JPH0277442A - Electrically conductive thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain an electrically conductive thermoplastic resin composition having retained mechanical strength and surface smoothness and excellent electromagnetic wave shielding properties and electrostatic prevention by blending a thermoplastic resin with a specific amount of carbon black or graphite powder and carbon fiber produced by vapor phase method. CONSTITUTION:The aimed resin composition obtained by blending a thermoplastic resin (e.g., polyolefin resin or styrene based resin) with (A) A1: 5-20wt.% carbon black (e.g., acetylene black or channel black) or graphite (e.g., natural graphite) and A2: 1-40wt.% vapor phase method-manufactured carbon fiber, produced by substrate method or floating method and having preferably 0.1-1mum diameter and preferably 0.1-1mum length or (B) B1: 0.5-5wt.% electrically conductive carbon black (e.g., super conductive furnace or conductive furnace) and B2: 1-30wt.% vapor phase carbon fiber similar to the component A2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conductive thermoplastic resin composition that is excellent in shielding electromagnetic waves and preventing static electricity.

(Prior Art) It is known to impart conductivity to a thermoplastic resin by uniformly dispersing PAN-based or pinch-based carbon fibers, carbon black, or graphite.

However, when PAN-based or pitch-based carbon fibers are blended into thermoplastic resin, there is not much of a decrease in mechanical strength, but there are problems with surface smoothness, and a reproducible specific resistance value is imparted to the resin composition. It's hard to do. On the other hand, when carbon black or graphite is blended into a thermoplastic resin, the surface smoothness is not a problem, but the mechanical strength is reduced.

Furthermore, the biggest drawback of resin compositions that have been imparted with electrical conductivity by blending carbon black or graphite alone is that it is difficult to impart reproducible specific resistance values to the resin composition (this is what the invention seeks to solve). Issue) If carbon black or graphite is blended at a high filling rate of, for example, 40% by weight or more, the desired high electrical conductivity can be obtained, but blending at such a high filling level will only result in a decrease in mechanical strength. First, there is no improvement in conductivity commensurate with the amount exceeding this level.

Furthermore, when carbon black or graphite and PAN-based or pitch-based carbon fibers are blended into a thermoplastic resin, there is a drawback that the surface smoothness of the molded product is impaired.

An object of the present invention is to provide a conductive thermoplastic resin composition which has excellent mechanical strength and surface smoothness, has high conductivity, and is effective in shielding electromagnetic waves and preventing static electricity.

(Means for Solving mg) As a result of intensive research to achieve the above object, the present inventor has discovered that a thermoplastic resin contains a predetermined amount of carbon black or graphite powder, or conductive carbon black and vapor grown carbon. The present invention was completed by discovering that by blending fibers, a molded article that maintains mechanical strength and surface smoothness and stably exhibits the desired electrical conductivity can be obtained.

That is, the gist of the present invention is a conductive thermoplastic resin composition comprising a thermoplastic resin containing 5.0 to 20.0% by weight of carbon black or graphite powder and 1.0 to 40% by weight of vapor-grown carbon fiber. and a conductive thermoplastic resin composition comprising a thermoplastic resin containing 0.5 to 5.0% by weight of conductive carbon black and 1.0 to 30% by weight of vapor-grown carbon fiber.

Hereinafter, one aspect of the present invention will be explained in detail.

Carbon black and graphite used in the present invention include:
Examples include acetylene black, channel black, furnace black, natural graphite, and artificial graphite.
One type or two or more types of these can also be used.

Conductive carbon blacks include super conductive furnaces (S, C, F), conductive furnaces (C, F), and extra conductive furnaces.
Conductive Furness (X.

C, F), etc., and one or two of these
More than one species can also be used.

It is preferable to use carbon black, conductive carbon black, and graphite with a small particle size and a well-developed structure in order to improve monodispersity and fluidity. For conductive carbon black, for example, furnace black One type, Ketchen Black, is particularly preferred.

The blending amount of carbon black or graphite is within the range of 5.0 to 20.0% by weight in the composition from the viewpoint of imparting conductivity and improving mechanical properties. It is within the range of 0.5 to 5.0% by weight. If the blending amounts are less than 5.0% by weight and 0.5% by weight, respectively, a cohesive structure sufficient to impart electrical conductivity will not be formed in the resin, making it impossible to improve electrical conductivity.

On the other hand, if they are used in amounts exceeding 20% by weight and 5.0% by weight, respectively, the electrical properties will improve, but the mechanical properties will tend to deteriorate markedly. The goal is to obtain a composition with excellent physical properties.

In the present invention, in addition to ordinary carbon black,
Conductive carbon black is used, and the latter is more preferred because it has high conductivity and can improve electrical properties even in small amounts.

The reason why the upper limit of the amount of conductive carbon black added is low is that the surface layer has a graphite structure, unlike carbon black, which has extremely poor conductivity due to the amorphous structure found in ordinary carbon black even when added in a small amount. This is because the current propagation is good due to the well-developed cohesive structure.

The vapor grown carbon fiber used in the present invention is produced using a substrate method.

Vapor-grown carbon fibers produced by either the floating method or the floating method can also be used. For example, carbon fibers described in JP-A-60-27700 and JP-A-62-78217 can be mentioned.

It also includes carbon fibers made by these methods that have been treated at high temperatures of 2000°C or higher.

The vapor grown carbon fiber used in the present invention has a diameter of 0. 1-1
μm, length 1.0 μm to 1. omm is preferred.

The amount of vapor-grown carbon fiber used in combination with carbon black or graphite is 1.0 to 40% by weight in the composition, depending on the target degree of conductivity.

In the case of conductive carbon black, it ranges from 1.0 to 30% by weight.

This blending amount is 1. If it is less than 0% by weight, an aggregated structure sufficient to impart conductivity will not be formed in the resin, and therefore almost no effect can be expected when used in combination with carbon black or conductive carbon black.

On the other hand, the upper limit of each compounding amount is 40% by weight.

If it exceeds 30% by weight, the fluidity during melting is good with only vapor grown carbon fiber and resin, but when used in combination with carbon black, graphite, and conductive carbon black, the fluidity deteriorates and it is difficult to mold. becomes. Also, even if blended at a high filling rate exceeding these upper limits, high conductivity will be maintained, but even if blended at such a high filling rate level, the conductivity will not improve commensurately with the amount exceeding the level. I can't see it.

The thermoplastic resin used in the present invention is basically not limited, and resins used in the molding field can be effectively used, including polyolefin resins such as polyethylene and polypropylene, polystyrene, ABS, A] f
Styrenic resin such as tJJ, nylon 6, nylon 6
6. Polyamide resin such as nylon 12, polyethylene terephthalate.

These include engineering plastics such as polybutylene terephthalate resin, polyacetal, polyphenylene sulfide, polysulfone, polyetherketone, and polyethersulfone.

These thermoplastic resins can be used alone or in combination of two or more types, and various commonly used additives such as lubricants, Plasticizers, stabilizers, etc. may be added in advance.

Any method may be used to blend carbon black, conductive carbon black, or graphite and vapor grown carbon fiber into the thermoplastic resin.

A mixing method of uniformly kneading in a conventional manner using an appropriate blender such as a Banbury mixer, a kneader, or a Henschel mixer can be freely adopted.

The present invention has excellent surface smoothness by blending carbon black etc. and vapor grown carbon fibers into a thermoplastic resin.
The reason for this is thought to be as follows.The molded product is highly conductive.

This is a characteristic of vapor grown carbon fiber. (b) Large aspect ratio.

(b) Since the fibers are fine, agglomerated structures tend to develop in the molded product.

(c) Large surface area.

It is thought that the various properties that contribute to conductivity, such as, synergistically improve the propagation of current, and that the combination of carbon black, etc. and vapor-grown carbon IR fibers contributes to improving the conductivity of the composition. . The present invention will be specifically explained below with reference to Examples.

(Example 1 and Comparative Example 1) Polypropylene resin (5MA410 manufactured by Showa Denko K.K.)
, carbon black (11! Kandenka Black manufactured by Ki Kagaku Kogyo Co., Ltd.), and vapor grown carbon fiber (produced by the floating method using ferrocene as a catalyst and benzene as a raw material) in the proportions shown in Table 1 and melted. Pellets were obtained by kneading. Most vapor grown carbon fibers have a diameter of 0.1 to 1 μm and a length of 1 μm or more.
It is 2 mm.

Next, the obtained pellets were molded under the usual molding conditions for polypropylene resin.

The electrical properties of each test piece obtained were measured using a surface resistance meter manufactured by Mitsubishi Yuka Co., Ltd.

The results are shown in Table 1 along with comparative examples.

As is clear from the volume resistivity values shown in Table 1, excellent conductivity and moldability were obtained by using carbon black and vapor-grown carbon fiber in combination. In addition, Examples (1-1 to 1-
3) had good surface smoothness.

(Example 2 and Comparative Example 2) Same as Example 1 except that graphite fine powder (UFG-2 manufactured by Showa Denko K.K.) was blended in the proportion shown in Table 2 instead of the carbon black of Example 1. A molded product of polypropylene resin was obtained under these conditions.

The electrical characteristics of each test piece obtained were measured using a surface resistance type manufactured by Mitsubishi Yuka Co., Ltd.

The results are shown in Table 2 together with comparative examples.

As is clear from the volume resistivity values shown in Table 2,
Excellent conductivity was obtained by using graphite and vapor-grown carbon fiber together. In addition, all of Examples (2-1 to 2-2) had good surface smoothness.

(Examples 3 to 8 and Comparative Examples 3 to 8) Polypropylene resin (SMA-410 manufactured by Showa Denko Co., Ltd.)
), Ketchen Black (Ketchen Black 600JD manufactured by Lion Akzo Co., Ltd.), vapor-grown carbon fiber (same as above, produced by the floating method using ferrocene as a catalyst and benzene as a raw material).

They were blended in the proportions shown in Table 3 and melted and kneaded to obtain pellets. Next, the obtained pellets were molded under conventional polypropylene resin molding conditions, and the electrical properties of each test piece obtained were measured using a surface resistance model manufactured by Mitsubishi Yuka Co., Ltd.

The results are shown in Table 3 along with comparative examples.

As is clear from the volume resistivity and moldability shown in Table 3, excellent conductivity and moldability were obtained by using Ketchen Black and vapor-grown carbon fiber in combination. Also, Example 3
-8 had good surface smoothness.

(Effects of the Invention) According to the present invention, it is possible to provide a resin composition that provides molded articles with high mechanical strength, excellent surface smoothness, and can reproduce any desired conductivity, and its industrial value is great. be.

(Margin below)

Claims (4)

[Claims] (1) 5.0-20.0% by weight of carbon black and 1
．． A conductive thermoplastic resin composition comprising a thermoplastic resin containing 0 to 40% by weight of vapor-grown carbon fiber. (2) A conductive thermoplastic resin composition comprising a thermoplastic resin containing 0.5 to 5.0% by weight of conductive carbon black and 1.0 to 30% by weight of vapor-grown carbon fiber. (3) A conductive thermoplastic resin composition comprising a thermoplastic resin containing 5.0 to 20% by weight of graphite powder and 1.0 to 40% by weight of vapor-grown carbon fiber. (4) The conductive carbon black is at least one type selected from super conductive furnace (S.C.F), conductive furnace (C.F), and extra conductive furnace (X.C.F). The conductive thermoplastic resin composition according to claim 2, which is carbon black.