JPS63251468A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain an electrically conductive compsn. which does not cause the deterioration of electrical conductivity by changesin environmental temp. or with time, by blending a specific master pellet obtd. by cutting a fiber into a pellet with a natural pellet composed of a thermoplastic resin. CONSTITUTION:A resin compsn. is obtd. by blending a master pellet (A), obtd. by coating an electrically conductive fiber in the form of a short fiber with a low-melting metal contg. a flux, bandling the fiber and cutting it into a pellet, with a natural pellet (B) composed of a thermoplastic resin. Examples of the electrically conductive fiber are metallic fibers such as copper fiber, stainless steel fiber, etc. and org. or inorg. fibers having a metallic (e.g., copper, aluminum) layer on the surface thereof. Examples of the flux are stearic acid, lactic acid, rosin, active rosin, etc. Examples of the low-melting metal are soldering alloys mainly composed of Sn or Sn/Pb and high-temperature soldering alloys mainly composed of Sn/Pb/Cd/Ag/Zn.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides highly reliable conductivity that has excellent conductivity and does not deteriorate even with changes in environmental temperature or changes over time. The present invention relates to a resin composition.

<Prior art> In recent years, in order to protect electronic devices from electromagnetic waves generated in external electronic circuits or to prevent electromagnetic waves from leaking from the electronic devices to the outside, the housings of electronic devices have been made of electromagnetic shielding materials. This is requested. This material for electromagnetic shielding is required to have higher electrical conductivity than conventional carbon fiber-filled materials, as well as excellent mechanical strength for the casing, so a metal-based conductive filler is used in the synthetic resin. It is essential to fill the fibers in the form of long fibers.

However, materials filled with metal-based conductive fillers in the form of long fibers can provide excellent mechanical strength and conductivity, but have the drawback of being restricted by the environment in which they are used.

In other words, if a highly active metal is used as a conductive filler, the synthetic resin will deteriorate quickly, so it cannot be used in a place that is exposed to high temperatures or direct sunlight. Since the bond with the filler is simply a contact, there is a problem in that the contact changes with changes in the environmental temperature, resulting in a decrease in conductivity. For these reasons, conventional materials filled with long fiber metal fillers have the drawback of significantly reducing reliability, which has been a major obstacle to practical application.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned drawbacks, and has excellent conductivity, and the conductivity does not deteriorate even with changes in environmental temperature or changes over time. The purpose of the present invention is to provide a highly reliable conductive resin composition that suppresses deterioration of the mechanical properties of the resin.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive research aimed at achieving the above object, the present invention has been developed to provide pellets 1 to 1 in which conductive fibers are coated with a low melting point metal containing flux. The present inventors have discovered that by using a conductive resin composition, it is possible to obtain a conductive resin composition that has excellent conductivity, does not deteriorate in conductivity even with environmental temperature changes, changes over time, etc., and has good resin physical properties. It has been completed.

That is, the present invention involves blending a master pellet made by coating long conductive fibers with a low melting point metal containing flux, cutting them into pellets, and natural pellets made of a thermoplastic resin. This is a characteristic conductive resin composition.

As the conductive fiber of the long fiber castle used in the present invention, lit
Examples include metal fibers such as fibers, copper alloy fibers, stainless steel fibers, aluminum fibers, and nickel fibers, and organic fibers or inorganic fibers having metal layers such as copper, aluminum, and nickel. The diameter of the conductive fibers is preferably about 8 to 100 μm, and 100 to 10,000 fibers are used. The blending ratio of the conductive fibers is preferably 1 to 80% by weight based on the entire composition. If it is less than 1% by weight, the conductivity will be low, and if it exceeds 80% by weight, the fluidity of the composition and the physical properties of the resin will deteriorate, which is not preferable.

51 The flux used in the present invention is preferably an organic acid-based or resin-based flux, and specific examples include organic acid-based stearic acid, lactic acid, oleic acid, glutamic acid, etc., resin-based rosin, activated rosin, etc. Depending on the low melting point metal, these may be used alone or in combination of two or more. Among fluxes, halogen- and amine-based ones are not preferred because they corrode conductive fibers and molding molds.

The blending ratio of flux is 0.1 to 5 to the low melting point metal.
Preferably, it is % by weight. Compounding amount is 0.1% by weight
If it is less than 5% by weight, the solderability of the conductive fiber is poor, and
Exceeding this is undesirable because it deteriorates the physical properties of the resin and causes corrosion and staining of the mold. The flux is mixed in a low melting point metal.

The low melting point metal used in the present invention may be any metal that has a melting point comparable to the molding temperature of the thermoplastic resin used, and Sr! Or a general solder alloy whose main component is Sn-Pb, a high-temperature solder alloy whose main component is Sn-Pb-Cd-Ag-Zn, or even a low-temperature solder whose main component is -6=Sn-pb-Cd-Bi. Examples include alloys. The blending ratio of the low melting point metal is preferably 5 to 30% by weight based on the conductive fiber.
If the amount is less than 5% by weight, it will not be sufficient to coat the conductive fibers and the conductivity will decrease, and if it exceeds 30% by weight, the low melting point metal will be liberated and the physical properties of the resin will deteriorate, which is not preferable. The low melting point metal is 0.1 to 20% of the total composition.
It is desirable to contain it in a proportion of % by weight. The low melting point metal is used by passing a long conductive fiber through the low melting point metal layer and passing it through a die to cover the outside of the conductive fiber.

Examples of the thermoplastic resin used in the present invention include polyethylene resin, polypropylene resin, polystyrene resin, acrylonitrile-butadiene-styrene resin, modified polyphenylene oxide resin, polybutylene terephthalate resin, polycarbonate resin, polyamide resin, polyetherimide resin, etc. , these may be used alone or in combination of two or more.

The conductive resin composition of the present invention can usually be manufactured as follows. This will be explained below using the drawings.

FIG. 1 is a sectional view of a master pellet 1 used in the present invention. A low melting point metal 3 filled with flux is integrally coated on the surface of the bundle of conductive fibers 2, and then cut to form a master pellet 1.

The cross section of the master pellet 1 is usually circular, but it does not necessarily have to be circular, and may be flat, oval, or other shapes depending on the situation, and is not particularly limited. This low melting point metal 3 is coated through a low melting point metal bath as shown in FIG. That is, the bundled long fiber-like conductive fibers 4
The molten low melting point metal 7 is passed through the low melting point metal bath 6 via the roll 5, and then the low melting point metal is coated on the surface of the conductive fiber via the roll 8, followed by cutting 1.
0 to produce a master pellet upper layer.

Although it is economically advantageous to carry out the process of producing master pellets continuously, it can also be carried out in a batch mode instead of continuously. The master pellets obtained in this way are
A conductive resin composition can be manufactured by blending natural pellets made only of thermoplastic resin.

The conductive resin composition of the present invention thus produced is injection molded at a temperature higher than the melting point of the thermoplastic resin to form a molded article,
It can be used as housings or parts for electronic or electrical equipment, measuring equipment, communication equipment, etc. that require electromagnetic shielding.

(Function) According to the present invention, the conductive fiber, flux, low melting point metal, and thermoplastic resin function as follows, and excellent conductivity can be obtained.

In the conductive resin composition, the conductive fibers are dispersed in the thermoplastic resin in the heating cylinder of the injection molding machine, and the low melting point metal is melted in the same way as the thermoplastic resin, so that the conductive fibers and the conductive fibers have a low melting point. The metal is coated and fused to form a network, which is poured into a mold as it is and cooled and solidified.
When the conductive fibers and the low melting point metal are fused together, the conductive fibers and the low melting point metal form a strong network in order to impart wettability to the conductive fibers with the flux.

If the wettability of the conductive fiber is poor, low melting point metals will be liberated, resulting in deterioration of the resin, deterioration of the resin's physical properties, roughening of the surface of the molded product, and a decrease in conductivity. Therefore, as in the present invention, the conductive fibers are firmly bonded to the low melting point metal to form a network, thereby significantly improving the conductivity and not impairing the physical properties of the resin. This can be confirmed by dissolving the resin component of a molded article using the conductive resin composition of the present invention in a solvent, and the network state in which the conductive fibers are bonded can be clearly confirmed. The improved conductivity allows the amount of conductive fibers to be reduced, and there is no separation or scattering of low-melting point metals, making it safer to work with.

(Examples) Next, the present invention will be explained by examples, but the present invention is not limited by the following examples.

Example 300 long copper fibers with a diameter of 50 μm were mixed with flux 2
Low melting point metals (Sn60%, PB40%) containing wt%
) The surface of the copper fiber is coated with a low melting point metal through a bath and a die, and after being integrated to a diameter of 3 nm and cooled, a length of 6 m is formed.
The pellets were cut into pieces of 1.5 m to obtain master pellets. A conductive resin composition was prepared by mechanically mixing 50 parts by weight of the master pellets and 500 parts by weight of TAFFLEX 410 (ABS resin manufactured by Mitsubishi Monsando, trade name) as natural pellets.

A molded article was obtained by injection molding using this composition, and this molded article was tested for volume resistivity, electromagnetic shielding effect, and mechanical strength.The results are shown in Table 1.
Even after an environmental test at 80°C for 3,000 hours, the volume resistivity did not change, the electromagnetic shielding effect did not deteriorate, and the mechanical strength maintained more than 80% of its initial value, demonstrating the remarkable effects of the present invention. confirmed.

Comparative Example 300 copper fibers with a diameter of about 50 μm were bundled, and on the surface,
Toughflex 410 (Mitsubishi Monsando ABS! Fat,
(trade name) was coated and integrated to a diameter of 3 ml, cooled, and cut into lengths of 6 mm to prepare master pellets. A conductive resin composition is prepared by mechanically mixing 50 parts by weight of the master pellets and 500 parts by weight of TUFLEX 410 (mentioned above) as natural pellets. A molded article was obtained by injection molding using this composition, and the properties of the molded article were tested in the same manner as in the examples.The results are shown in Table 1.

= 12- The O mark in the composition of Table 1 indicates that the component is included *1: Mitsubishi Monsanto Company, ABS resin product name No. 1
Table (Continued) V Effects of the Invention As is clear from the above explanation and Table 1, the conductive resin composition of the present invention uses conductive fibers and a low melting point metal in combination, and also contains flux. The conductive fibers are strongly bonded through the low melting point metal and have excellent conductivity, and the conductivity decreases even with environmental temperature changes and changes over time. Due to the strong bonding, the resin has excellent mechanical properties with little deterioration. High reliability can be imparted to electronic or electrical equipment by using this composition.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a pellet used in the present invention, and FIG. 2 is a conceptual diagram for explaining the manufacturing process for the pellet 1 in the present invention. 1. Upper unit... To master pellet 1, 2... Conductive fiber, 3... Low melting point metal, 4... Long fibrous conductive fiber, 5... Roll, 6... low melting point metal tank, 7... molten low melting point metal, 8... roll,
9...Coating.

Claims (1)

[Claims] 1. A master pellet obtained by coating long conductive fibers with a low-melting metal containing flux and cutting them into pellets, and a natural pellet made of a thermoplastic resin are blended. Characteristic conductive resin composition. 2. A patent claim in which the long-fiber conductive fibers are metal fibers such as copper fibers, copper alloy fibers, stainless steel fibers, aluminum fibers, nickel fibers, or organic or inorganic fibers having a copper, aluminum, or nickel layer on the surface. range 1
The conductive resin composition described in . 3 Flux contains stearic acid, lactic acid, oleic acid,
The conductive resin composition according to claim 1 or 2, which is glutamic acid, rosin, or active rosin. 4 The low melting point metal is a solder alloy whose main component is Sn or Sn-Pb, a high-temperature solder alloy whose main component is Sn-Pb-Cd-Ag-Zn, or a high-temperature solder alloy whose main component is Sn-Pb-Cd-Bi. The conductive resin composition according to any one of claims 1 to 3, which is a low-temperature solder alloy. 5 The long fibrous conductive fibers are 1% of the total composition.
The conductive resin composition according to any one of claims 1 to 4, containing the conductive resin composition in a proportion of 8% by weight. 6. The conductive resin composition according to any one of claims 1 to 5, wherein the flux is contained in a proportion of 0.1 to 5% by weight based on the low melting point metal. 7 The low melting point metal is 0.1 to 20% of the total composition.
5% by weight and based on long fibrous conductive fibers.
The conductive resin composition according to any one of claims 1 to 6, containing the conductive resin composition in a proportion of ~30% by weight.