JPS63238163A - Electrically conductive resin composition - Google Patents

Abstract

PURPOSE:To obtain the titled composition capable of keeping electrical conductivity even at high temperature, having excellent age stability and moldability and suitable for electronic apparatuses, etc., by using electrically conductive fiber in combination with a low-melting metal as electrically conductive fillers and compounding the fillers with a flux and a phosphorus-based antioxidant. CONSTITUTION:The surface of an electrically conductive filler composed of (A) electrically conductive fiber having a diameter of 8-100mum (e.g. copper filament or brass filament) (5-80wt.% based on the whole composition), (B) a low-melting metal (e.g. soldering alloy composed mainly of Sn or Sn-Pb) (5-30wt.% based on the component A) and (C) a flux (e.g. stearic acid) 0.1-5wt.% based on the component (B) is coated with (D) a thermoplastic resin (e.g. polypropylene) containing 0.1-5wt.% phosphorous-based antioxidant to obtain integrated pellets, which are chopped to form the objective composition.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Objective of the Invention] <Industrial Application Fields> The present invention is directed to a highly reliable electrical conductivity device with excellent temporal stability of electrical conductivity, particularly at high temperatures. This invention relates to a highly conductive resin composition.

(Prior art) In recent years, in order to protect electronic equipment from externally generated ff;, 117J waves or to prevent leakage of electromagnetic waves from the electronic equipment to the outside, the housings of electronic equipment have been made of electromagnetic shielding materials. is requested to do so. and,
The molding material for this shield requires higher conductivity than conventional carbon fiber-filled materials, and at the same time requires excellent mechanical strength as a casing, so a metal-based conductive filler is used. It is being carried out to fill resin with long fibers.

However, by the conventional method using the length mu of the above metal,
Although it provides excellent electrical conductivity and mechanical strength, it has the drawback of being restricted by the environment in which it can be used. However, if a highly active metal is used as a conductive filler, it will accelerate the deterioration of the synthetic resin, so the casing cannot be used in high-temperature locations or in locations that are exposed to direct external light. Since the bond between the material and the conductive filler is a mere contact, the contact changes with changes in the temperature of the environment, and as a result, there is a problem in that the conductivity of the casing gradually decreases.
For these reasons, the conventional method using long metal fibers has the disadvantage of significantly impairing reliability, which has been a major obstacle to practical application.

Next, it has been known for a long time to mix a low melting point metal and a resin to make a conductive resin composition, but the low melting point metal has poor adhesion to the resin, and when changing the material color in a molding machine, Dry punching was extremely dangerous during the molding process, as the resin and low melting point metal would separate and only the low melting point metal would fly away.

Further, in the conventional method using metal fibers, there was a problem that an oxide film was formed on the surface of the metal IIi fibers due to drying before molding, resulting in deterioration of conductivity.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and it is possible to reduce the amount of conductive fibers filled, and also to be able to withstand temperature changes in various environments. The object of the present invention is to provide a highly reliable conductive resin composition that exhibits little decrease in conductivity or change over time, retains the original characteristics of the resin, has good moldability, and molded products thereof.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive research to achieve the above object, the inventor of the present invention has developed a combination of conductive 1m fiber and low melting point metal as a conductive filler. By adding flux and phosphorus-based antioxidant to it, the conductivity does not decrease even at high temperatures, and the S-conductivity has excellent stability over time. Even during molding, the resin and low-melting point metal can separate and scatter. The present invention was completed by discovering that a highly reliable ¥4 conductive resin composition with improved molding workability can be obtained. (B) A conductive filler made of a low melting point metal and (C) a flux is coated with (D) a thermoplastic resin layer containing (E) a phosphorous antioxidant, and then cut into pellets. This is an electrically conductive resin composition characterized in that the electrically conductive TL fibers are long filamentous metal fibers, and are inorganic or organic V1 fibers having a metal layer on the surface.The low melting point metal is a general solder. , low-temperature solder, high-temperature solder, etc., a flux of 1!11I!2 type or rosin type, and a phosphorus-based antioxidant having the structural formula described below.

As the (△) conductive Ili fiber used in the present invention, 艮m@
Preferred examples include copper alloy fibers, copper alloy fibers, metal fibers such as stainless steel TiN, aluminum fibers, and nickel fibers, and organic fibers or inorganic fibers having metal layers such as copper, aluminum, and nickel on the surface. It will be done. The conductive fibers preferably have a diameter of about 8 to 100 μm,
Moreover, one in which 100 to 10,000 lines have converged is used.
The amount of conductive fibers to be blended is preferably 5 to 80% by weight based on the entire conductive resin composition. 5
If it is less than 80% by weight, the conductivity will be low, and if it exceeds 80% by weight, the fluidity and other properties of the conductive resin composition will deteriorate, which is not preferable.

The <8) low melting point metal used in the present invention is a general solder alloy containing Sn or Sn-Pb as a main component, Sn-Pb
-Cd-Aa-Zn-based high-temperature solder alloy,
Further examples include low-temperature solder alloys containing Sn-Pb-Cd-3i as a main component.

These low melting point metals may be fibrous, granular, rod-like, or linear, and are not particularly limited in shape.
In addition, low melting point metals can be used by converging male-shaped low melting point metals together with conductive fibers, converging conductive fibers whose surfaces are coated with low melting point metals, and converging bundles of converged conductive fibers into low melting point metals. Examples include coating with a melting point metal. In addition, there is also a method of sprinkling and adhering granular low-melting metal to the surface of the conductive fiber, as long as the conductive mm1 is concentrated together with the low-melting metal. The low melting point metal is desirably selected depending on the molding temperature of the thermoplastic resin covering the conductive filler.

More preferably, a low melting point metal is selected and used, which has a melting point that melts at the highest temperature region of the heating cylinder of the injection molding machine. It is desirable that the low melting point metal be contained in an amount sufficient to bond and cover the conductive m-fibers, that is, in a proportion of 5 to 30 In% to the conductive m-fibers. If the content is less than 5% by weight, binding and coating of the conductive fibers will be insufficient, and if it exceeds 30% by weight, only the low melting point metal will be liberated and the physical properties of the resin will deteriorate, which is not preferable. be.

The flux (C) used in the present invention includes organic acid-based,
Resin-based fluxes are preferred, and specific examples include organic acids such as stearic acid, lactic acid, oleic acid, and glutamic acid, resin-based rosins, and activated rosins, which may be used alone or in combination of two or more. use. It is not preferable to use halogen-based or amine-based fluxes because they corrode conductive fibers, molds, etc. It is desirable that the blending ratio of flux be 0.1 to 5% by weight relative to the low melting point metal. If the content is less than 0.1% by weight, it has no effect on the solder wettability of the conductive fibers, and if it exceeds 5% by weight, the physical properties of the gold and resin deteriorate, and the mold becomes corroded and stained, which is not preferable. It is usually preferable to fill a low melting point metal with flux.

Examples of the phosphorus antioxidant (D) used in the present invention include those having the following structural formula.

IHCA (Sanko Kagaku Co., Ltd., trade name) MARK PEF'24 MARK PEP36 MARK 329K MARK 1178 R=C, alkyl group of 2 to Cps (manufactured by Adeka Argus Co., Ltd., trade name) MARK
It is desirable that the 1500 phosphorus antioxidant is contained in a proportion of 0.1 to 5% by weight based on the thermoplastic resin. When the blend m is less than 0.1% by weight, the conductive IJi
It is not preferable because it is insufficient to remove the oxide film of IIf and has poor solder wettability, and when it exceeds 5% by weight, physical properties such as a decrease in the heat distortion temperature of the resin are undesirable. It is desirable that the phosphorus antioxidant be blended into the resin of the thermoplastic resin layer, which will be described later.

The resin for the thermoplastic resin layer (E) used in the present invention is as follows:
Polypropylene resin, polyethylene resin, polystyrene resin, acrylonitrile butadiene styrene resin,
Examples include modified polyphenylene oxide resin, polybutylene terephthalate resin, polycarbonate resin, polyamide resin, polyetherimide resin, etc.
Use seeds or a mixture of two or more.

The conductive resin composition of the present invention is manufactured by a conventional method. This will be explained below using the drawings.

FIGS. 1(a) to 1(d) are sketches of a conductive filler in which conductive fibers and low-melting point metals are aggregated.

That is, as shown in FIG. 1(a), a certain number of fibrous low-melting point metals 3 containing flux are added to and assembled into a bundle of conductive fibers 2 to form a conductive filler 2. In addition, the collection of conductive m-line and low melting point metal is
As shown in FIG. 1(b), conductive fibers 2 coated with a low melting point metal 3 may be assembled together, or as shown in FIG. It can be coated with gold a3 or coated with conductive IJil as shown in Figure 1<d).
! A conductive filler 2 is obtained by adhering and aggregating granular low-melting point metal 3 on the surface of the filler 2. A thermoplastic resin layer 4 containing a phosphorous antioxidant is integrally coated on the surface of the conductive filler 19, and cut into pellets of the conductive resin composition. FIG. 1 (A) showing a cross-sectional view of the pellet 10
~(D) shows the conductive filler 1 in FIGS. 1(a) to (d).
d) respectively. That is, conductivity 1
! A thermoplastic resin 4 containing a phosphorous antioxidant is integrally coated on the surface of a conductive filler 1 made of fibers and a low melting point metal. The cross section of the berette is usually circular, but the cross section may be flat or other shapes, and the shape is not particularly limited. As shown in Figure 2, the pellets are
Conductive filler 11 assembled as shown in FIGS. 1(a) to (d)
A thermoplastic resin 14 is coated and integrated on the surface of the conductive filler 11 through a die 13 of an extruder 12, and then cutting 15 is performed to form pellets 16. Although it is economically advantageous to carry out the pellet manufacturing process continuously, it is not necessarily necessary to carry out the pellet manufacturing process continuously, and the pellet manufacturing process may be performed in a batch manner. The conductive resin composition thus obtained can be injection molded at a temperature higher than the melting point of the low-melting point metal to form molded products for housings and parts of electronic devices, measuring instruments, communication devices, etc. that require electromagnetic shielding. can.

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

That is, in the process of conductive resin composition being dispersed in thermoplastic resin in the heating cylinder of an injection molding machine, and being injected into the mold and cooled and solidified, the low melting point metal melts in the same way as the thermoplastic resin. Well, conductive 11i! The conductive mu and the conductive fibers form a network due to the low melting point metal covering and fusing, and are cooled and solidified as they are.

When conductive 411 and a low melting point metal are fused together, the oxide film of the conductive fibers formed during the manufacturing process or during drying is removed by the reducing action of the phosphorous antioxidant, resulting in improved wettability to the flux. , the conductive fibers and the low melting point metal form a strong network.

If an oxide film remains on the conductive material 814 or the wettability of the conductive fibers is poor, corrosion of the conductive fibers and release of low melting point metals will occur, reducing the physical properties of the resin and also worsening the conductivity. . The conductive fibers and 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 the molded product with a solvent and confirming the network state in which the conductive fibers are combined.

This improvement in conductivity makes it possible to reduce the amount of conductive fibers, and also eliminates the separation and scattering of low-melting point metals, making it safer to work with.

(Example) Next, the present invention will be explained by examples.

Example 300 long pieces of copper II with a diameter of about 50 μm and one long piece of low melting point metal (60% Sn, 40% Pb) with a diameter of about 300 μm containing 2% by weight of flux were collected and converged to conduct electricity. It was used as a filler. MA on the surface of conductive filler
RK PEP24 (manufactured by Adeka Argus Chemical Co., Ltd., phosphorus-based antioxidant trade name) Tuflex 410 containing 2% double weight (manufactured by Mitsubishi Monsanto Chemical Co., Ltd., ABS resin, trade name)
The coating is integrated through the die of the extruder, and after cooling,
The fibers were cut to produce a conductive resin composition with a diameter of 3 fibers and a length of 6 m.

A molded article was obtained by injection molding using this composition, and the volume resistivity, electromagnetic shielding effect, and mechanical strength of this molded article were tested. The results are shown in Table 1. Even after 3,000 hours of environmental testing at 80°C, the molded product remained
The shielding effect did not deteriorate at all, and the mechanical strength also maintained 80% or more of its initial value, confirming the extremely remarkable effects of the present invention.

Comparative Example In the example, a conductive resin composition having a diameter of 3 fibers and a length of 6n+m was produced in the same manner as in the example except for the low melting point metal, flux, and phosphorus antioxidant. Molded articles were obtained using this conductive resin composition in the same manner as in the examples, and the same characteristic tests were conducted. The results are shown in Table 1.

The O mark in the composition of Table 1 indicates that the component is included *1: Manufactured by Adeka Argus Chemical Co., Ltd., product name *2 2 Manufactured by Mitsubishi Monsanto Co., Ltd., ABS resin product name Table 1 (Continued) [Invention [Effect] As is clear from the above explanation and Table 1, the conductive resin composition of the present invention contains conductive U &
By using a combination of fiber and a low-melting point metal, as well as a flux and a phosphorus-based antioxidant, the conductive fibers have good wettability, and the conductive fibers are firmly bonded to each other by the low-melting point metal, making them suitable for high-temperature environments. The conductivity does not deteriorate even with changes, and the shielding effect has excellent stability over time.

Furthermore, since the resin has excellent electrical conductivity, it is possible to reduce the amount of the electrically conductive filler to be filled, and furthermore, the inherent physical properties of the resin can be maintained. Because the low melting point metal is firmly bonded to the conductive fibers, there is no separation or scattering of the low melting point metal, making it safe and improving moldability. The molded product of the present invention using this conductive resin composition can be used in electronic devices,
When used in measuring equipment, communication equipment, etc., it can provide extremely high reliability.

[Brief explanation of the drawing]

Figures 1 (a) to d) are perspective views showing the conductive filler of the present invention, Figures 1 (a) to 2) are cross-sectional views of the pellets of the present invention, and Figure 2 is the pellets of the present invention. FIG. 3 is a conceptual diagram for explaining the manufacturing process. 1.11... Conductive filler, 2... Conductive fiber,
3...Low melting point metal, 4,14...Thermoplastic resin layer, 10.16...Pellet. (α) (A) 1. Indication of the case Patent Application No. 71570 of 1988 21 Name of the invention Conductive resin composition 3. Person making the amendment Relationship to the case Patent applicant (shipment date June 30, 1988) (Japanese) "Figure 1" 7. Contents of the amendment (1) "(a) to (2)" on page 13, line 15 of Meiji HJ are amended to "(e) to (h)" . (2) In lines 1 and 2 of page 21 of the specification, "(a) or 2)" is amended to "(O) or h)". (3) For the subdivision number in Figure 1 of the drawing, (a) is changed to (+3), (b) is changed to (f), and (c) is <(
+ ) and (d) to (h), respectively, in red. As shown in the attached sheet ((1) (,2,) 19861
February 4th 3, Relationship with the case of the person making the amendment Patent applicant 3-3 Shinbashi, Minato-ku, Tokyo @ No. 9 6 Number of inventions increased by the amendment 08 Contents of the amendment (1) Scope of claims Attachment (2) Delete r-Cd J on page 7, line 5 of the specification. (3) Delete r-Cd J on page 7, line 6 of the specification. (4) From page 7, line 20 to page 8, line 2 of the specification, ``More preferably, a low melting point metal is selected and used that has a melting point that melts at the highest temperature part of the heating cylinder of the injection molding machine.''"is to be done." is deleted. (5) On page 16, line 19 of the specification, next to "Do not show," wash the molded product with methylene chloride, dissolve the resin, and examine the network state of the remaining conductive fibers using an electron microscope. I took a photo, which is shown in Figure 3. In the figure, it can be seen that the conductive fibers 20 and the conductive m-fibers 21 are firmly fused and bonded by the low melting point metal 22. Add 1. (6) From page 20, line 20 to page 21, line 7 of the specification, “Figure 1 (a) to 16...Berrett” is replaced with “Figure 1 (a)”. 1 (e) to d) are perspective views showing the conductive filler in the present invention, and FIGS. 1(e) to 1h)
2 is a conceptual diagram for explaining the manufacturing process of the pellet in the present invention, and FIG. 3 is a cross-sectional view of the pellet in the present invention. FIG. 3 is a cross-sectional view of the pellet in the invention. 2 is an electron micrograph showing the shape of conductive Pa fibers fused to. 1.11... Conductive filler, 2,20°21...
Conductive fiber, 3.22...Low melting point metal, 4.14.
...Thermoplastic resin layer, 10.16...Bellet,"
and correct it. (7) Claim 1 characterized by FIG. 3 of the attached sheet after FIG. 2 of the drawing. , (D) A conductive resin composition comprising (E) a thermoplastic resin layer containing a phosphorous antioxidant, which is integrally coated and cut into ζit pellets. 2 The conductive fibers are long-fiber copper fibers, yellow FFJ fibers,
The conductive resin composition according to claim 1, which is stainless steel fiber, aluminum fiber, nickel fiber, or organic or inorganic fiber having a metal layer on the surface. 3. The conductive resin composition according to claim 1 or 2, wherein the low melting point metal is mainly Sn or Sn-Pb. 4 Flux contains stearic acid, lactic acid, oleic acid,
The conductive resin composition according to any one of claims 1 to 3, which is glutamic acid, rosin, or active rosin. 5 The conductive fiber has a content of 5 to 80% relative to the conductive resin composition.
The conductive resin composition according to any one of claims 1 to 4, wherein the conductive resin composition is contained in a proportion of % by weight. 6 The low melting point metal is 5 to 30'YJ to the conductive fiber.
The conductive resin composition according to any one of claims 1 to 5, which contains L in an amount of %. 7. The conductive resin composition according to any one of claims 1 to 6, wherein the flux is contained in a proportion of 0.1 to 5% by weight based on the low melting point metal. 8 Phosphorous antioxidant is 0.0% relative to thermoplastic resin.
The conductive resin composition according to any one of claims 1 to 7, containing the conductive resin composition in a proportion of 1 to 5% by weight. Figure 3 Procedural amendment (voluntary) March 16, 1988

Claims (1)

[Claims] 1. On the surface of a conductive filler consisting of (A) conductive fibers (B) a low melting point metal and (C) flux (D)
A conductive resin composition characterized in that it is cut into pellets formed by integrally forming a coating with (E) a thermoplastic resin layer containing a phosphorus-based antioxidant. 2. The conductive fiber according to claim 1, wherein the conductive fiber is a long fiber copper fiber, brass fiber, stainless steel fiber, aluminum fiber, nickel fiber, or an organic or inorganic fiber having a metal layer on the surface. Resin composition. 3 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 claim 1 or 2, which is a low-temperature solder alloy. 4. The conductive resin composition according to claim 1, wherein the 4 flux is stearic acid, lactic acid, oleic acid, glutamic acid, rosin, or activated rosin. 5. Claims 1 to 4, wherein the conductive fiber is contained in a proportion of 5 to 80% by weight based on the conductive resin composition.
2. The conductive resin composition according to any one of Items 1-1. 6. The conductive resin composition according to claim 1, wherein the low melting point metal is contained in a proportion of 5 to 30% by weight based on the conductive fibers. 7 flux is 0.1 to 5% by weight based on the low melting point metal
The conductive resin composition according to any one of claims 1 to 6, containing the conductive resin composition in a proportion of . 8 Phosphorous antioxidant is 0.1 to 0.1 to thermoplastic resin
The conductive resin composition according to any one of claims 1 to 7, containing 5% by weight.