JPH03250503A - Conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain a high conductive composition by dispersingly mixing graphite fiber and conductive carbon black in a prescribed amount respectively with synthetic resin. CONSTITUTION:The conductive resin composition is made up by dispersingly mixing 10-100 weight part of graphite fiber and 10-80 weight part of conductive carbon black with 100 weight part of synthetic resin. For graphite fiber used for this conductive resin composition, one which is graphitized by heat-treating carbon fiber, obtained by pyrolyzing such organic fiber as acryl fiber at a high temperature or by vapor-phase-cracking hydrocarbon, in an inert gas atmosphere is used. For a conductive carbon black, one which has been conventionally used for providing conductivity to synthetic resin can be used. As synthetic resin which can be used for this conductive resin composition, polyethylene, polypropylene, etc., is used. It is thereby possible for the conductive resin composition to be a light composite material in which a carbonaceous conductive material is used in place of expensive metal fiber and also to be used for current shielding, etc., because of the high conductivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrically conductive composite material composition suitable for producing electrically conductive molded articles or for use as a paint, an adhesive, or the like.

``Prior art'' With the development of electronics technology, there has been a demand for conductive resin compositions that are lightweight, have high strength, high conductivity, and have excellent moldability for use as shielding materials for static electricity and electromagnetic waves. Furthermore, there is a demand for conductive paints to impart conductivity to synthetic resin molded products, conductive adhesives to form conductive bonds, etc. Such conductive compositions are generally composites made by blending particles or fibers of conductive substances such as metals and carbon with synthetic resins such as rubber and plastics.

In such conventional composite resin compositions, those using metal materials as conductive substances are generally heavy and have the disadvantage that conductive performance easily deteriorates due to oxidation, and if materials that are resistant to deterioration are selected, they may be extremely expensive. be. On the other hand, carbon materials as conductive substances generally have lower conductivity than metal materials, so if a powder material such as carbon black is to be used to obtain a composite resin composition with low resistance, a large amount must be added. Therefore, the viscosity of the resin composition increases significantly, and the processability significantly decreases. Furthermore, when kneading the resin or molding the resin into a desired shape, the carbon black stractures break due to shearing and the electrical resistivity changes, making it difficult to obtain the desired electrical resistivity. There is a problem that the resistivity changes.

In addition, there have been proposals to incorporate carbon fiber, whose electrical resistivity is less likely to change, in place of carbon black. ! -65144 discloses a resin composition in which graphitized vapor-grown carbonaceous fibers are dispersed in a synthetic resin, but this composite resin composition has a volume resistivity of 10-1 to 10'Ω. However, the volume resistivity of 10 −2 Ω, which is required for electromagnetic shielding materials at the national level, could not be achieved.

Problems to be Solved by the Invention] Under these circumstances, the present invention provides a conductive composite resin material that maintains high and stable conductivity and can be used as an electromagnetic shielding material. This is what I am trying to do.

[Means to solve the problem]

The above object of the present invention is achieved by a conductive resin composition prepared by dispersing and blending 10 to 100 parts by weight of graphite fibers and 10 to 80 parts by weight of conductive carbon black to 100 parts by weight of a synthetic resin. I can do it.

As the graphite fibers used in the conductive resin composition of the present invention, carbon fibers obtained by thermally decomposing organic fibers such as acrylic fibers at high temperatures or by vapor phase thermally decomposing hydrocarbons can be used, for example. It is possible to use graphitized carbon fibers that have been heat-treated in an inert gas atmosphere, but graphitized vapor-grown carbon fibers are particularly preferred.

Such vapor-grown carbon fibers are produced using hydrocarbon compounds such as aromatic hydrocarbons such as toluene, benzene, and naphthalene, and aliphatic hydrocarbons such as propane, ethane, and ethylene, preferably benzene or naphthalene, as raw materials. It can be obtained by gasifying the raw material and contacting and decomposing it with a hydrocarbon decomposition catalyst at a high temperature of, for example, 900°C or higher, together with a carrier gas such as hydrogen.
Catalysts consisting of ultrafine metal particles dispersed and suspended in a reaction zone at 0°C, such as those obtained by contacting and decomposing iron, nickel, iron-nisogal alloy, etc. with a particle size of 100 to 300 angstroms, are preferably used. It will be done.

The carbon fibers thus obtained are pulverized using a ball mill, rotor speed mill, cutting mill, or other suitable pulverizer, if necessary. Although grinding is not necessary,
It is preferable to carry out this method because it improves the dispersibility when blending with the synthetic resin and improves the performance of the composite resin composition.

Furthermore, the carbon fiber thus obtained is heated at 1500 to 3500°C.
, preferably at a temperature of 2500-3000'C, 3-1
Graphite fibers with preferable properties can be obtained by heat treatment for 20 minutes, preferably 30 to 60 minutes, in an atmosphere of an inert gas such as argon.

Further, as the conductive carbon black to be blended into the conductive resin composition of the present invention, carbon black that has been conventionally used to impart conductivity to synthetic resins can be used, such as Ketchen manufactured by Lion Akzo. Black EC (trade name) or the like can be used.

Examples of the synthetic resin used in the conductive resin composition of the present invention include thermoplastic resins such as polyethylene, polypropylene, polyvinyl chloride, ethylene/vinyl acetate copolymer, ethylene/acrylic acid ester copolymer, and silicone resin. , thermosetting resins such as phenolic resins, urea resins, epoxy resins, and also e.g. chloroprene, chlorosulfonated polyethylene, chlorinated polyethylene, ethylene-α
- Rubbers such as olefin rubber, ethylene-propylene rubber, silicone rubber, acrylic rubber, and fluororubber can be used.

As a method for blending and dispersing graphite fibers and conductive carbon black in such a synthetic resin, two methods are commonly used.
A kneading machine such as a roll mill, a kneader, an intermix, a Banbury mixer, etc. can be used.

The composition of the conductive resin composition of the present invention is 100% synthetic resin.
The amount of graphite fiber is preferably 10 to 100 parts by weight, and the amount of conductive carbon black is preferably 10 to 80 parts by weight. It is desirable that the amount of graphite fiber to be blended is selected based on the properties of the graphite fiber to be used, taking into consideration the balance of electrical resistivity, processability, moldability, etc.

Furthermore, it is desirable that the amount of conductive carbon black is selected depending on the balance between electrical resistivity and processability, and the ratio of the amount of graphite fiber to conductive carbon black is 5:1 to 1:1. It is preferably within the range.

Furthermore, additives such as plasticizers, solvents, fillers, processing aids, antioxidants, and crosslinking agents can be added to the conductive resin composition of the present invention.

When the conductive resin composition of the present invention is used for molding, an appropriate method is selected from various molding methods such as extrusion molding, injection molding, 1-transfer molding, and press molding depending on the shape of the Heath resin and the molded product. A molded product can be obtained by doing this. Further, when using paint or the like, an appropriate method such as dipping, printing, spraying, etc. can be used depending on the purpose.

(Reference Example) Graphite fibers to be added to the conductive resin composition of the present invention were manufactured as follows.

Metallic iron catalyst particles with a particle size of 100 to 300 angstroms are suspended in a vertical tubular electric furnace whose temperature is adjusted to 1000 to 1100°C while hydrogen is flowing from below, and a mixed gas of Hensen and hydrogen is poured from below to this. The carbon fibers were introduced and decomposed to obtain carbon fibers having a length of 10 to 3000 μm and a diameter of 0.1 to 0.5 μm. Next, this carbon fiber was pulverized for 20 minutes at a rotational speed of 500 rpm using a planetary ball mill (Flisochu Japan Co., Ltd., P-5 type).

Next, this pulverized carbon fiber was placed in an electric furnace and maintained at 2960 to 3000°C for 30 minutes in an argon atmosphere to graphitize it to obtain graphite fibers having a diameter of 0.1 to 0.5 μm and a length of 1 to 10 μm. Ta.

〔Example〕

Ethylene vinyl acetate resin (Mitsui DuPont Chemical Co., Ltd., EVAFLEX 250, hereinafter simply referred to as EVA) was used as the synthetic resin, and graphite fiber obtained in the reference example and conductive carbon black (Lion Akzo Co., Ltd., Ketchen Black EC1, hereinafter simply referred to as EC) were used. ) and the formulation shown in Table 1 (
The mixture was kneaded for 20 minutes using two 6-inch rolls (numbers are expressed in parts by weight). Then press molding to 15
A sheet of 0x150x21111 was prepared, and sample pieces each having a length of 70 m5, a width of Ion, and a thickness of 2 mm were cut out from these sheets, and the electrical resistance value was measured using a Wheatstone bridge to calculate the volume resistivity.

The results are summarized in Table 1.

Table Compound EVA Graphite Fiber C Volume Resistivity 10-'Ω Mark 2 00 50 00 66.6 2.80 2.10 Looking at these results, it can be seen that the composition of the present invention has a significantly lower volume resistivity. I understand.

〔Effect of the invention〕

The conductive resin composition of the present invention is a lightweight composite material that uses carbonaceous conductive material instead of expensive metal fibers, and has high conductivity, so it can be used for electromagnetic shielding, etc. .

Claims (4)

[Claims] (1) 10 to 1 graphite fiber per 100 parts by weight of synthetic resin
A conductive resin composition prepared by dispersing and blending 00 parts by weight of conductive carbon black and 10 to 80 parts by weight of conductive carbon black. (2) The conductive resin composition according to claim 1, wherein the graphite fiber is graphitized vapor-grown carbon fiber. (3) The conductive resin composition according to claim 2, wherein the vapor-grown carbon fiber is obtained by contacting a hydrocarbon compound with an ultrafine metal catalyst suspended in a high-temperature zone. (4) The graphite fiber has a fiber diameter of 0.1 to 1 μm and a length of 1 μm.
The conductive resin composition according to any one of claims 1 to 3, which has a particle size of 0 μm or less.