JPS63235368A - Electrically conductive resin composition and molded product thereof - Google Patents

Abstract

PURPOSE:To provide the title compsn.which scarcely causes lowering or change in electrical conductivity with time and has excellent moldability and reliability, consisting of a specific master pellet and a thermoplastic pellet. CONSTITUTION:An electrically conductive filler 11 obtd. by coating 0.5-30wt.% electrically conductive fiber (a) having a diameter of 8-100mum (e.g., copper fiber) with 5-30wt.% [based on the amount of the component (a)] low-melting metal (b) (e.g., soldering alloy mainly composed of Sn or Sn/Pb) and 0.1-5wt.% [based on the amount of the component (b)] flux (c) (e.g., stearic acid) is extruded through the die 13 of an extruder 12 to coat the filler with a thermoplastics (e.g., PP) contg. 0.1-5wt.% phosphate antioxidant. The resulting filler is cut (15) to obtain a master pellet 16 having a component (a) content of 5-80wt.%. the master pellet 16 is blended with a thermoplastic pellet (e.g., polycarbonate).

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides a highly reliable device that has excellent conductivity and has little decrease in conductivity even when placed in various environments. The present invention relates to a conductive resin composition and a molded article thereof.

(Prior Art) In recent years, in order to protect electronic devices from electromagnetic waves generated in electronic circuits or to prevent leakage of electromagnetic waves to the outside, there has been a demand for casings of electronic devices to be made of electromagnetic shielding materials. The molding material for this shield requires higher conductivity than the conventional one filled with carbon 1JAN, and at the same time requires excellent mechanical strength as a casing. Filler length 11
Filling with resin in crude form is practiced.

However, by the conventional method using long metal fibers,
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. In other words, if a highly active metal is used as a conductive filler, it will accelerate the deterioration of the synthetic resin, resulting in the disadvantage that the casing cannot be used in high-temperature locations or in locations exposed to direct external light. Since the bond with the conductive filler is a mere contact, the contact changes with changes in the concentration of the environment, and as a result, there is a problem that the 1-meter property of the casing gradually decreases.
For these reasons, the conventional method using the metal long 11 navy blue 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 an S conductive resin composition, but the low melting point metal has poor adhesion to the resin, and when changing the color of the molding material. When the molding machine was blank-shot, the resin and low-melting point metal separated and only the low-melting point metal was scattered, which was extremely dangerous for the molding process.

Further, in the conventional method using gold 8 fibers, there was a problem that an oxide film was formed on the surface of the metal fibers due to drying before molding, resulting in poor 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 slightly reduce the amount of conductive fibers filled, and also to be able to withstand changes in concentration in various environments. The object of the present invention is to provide a highly reliable conductive resin molded product with good molding processability, which exhibits little decrease in conductivity or change over time, and retains the original characteristics of the resin.

[Structure of the Invention] (Means for Solving the Problems) As a result of extensive research aimed at achieving the above object, the present inventor has discovered that conductive fibers, low melting point metals, and flux are used as conductive fillers. The present invention has been completed by discovering that a molded article that achieves the above objectives can be obtained by using a conductive resin composition that uses a thermoplastic resin that is used in combination with a phosphorus antioxidant. . That is, the present invention comprises (A) a conductive fiber, (B) a low melting point metal, and (
C) On the tension surface of the 81 conductive filler made of flux, (D
) A conductive resin composition characterized by blending (E) a pellet-shaped master pellet integrally coated with a thermal 11iJI resin layer containing a phosphorous antioxidant, and (F) a thermoplastic resin pellet. It is. The present invention is also a conductive resin molded article, which is obtained by injection molding this conductive resin composition at a concentration equal to or higher than the melting point of a low-melting point metal.

(A) Electric conductivity [H used in the present invention is preferably a long fiber type, such as copper fiber, copper alloy fiber, stainless steel 1L
Examples include metal fibers such as lft, aluminum fibers, and nickel fibers, and organic fibers or inorganic fibers having a metal layer of copper, aluminum, nickel, etc. on the surface. The conductive mwlI preferably has a diameter of about 8 to 100 μm, and has 100 to 10,000 converged conductive mwlI.

The content of the conductive fibers is preferably 0.5 to 30% by weight based on the entire conductive resin composition.

If it is less than 0.5% by weight, the conductivity will be low, and if it exceeds 30% by weight, the fluidity and other properties of the conductive resin composition will deteriorate, which is not preferable. The amount of conductive fiber blended in the master pellet is preferably 5 to 80% by weight.

The low melting point metal (B) used in the present invention is a general solder alloy containing Sn or 5n-Pb as a main component, Sn-
Examples include an a-temperature solder alloy whose main component is Pb-Cd-Aa-Zn, and a low-humidity solder alloy whose main component is Sn-Pb-Cd-S+. These low melting point metals may be in the form of TLTN, powder, rod, or wire, and are not particularly limited in shape. In addition, low melting point metals can be used by converging fibrous low melting point metals within conductive fibers, by coating the surface of conductive fibers with low melting point metals, or by lowering the entire converged conductive fibers. Examples include coating with a melting point metal.

In addition, there is a method of sprinkling and adhering granular low-melting metal to the surface of the conductive fibers, as long as the conductive fibers and the low-melting metal are concentrated together.

The low melting point metal is a thermoplastic resin that coats the conductive filler,
It is also desirable to select according to the molding concentration of the thermoplastic resin, which is a natural pellet. More preferably, a low melting point metal is selected and used which has a melting point that melts at the highest concentration area 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 fibers, that is, in a proportion of 5 to 30% by weight based on the conductive fibers.

If the content is less than 5% by weight, it will be insufficient to bind and coat the conductive fibers, 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 undesirable. be.

The (C)7 lux used in the present invention includes organic acids,
Resin-based 7lux is preferred, and specific examples include organic acid-based stearic acid, lactic acid, oleic acid, glutamic acid, etc., resin-based rosin, activated rosin, etc., and these may be used alone or in combination of two or more. and use it. Halogens, amines, etc. corrode conductive fibers, molds, etc., so their use is not preferred.

The blending ratio of flux is 0.1 to low melting point metal.
It is desirable to set the weight to 5%. If the content is less than 0.1% by weight, it has no effect on the solderability of the conductive fibers, and if it exceeds 5% by weight, the physical properties of the resin deteriorate and the mold becomes corroded and stained, which is not preferable. It is preferable that the slack is normally filled with a low melting point metal.

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

(Sanko Kagaku Co., Ltd., trade name) MARK PEP24 MARK PEP36 MARK 329K MARK 1178 R=C, alkyl group of 2 to CI5 (manufactured by Adeka Argus Co., Ltd., trade name) MARK
The blending amount of the 1500 phosphorus antioxidant is preferably 10.1 to 5% by weight based on the thermoplastic resin. If the amount is less than 0.1% by weight, it will be insufficient to remove the oxide film from the conductive fibers and the solder wettability will be poor, and if it exceeds 5% by weight, the thermal deformation concentration of the resin will decrease, resulting in decreased physical properties. 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, and the like.

The above components, that is, conductive fibers and low melting point metals including flux, are assembled to form a conductive filler, and a thermoplastic resin containing a phosphorous antioxidant is coated and integrated on the surface of the conductive filler. Cut into master pellets.

The (F) thermoplastic resin pellets (hereinafter referred to as natural pellets) used in the present invention may be the same or the same as the resin of the above-mentioned (L) thermoplastic resin layer, or may be different. Alternatively, the third synthetic resin formed at the interface by mixing with the thermoplastic resin (E) may have a reinforcing effect, that is, it may be a blended polymer. For example, when (E) a modified PPO resin, polycarbonate resin, etc. is used as the thermoplastic resin, good results can be obtained if a styrene-based thermoplastic resin is used as the natural pellet.

By doing so, the third synthetic resin formed at the interface has a reinforcing effect. By using these combinations, molded products with excellent properties can be obtained.

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 long fibrous 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 aggregated into a bundle of conductive fibers N2 to form a mass on the conductive filler. In addition, the aggregation of conductive fibers and low melting point metals is
As shown in FIG. 1(b), conductive fibers 2 coated with a low melting point metal 3 are assembled on the surface, or as shown in FIG. The conductive IIM 2 is coated with metal 3 or, as shown in FIG. 1(d), granular low-melting point metal 3 is adhered and aggregated on the surface of the conductive IIM 2 to form a conductive filler. The master pellets 10 shown in FIGS. 1(a) to 1(d) are produced by coating the surface of the conductive filler with a thermoplastic resin layer 4 containing a phosphorous antioxidant and cutting the resin layer 4. Figures 1 (a) to (d), which are cross-sectional views of the master pellet, show the conductive filler 1 shown in Figures 1 (a) to (d), which is a collection of conductive fibers and low-melting metal.
These are shown in correspondence with each other.

The master pellet 10 usually has a circular cross section, but
It may be flat or other shapes, and the shape is not particularly limited.

As shown in Fig. 2, the master pellet is as shown in Fig. 1 (
The conductive filler 11 assembled in a) to (d) is passed through the die 13 of the extruder 12 to form a coating with thermoplastic resin on the surface of the 1 m filler 11, and then cut 1.
5 to obtain a master pellet 16. Although it is economically advantageous to carry out the master pellet production process continuously, it is not necessarily necessary to carry out the process continuously, and the production may be carried out in a batch manner. A conductive resin composition is prepared by blending natural pellets with the master pellets in a conventional manner.

For the natural pellets to be blended, the type and amount of thermoplastic resin are appropriately selected depending on the characteristics required of the conductive resin composition and its molded product.

The conductive resin composition thus produced can be injection molded at a concentration higher than the melting point of the low melting point metal to form molded products for housings and parts of electronic equipment, measuring equipment, communication equipment, etc. that require electromagnetic shielding. can.

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

In other words, the conductive resin composition is produced by dispersing conductive fibers into a thermoplastic resin in a heating cylinder of an injection molding machine.
In the process of injecting into the mold and cooling and assimilating it, the low melting point metal melts and fuses with the conductive fibers, and the conductive fibers form a network with the low melting point metal, which is then cooled and solidified.

When the conductive fiber and the low melting point metal are fused together, the oxidized layer of conductive IIH formed during the manufacturing process or during drying is removed by the reducing action of the phosphorous antioxidant, giving it wettability to the flux. To achieve this, the conductive fibers and low-melting metal form a strong network. If an oxide film remains on the conductive mM or the wettability of the 81 conductive iI material is poor, corrosion of the conductive cord and release of low melting point metals will occur, reducing the physical properties of the resin and reducing the conductivity. It also gets worse. 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. 13 like this!
By improving the properties, the amount of conductive IIH can be reduced, and there is no separation or 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 navy blue with a diameter of 50 μm and 2 pieces of rosin.
Straight 4% 300 μm long Sn − with heavy weight % Kanakura
One piece of Pb solder (3N60%, Pb40%) was assembled and converged to form a conductive filler. Table of conductive filler imk: MAf<K Tufflex 410 (ABS manufactured by Mitsubishi Monsanto Chemical Co., Ltd.) containing 2% by weight of PEP24 (manufactured by Argus Chemical Co., Ltd., phosphorus antioxidant trade name)
Resin (product name) is integrated into a coating using an extruder die,
After cooling, it was cut into master pellets. This master pellet had a diameter of 3 m111 and a size of 6 Ill11. This master pellet to Offiffi section contains 50 natural pellets (Tufflex 410 mentioned above)
A conductive resin composition was prepared by mechanically mixing 0 parts by weight. The filling rate of copper fibers in this case was 10% by weight. Using this conductive resin composition, injection molding was performed at a concentration higher than the melting point of the low melting point metal to obtain a molded article. The obtained molded product was tested for volume resistivity, shielding effect, bending strength, and isot impact strength, and the results are shown in Table 1. Even after heating at 80° C. for 3000 hours, the shield hardening did not decrease at all, and the mechanical strength maintained 83% or more of its initial value, confirming the extremely remarkable effects of the present invention.

Comparative Example 1 meter of long copper fiber 300 wood with a diameter of about 50 μm was coated with Tuflex 410 (described above) using a die of an extruder, and after cooling, it was cut to produce master pellets. ``This master pellet had a diameter of 3 m+++ and a quality of 611 II. This master pellet 100@
Natural pellets (Taflex 410) 5 in f1 part
00 parts by weight were mechanically mixed to prepare a conductive resin composition. 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 contained in Table 1 (Continued) [Effects of the Invention] As is clear from the above explanation and Table 1, the conductive resin composition of the present invention By using a conductive fiber and a low melting point metal together as a conductive filler and blending a flux and a phosphorous antioxidant, the product has good wettability of 81 mm and the conductive fibers have a low melting point. It is strongly bonded by metal, and its conductivity does not decrease even when the environment changes at high temperatures, and its shielding effect has excellent stability over time.

In addition, since the resin has excellent s-electroconductivity, it is possible to reduce the amount of conductive filler to be filled, and furthermore, the unique 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]

FIGS. 1(a) to d) are perspective views showing the conductive filler in the present invention, FIGS. 1(a) to 2) are sectional views of the master pellet in the present invention, and FIG. 2 is a perspective view showing the conductive filler in the present invention. It is a conceptual diagram for explaining the manufacturing process of a master pellet. 1.11... Conductive filler, 2... Conductive fiber,
3...Low melting point metal, 4.14...Thermoplastic resin layer, 10.16...Master pellet.

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 pellet-shaped master pellet integrally coated with (E) a thermoplastic resin layer containing a phosphorous antioxidant, and (F
) A conductive resin composition characterized in that it is blended with thermoplastic resin pellets. 2 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 layer of copper, aluminum or nickel on the surface.Claim 1 The conductive resin composition described in . 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. Claim 1 which is a low humidity solder alloy
The conductive resin composition according to item 1 or 2. 4. The conductive resin composition according to any one of claims 1 to 3, wherein the 4 flux is stearic acid, lactic acid, oleic acid, glutamic acid, or rosin or active rosin. 5 conductive fiber is 0.5 to 3 with respect to the conductive resin composition
The conductive resin composition according to any one of claims 1 to 4, containing 0% by weight. 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. The conductive resin composition according to claim 1, wherein the 8-phosphorus antioxidant is contained in a proportion of 0.1 to 5% by weight based on the thermoplastic resin of the master pellet. 9. The conductive resin composition according to any one of claims 1 to 8, wherein the thermoplastic resin of the master pellet and the resin of the thermoplastic resin pellet are the same. 10. The conductive resin composition according to any one of claims 1 to 9, wherein the thermoplastic resin of the master pellet and the resin of the thermoplastic resin pellet form a blend polymer. 11 (A) conductive fiber, (B) low melting point metal and (C)
A pellet-shaped master pellet formed integrally with (D) a thermoplastic resin layer containing (D) a phosphorus-based antioxidant and (F) a thermoplastic resin pellet is formed on the surface of a conductive filler made of flux. A conductive resin molded article, characterized in that it is made by injection molding a blended conductive resin composition at a concentration higher than the melting point of a low melting point metal.