of the granular carbon fiber aggregate is 0.1 to 0.
．． The granular carbon fiber aggregate according to claim 1, having a plurality of peaks between 4 mm and 1 to 2 mm.

The diameter of the carbon fiber of the present invention is 0.01 to 4 μm, preferably 0.01 to 2 μm, particularly preferably 0.0
It is 5 to 1 μm.

Further, the length/diameter ratio of carbon fibers, that is, the aspect ratio, is 5 to 10,000, preferably 10 to 1,000,
Particularly preferably 20 to 500. Aspect ratio
If it is smaller than O, the reinforcing effect of resin, rubber, etc. will be reduced, and if it exceeds 10,000, the molding processability will deteriorate, such as an increase in melt viscosity.

In order to produce the carbon fiber of the present invention, for example,
As shown in JP231821, JP61-225322, JP61282427, etc., it is produced by subjecting hydrocarbons to a thermal decomposition catalytic reaction in the space of a heating zone.

The shape of the aggregate of carbon fibers in the present invention is granular, and a shape close to a spherical shape is preferred because of its good fluidity. It is preferable that the particle size of the aggregate is distributed in a range of 0.1 to 5 mm. If the particle size is less than 0.1 mm, the fluidity will decrease and the bite into an extruder, roll kneader, etc. will be poor.
If it exceeds mm, the dispersibility will deteriorate. Furthermore, it is necessary that the particle size distribution of the above-mentioned aggregate has a plurality of peaks.

Having multiple peaks in the particle size distribution improves the filling rate of the carbon fibers, increases the bulk density of the carbon fiber aggregate, and prevents segregation because the difference in bulk density with the resin decreases. It is effective to do so.

When a plurality of peaks exist between 0~0.4 mm and 1~2 mm, it is possible to obtain the carbon fiber aggregate which not only has an increased bulk density but also has better fluidity, dispersibility in resin, etc. can. Furthermore, it is more preferable to exist between 0.2-0.4 mm and 1-1.5 mm. Here, the term plurality refers to two or more. The shape of the particle size distribution is 0.1 to 5+
Continuously distributed in the range of ++m and 0.1 to 0.4m
There may be a peak or multiple peaks between m and 1 to 2 mm,
Alternatively, peaks may exist outside the above range, or shapes may exist only in the ranges of 0.1 to 0.4 mm and 1 to 2 mm, and are not particularly limited. Although the number of peaks and the ratio of their sizes are not particularly limited, they should be set to have an optimum particle size distribution in consideration of fluidity, bulk density, dispersibility in resin rubber, etc. Particle size and particle size distribution can be measured using known particle size distribution measurement techniques. For example, a granular carbon fiber aggregate is observed under an optical microscope, and the particle size and particle size distribution are analyzed using an image processing device. A method of doing so is preferred.

The granular carbon fiber aggregate in the present invention has a bulk density of 0.1
~0.5 g/cnf, preferably 0.2-0.5 g
/cm3. When the bulk density is less than 0.1 g/cm, when the aggregate and the resin are blended and then put into a hopper, segregation in the hopper becomes significant and the composition of the carbon fibers in the resin changes. It changes over time, and if it exceeds 0.5 g/cnr, the dispersibility deteriorates. The bulk density is calculated by mass/volume by filling a 500 cm graduated cylinder with 450 cnr or more of granular carbon fiber aggregates, measuring the volume and mass at that time.

The granular carbon fiber aggregate according to the present invention is characterized by extremely excellent fluidity, and the angle of repose, which is a measure of fluidity, is 25 to 50 degrees, preferably 25 to 40 degrees.

The angle of repose here is determined by supplying the aggregate from above onto a horizontal surface to form a circular pile, and measuring the inclination angle of the slope.

The most important point of the present invention is to adjust the particle size distribution of the granular carbon fiber aggregate in order to optimize the physical properties of the granular carbon fiber aggregate, such as bulk density, fluidity, and dispersibility in the resin.

In the present invention, carbon fibers include those that have been pulverized to the fiber diameter and aspect ratio specified in the present invention, those that have been further oxidized and introduced with oxygen-containing functional groups, and those that have been subjected to an oxidation treatment to introduce oxygen-containing functional groups, It may also be one that has been heat-treated in an atmosphere.

The method for producing the granular carbon fiber aggregate in the present invention is not particularly limited, but for example, the carbon fibers obtained by the above production method may be placed in a mixer configured by disposing a plow-like shovel in a horizontal drum. Alternatively, the carbon fibers are crushed, oxidized, and heat treated, and the shovel is rotated to cause the carbon fibers to flow three-dimensionally, and a granulation aid is added to the carbon fibers in this state. The fibers are formed into granular aggregates.

The particle size distribution, bulk density, etc. of the granular carbon fiber aggregates change depending on the rotation speed of the shovel, the type and amount of granulation aid, the method of injection, and the granulation time, so that the desired aggregate can be obtained. Therefore, it is necessary to adjust the above granulation conditions. For example, if the amount of granulation aid added is increased, the aggregate with a large particle size and a high bulk density can be obtained, and if the number of rotations of the shovel is increased, the particle size becomes smaller. Furthermore, as a matter of course, changing the diameter and aspect ratio of the carbon fibers used will change the particle size distribution of the aggregate under the same granulation conditions, so it is necessary to adjust the granulation conditions depending on the form of the carbon fibers used.

The granular carbon fiber aggregates of the present invention can be obtained by classifying the granular carbon fiber aggregates formed by the apparatus and method described above using a sieve or the like, and blending the classified aggregates. It is also preferable to continuously produce a granular carbon fiber aggregate, in which the carbon fibers and granulation aid are continuously introduced into the mixer, and the continuously treated mixture is discharged, classified and blended. The method and apparatus for producing granular carbon fiber aggregates according to the present invention are not limited to the above examples, but include a method using an apparatus that does not cause the carbon fibers to flow three-dimensionally and can simultaneously add a granulation aid; Methods that do not use granulation aids are also used.

The granulation aid is not particularly limited to any liquid that imparts cohesive properties to the carbon fibers, but examples thereof include water, alcohols such as methanol, ethanol, and propatool, ketones such as acetone and methyl ethyl ketone, Organic solvents such as hydrocarbons such as hexane, cyclohexane, benzene, toluene, etc., organic compounds dissolved in water, organic solvents, mechanically dispersed, and dispersed with surfactants are used. It will be done. Organic compounds here include natural compounds such as starch, cyclodextrin, amino acids, peptides, proteins, natural rubber, soybean oil, coconut oil, etc.
S resin, vinylidene chloride latex, vinyl chloride resin, butadiene resin, fluorine resin, polyacetal, polyamide such as nylon 6 and nylon 66, polyarylate, polyetherimide, polyether ether ketone,
Polyesters such as polyethylene, polyethylene oxide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polystyrene, polysulfone, polyvinyl ether, polyphenylene oxide,
Thermoplastic resins such as polyphenylene sulfide, polypropylene, methacrylic resins, precursors and monomers of the resins, modified products of the resins, epoxy resins, xylene resins, vinyl ester resins, phenolic resins, unsaturated polyester resins, furan resins, Thermosetting resins such as polyimide, polyurethane, melamine resin, urea resin, precursors and monomers of the resin, modified products of the resin, styrene/butadiene latex, butadiene latex, neoprene/butadiene latex, chloroprene rubber , urethane rubber, silicone rubber, fluorine rubber, synthetic rubber such as acrylic rubber, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, tris-(2-methoxyethoxy)vinylsilane, γ-glycidoxypropyltrimethoxysilane , 3-(trimethoxysilyl)propyl methacrylate, γ(2-amineethyl)aminopropyltrimethoxysilane, γchloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. Ringing agent, isopropyl triisostearoyl titanate, isopropyl tridecyl benzene sulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, tetraisopropyl bis(
Dioctyl phosphite) titanate, Tetraoctyl bis(ditridecyl phosphite) titanate, Bis(dioctyl pyrophosphate) oxyacetate titanate, Isopropyltrioctanoyl titanate, Isopropyl dimethacrylic isostearoyl titanate, Isoprobyl isostearoyl diacryl titanate, Isopropyl These include titanium-based coupling agents such as tri(dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, and isopropyl tri(N-aminoethyl-aminoethyl) titanate. Examples of surfactants include anionic surfactants such as alkyl ether carbonate, cationic surfactants such as aliphatic quaternary ammonium salts and imidazolinium salts, and amphoteric surfactants such as carboquinhetain type. Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene glycerin fatty acid ester, and polyethylene glycol fatty acid ester can be used.

From the viewpoint of safety, the granulation aid is preferably water, an organic compound dissolved in water, mechanically dispersed, or dispersed with a surfactant. When using carbon fiber aggregates for various purposes,
It is desirable that no organic compounds that may become impurities remain, and it is preferable to use water as a granulation aid. However, in order to improve the strength of the aggregate, it is also preferable to dissolve an organic compound in water or to disperse it with a surfactant. It is necessary to select the most suitable granulation aid depending on the intended use.

The amount of the granulation aid needs to be adjusted depending on the equipment used for production, production conditions, the type of granulation aid used, etc. so as to obtain the most preferable granular carbon fiber aggregate.

Drying is required to remove water and organic solvent contained in the granulation aid. The drying method is not particularly limited, and known techniques can be used. In the case of using only water or an organic solvent, the drying temperature is preferably 4008 C or less, and the drying is preferably carried out in an inert atmosphere such as nitrogen or argon.

When an organic compound is used, drying is performed at a temperature at which the organic compound does not change in quality.

〔Example〕

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

Examples 1 to 3, Comparative Examples 1 to 2 Iron trisacetylacetonate and benzene were introduced into a heating space at 1400°C and produced in a floating state. 1 kg of carbon fiber with a fiber diameter of 0.02 to 0.3 μm and an aspect ratio of 50 to 400 was put into a Lodige mixer (manufactured by Kenpan Giken Co., Ltd.) with an internal volume of about 100 n, and the shovel rotation speed was 8 orpm.
The carbon fibers were made to flow three-dimensionally at a chopper rotation speed of 300 rpm. Continuously add 4 kg of water as a granulation aid and granulate for 5 minutes.
It was dried at °C and classified and blended to obtain a granular carbon fiber aggregate.

The obtained aggregates were evaluated as Example 1.2.3 and Comparative Example 1.2 based on the particle size distribution. FIG. 1 shows the particle size distribution of Examples 1 to 3, and FIG. 2 shows the particle size distribution of Comparative Examples 1.2. The average particle size, bulk density, angle of repose, and composite with resin of the aggregate were evaluated for biting extrudability and dispersibility.

The composite with resin was performed using polypropylene as the matrix resin. The bite and extrusion properties of the extruder are 3.
0+r+m twin screw extruder (manufactured by Ikegai Iron Works, PCM-30)
It was evaluated. In addition, segregation within the hopper was also evaluated.

Further, the dispersibility of carbon fibers was evaluated by observing the surface condition and cross section of the extruded strand using a scanning electron microscope.

The results are shown in Table 1.

Table * a) Very little ◎, some ○, quite a bit
A granular carbon fiber aggregate was obtained in the same manner as in Example 1 except that a carbon fiber (manufactured by Kisso Yuka Co., Ltd., solid content: 1.25%) was used. The average particle diameter, bulk density, angle of repose, and extrudability, dispersibility, and segregation of the aggregate were evaluated in combination with resin. The results are shown in Table 2.

Further, the particle size distribution is shown in FIG.

Table 2 [Effects of the Invention] The granular carbon fiber aggregate according to the present invention has a large bulk density and good fluidity, so it is convenient to store and transport, has good handling, and is especially suitable for kneading with resins, rubber, etc. When doing so, it is extremely useful because it improves the biting into the extruder, etc., suppresses segregation in the hopper, and allows it to be uniformly and easily dispersed in resins, rubbers, etc.

[Brief explanation of drawings]

FIG. 1 shows the particle size distribution of the granular carbon fiber aggregates of Examples 1 to 3, FIG. 2 shows the comparative examples I and 2, and FIG. 3 shows the granular carbon fiber aggregates of Example 4.5.

Claims (2)

[Claims] (1) In an aggregate of carbon fibers with a fiber diameter of 0.01 to 4 μm and a fiber length/fiber diameter of 5 to 10,000, the aggregate shape is granular, and the particle size is 0.1 to 5 mm.
1. A granular carbon fiber aggregate characterized in that the particle size distribution is distributed in a range of 1 to 1, and the particle size distribution has a plurality of peaks. (2) The particle size distribution of the granular carbon fiber aggregate is 0.1 to 0.
．． The granular carbon fiber aggregate according to claim 1, having a plurality of peaks between 4 mm and 1 to 2 mm.