JPS63238162A - Electrically conductive resin composition and molded article thereof - Google Patents

Abstract

PURPOSE:To obtain the titled composition capable of keeping excellent electrical conductivity even at a high temperature, having excellent age stability and moldability and suitable for electronic apparatuses, etc., by coating a surface of an electrically conductive fiber with a thermoplastic resin containing a low- melting metal and a phosphorus-based antioxidant. CONSTITUTION:(A) Electrically conductive fiber (e.g. copper fiber or brass fiber) having a diameter of 5-100mum is surface-coated and integrated with (B) a thermoplastic resin (e.g. general polypropylene) containing (B1) a low- melting metal (e.g. general soldering alloy composed mainly of Sn or Sn-Pb) and (B2) a phosphorus-based antioxidant and the product is pelletized. The amount of the component A is 0.5-80wt.% based on the whole composition and the amounts of the component B1 and the component B2 are 5-30wt.% based on the component A and 0.1-5wt.% based on the thermoplastic resin, respectively.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention provides a highly reliable conductive resin composition with excellent conductivity, particularly its stability over time at high temperatures, and molded products thereof. Regarding.

(Prior Art) Conventionally, conductive resin compositions have been prepared by blending conductive materials with thermoplastic resins, and these compositions have been used in conductive resin molded articles. In many cases, carbon-based conductive fibers have been blended into these materials, but their purpose is to prevent static electricity.
It has low conductivity and is not very effective for electromagnetic shielding, which has become a problem in recent years. Therefore, attempts have been made to improve conductivity by using metal-based conductive fibers for electromagnetic shielding.

However, when metal-based conductive fibers (hereinafter referred to as metal fibers) are blended, the specific gravity increases, which significantly impairs the original properties of the resin, so it is necessary to minimize the amount blended. .

However, when the blending amount of metal fibers is reduced, the conductivity decreases, and furthermore, the usage environment is severely restricted. That is, since there is a difference in thermal expansion between the resin and the metal fibers used, a problem arises in that conductivity deteriorates at high temperatures.

Therefore, at present, it is put into practical use by increasing the amount of gold and miscellaneous components M in order to prevent the decrease and deterioration of the conductivity, and to limit the environment in which it is used. As such, conventional conductive resin compositions of metal fibers and molded products thereof have problems in that they have limitations in their applications and usage environments, and have unstable characteristics and low reliability.

Also, it is known that conductivity can be obtained by mixing and molding a low melting point metal and a resin, but the low melting point metal has poor adhesion with the resin and separates, reducing the physical properties of the resin. In addition, when changing the color of the material in the molding machine, there was a problem in that it was extremely dangerous in terms of the molding process, such as blank punching and metal scattering. Furthermore, when gold 1/1m fibers are used in combination with low-melting point metals and mixed into resin, an oxide film is formed on the surface of the metal fibers due to drying before molding, resulting in poor solderability and separation of the low-melting point metals. There was a problem in that the metal fibers were corroded and the conductivity deteriorated significantly as a result.

(Problems to be Solved by the Invention) The present invention was made to solve the above problems, and the conductive fibers have good wettability and the low melting point metal is firmly bonded to the conductive fibers. , the conductivity of the molded product does not deteriorate even at high temperatures and has excellent stability over time, and there is no separation or scattering of the resin and low-melting point metal during molding, resulting in good moldability and highly reliable conductivity. The present invention aims to provide a resin composition and a molded article thereof.

[Structure of the Invention] (Means for Solving the Problems) As a result of intensive research aimed at achieving the above object, the present inventors have developed a method using conductive fibers, low melting point metals, and phosphorous antioxidants. By using a composition consisting of a blended thermoplastic resin, the conductivity of the molded product does not deteriorate even at high temperatures and has excellent stability over time, and the separation and scattering of the resin and low-melting metal during molding can be avoided. The present invention was completed based on the discovery that it is possible to obtain a highly reliable conductive resin composition and a molded article thereof, which has improved molding processability. That is, the present invention provides (A) on the surface of the conductive fiber, (B) a low melting point metal and (
C) A conductive resin composition comprising (D) a thermoplastic resin containing a phosphorous antioxidant, which is formed into a single piece and cut into pellets.

Further, the present invention is a conductive resin molded article characterized by being formed by injection molding this conductive resin composition at a temperature equal to or higher than the melting point of a low-melting point metal.

The conductive fibers (A) used in the present invention include metal fibers such as long-fiber copper fibers, stainless steel fibers, brass fibers, aluminum fibers, and nickel fibers, and metal fibers having a metal layer of copper, aluminum, nickel, etc. on the surface. Examples include organic II cloth and inorganic fibers, which may be used alone or in combination of two or more. The diameter of the conductive fibers is preferably about 5 to 100 μI.

The conductive fibers are coated with a thermoplastic resin containing a low melting point metal and a phosphorous antioxidant on the surface thereof, and then cut into 5 to 8 fibers in length to obtain a resin composition. The amount of conductive fibers to be blended is desirably 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 low melting point metal (B) used in the present invention is a general solder alloy containing 3n or Sn-Pb as a main component, Sn-
Examples include high-temperature solder alloys containing Pb-Cd-A (1-Zn as the main component) and low-temperature solder alloys containing Sn-Pb-Cd-Bi as the main component. It may be granular, linear, or flaky, and is not particularly limited in shape.
The low melting point metal is preferably selected depending on the molding temperature of the thermoplastic resin to be mixed. It is more preferable to select and use a low melting point metal that has a melting point that melts at the highest temperature part of the heating cylinder of the injection molding machine. The blending ratio of the low melting point metal is preferably an amount sufficient to bond and coat the conductive fibers, and is preferably blended at a ratio of 5 to 30% by weight based on the conductivity mm. If the amount 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 undesirable. It is preferable that the low melting point metal is blended into the thermoplastic resin.

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

(Sanko Kagaku Co., Ltd., product name) MARK PEP24 MARK PEP36 MARK 329K MARK 1178 R=C, alkyl group of 2 to CI5 (more than 7 deg. Argus Co., Ltd., product name) MARK
The blending ratio of the 1500 phosphorus antioxidant is preferably 0.1 to 5% by weight based on the thermoplastic resin. If the blending amount is less than 0.1%, it is insufficient to remove the oxide film from the conductive fibers, poor solder wettability, and
If it exceeds % 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 thermoplastic resin.

The thermoplastic resin (D) used in the present invention includes polypropylene resin, polyethylene resin, polystyrene resin, acrylonitrile-butadiene-styrene resin, modified polyphenylene oxide resin, polybutylene terephthalate resin, polycarbonate resin, polyamide resin, polyetherimide resin, etc. These can be used alone or in combination.
Use by mixing more than one species. It is desirable that the above-mentioned low melting point metal and phosphorous antioxidant be blended into this thermoplastic resin, so that the conductive materials are integrated into the coating.

These may be those in which the third synthetic resin formed at the interface by mixing thermoplastic resins has a reinforcing effect, that is, a blended polymer.

For example, when using a modified polyphenylene oxide resin, polycarbonate resin, etc. as the thermoplastic resin, good results can be obtained if a styrene-based thermoplastic resin is used as the other thermoplastic resin.

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

The conductive resin composition of the present invention and molded articles thereof are manufactured by conventional methods. The fibrous conductive fibers are passed through the die of an extruder and subjected to l1m conductive fibers. A thermoplastic resin containing a low melting point metal and a phosphorous antioxidant is coated and integrated on the surface of the material, and then cut into an appropriate size to obtain a pellet-shaped conductive resin composition. This composition usually has a circular cross section, but the cross section is not limited to a particular shape and may be flat or other shapes. Although it is economically advantageous to carry out the manufacturing process of this composition continuously, it does not necessarily have to be continuous and may be manufactured in a batch manner. The type of thermoplastic resin and the possibility thereof are appropriately selected depending on the characteristics required of the conductive resin composition and its molded product. The conductive resin composition thus produced is injection molded at a temperature equal to or higher than the melting point of the low melting point metal to obtain a conductive resin molded article. The molded product can be used as housings or parts for electronic equipment, measuring equipment, communication equipment, etc. that require electromagnetic shielding.

(Function) According to the present invention, excellent effects can be obtained by using conductivity 111 ft, a low melting point metal, a phosphorous antioxidant, and a thermoplastic resin.

That is, the conductive resin composition is formed during the manufacturing process or during drying when the thermoplastic resin and the conductive m-fiber are kneaded in the heating cylinder of the injection molding machine. The IN oxide film is removed by the reducing action of a phosphorous antioxidant. Next, the surface of the conductive fibers is firmly coated with a low melting point metal melted in a high temperature section within the cylinder. In this case, if an oxide film remains on the conductive fibers or the solder wettability is poor, the conductive fibers will corrode or the low melting point metal will be liberated, deteriorating the physical properties of the resin. Then, when the conductive resin composition is injected into the mold and cooled and solidified, the bonding points between the conductive fibers are fused by the low melting point metal to form a network, which is then cooled and solidified. Therefore, even if the molded product is placed in a high-temperature environment, the bonding points between the conductive fibers will not separate, and the conductivity will not deteriorate.

This can be confirmed by dissolving the resin component of the molded article with a solvent and confirming the state of the network in which the conductive fibers are bonded.

Therefore conductivity a! It becomes possible to reduce the miscellaneous mixture ω. Furthermore, depending on the molding temperature of the thermoplastic resin, it is possible to select a low melting point metal that melts at the highest temperature portion of the heating cylinder of the injection molding machine, thereby eliminating separation and scattering of the low melting point metal.

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

Example 300 converged copper fibers with a diameter of 50 μm, low melting point metal beads (3N40%, Pb60%) and HCA (
Toughflex 410 (ABS resin, trade name, manufactured by Mitsubishi Monsanto) containing a phosphorus antioxidant (trade name, manufactured by Sangen Kagaku Co., Ltd.) was passed through a die of an extruder to form an ABS resin melt coating on the surface of the copper fiber.

This was cooled and cut into lengths of 6 fibers in the Il miscellaneous force direction using a pelletizer to produce a conductive resin composition.

The copper fiber filling rate of this composition was 60% by weight.

Injection molding was performed using this conductive resin composition to obtain a molded article. The obtained molded product was tested for volume resistivity and shielding effect, and the results are shown in Table 1, and the extremely remarkable effects of the present invention were confirmed.

Comparative Example In the example, a conductive resin composition and a molded article were made in the same manner as in the example except for the phosphorus antioxidant, and the molded article was tested in the same manner as in the example. The results are shown in Table 1.

Table 1 "Effects of the Invention" As is clear from the above explanation and Table 1, the conductive resin composition of the present invention uses conductive VA fibers, a low melting point metal, and a phosphorous antioxidant. As a result, the wettability of the conductive I! miscellaneous material is good and the bond between the conductive I! fibers becomes strong.
As a result, it has excellent conductivity, making it possible to reduce the amount of conductive fiber blended, and also improves molding processability because there is no separation or scattering of the thermoplastic resin and low-melting metal during molding. .

A molded article using this conductive resin composition has excellent electromagnetic shielding effect over time without a decrease in conductivity even under environmental changes at high temperatures. If this molded product is used in electronic equipment, communication equipment, etc., extremely high reliability can be provided.

Procedural amendment (voluntary) December 4, 1985 1. Indication of the case 1988 Patent Application No. 71568 2. Title of the invention Conductive resin composition and its molded product 3. Relationship with the person making the amendment Patent applicant 6: Number of inventions increased by amendment 0 Simple explanation column 1 and "Drawing j" 8. Contents of amendment (1) Scope of claims As attached (2) Page 7, line 5 of the specification , delete r-Cd J.

(3) Page 7, lines 6-7 of the specification, r-cd, is deleted.

<・4) On page 7, lines 12 to 15 of the specification, ``It is more preferable to select and use a low melting point metal that has a melting point that melts at the highest temperature part of the heating cylinder of the injection molding machine. .” is deleted.

(5) On page 13, line 20 of the specification, Delete "high temperature part of".

(6) From lines 14 to 17 on page 14 of the specification, the phrase "because the thermoplastic resin... can be selected" is deleted.

(7) In the first line of page 16 of the specification, "shown" was replaced with "shown." Also, the molded product was washed with methylene chloride, the resin content was dissolved, and the network state of the remaining conductive fibers was examined electronically. I took a photo with the HR bell, and it is shown in Figure 1. It can be seen that the conductive fiber 1 and the conductive fiber 2 are firmly fused and bonded by the low melting point metal 3." .

(8) Next to page 17, line 14 of the specification:

[Brief explanation of drawings]

FIG. 1 is an electronic and mirror photograph showing the shape of the conductive fibers fused and bonded in a network shape with a low melting point metal in the molded article of the present invention. 1.2...Conductive fiber, 3...Low melting point metal, J is added. (9) Claim 1 characterized by Figure 1 of the attached drawing (A) The surface of the conductive fiber contains (B) a low melting point metal and <C> a phosphorus-based antioxidant (D) thermoplastic 1. A conductive resin composition comprising a resin formed by integrally forming a coating and cutting the resin into pellets. 2. A patent in which the conductive g+ fibers are copper fibers, yellow fibers, stainless fibers, aluminum fibers, nickel fibers 1; The conductive resin composition according to claim 1. 3. The conductive resin composition according to claim 1 or 2, wherein the low melting point metal is a solder alloy containing Sn or Sn-Pb as a main component. 4. Claims 1 to 3, wherein the conductive fiber is contained in a proportion of 0.5 to % by weight based on the entire composition.
2. The conductive resin composition according to any one of Items 1-1. 5 5 to 30% by weight of low melting point metal based on the conductive fiber
The conductive resin composition according to any one of claims 1 to 4, which is blended in a proportion of . 6 Add phosphorus antioxidant to thermoplastic resin at a rate of 0.1
The conductive resin composition according to any one of claims 1 to 5, which is blended in a proportion of ~5% by weight. 7. A conductive resin composition in which (A) a conductive fiber is coated with (B) a low melting point metal and (C) a (D) thermoplastic resin containing a phosphorous antioxidant, which is integrally formed on the surface and cut into pellets. A conductive resin molded product, characterized by being injection molded at a temperature higher than the melting point of a low melting point metal. Figure 1 Procedural amendment (voluntary) March 16, 1988 2. Title of the invention: Conductive resin composition and its molded product 3. Relationship with the case of the person making the amendment: Representative of the patent applicant: Hideo Osawa ( 6. Number of inventions increased by amendment 07. Subject of amendment ``Detailed description of the invention column'' and ``Drawings'' of the specification 8. Contents of amendment (1) Page 7 of the specification Delete r-ZnJ in line 5. (2) Figure 1 of the drawings shall be amended as shown in the attached sheet. Figure 1

Claims (1)

[Scope of Claims] 1 (A) A thermoplastic resin containing (B) a low melting point metal and (C) a phosphorous antioxidant is applied to the surface of the conductive fiber,
A conductive resin composition characterized in that it is formed by integrally forming a coating and cutting it into pellets. 2. Conductive fibers include copper fibers, brass fibers, stainless steel fibers,
The conductive resin composition according to claim 1, which is an aluminum fiber, a nickel fiber, an organic fiber having a layer of copper, aluminum or nickel on the surface, or an inorganic fiber. 3 The low melting point metal is a general 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 Sn-Pb-Cd-B.
The conductive resin composition according to claim 1 or 2, which is a low-temperature solder alloy containing i as a main component. Claims 1 to 3 in which the conductive fibers are contained in a proportion of 0.5 to 80% by weight based on the entire composition.
2. The conductive resin composition according to any one of Items 1-1. 5. The conductive resin composition according to claim 1, wherein the low melting point metal is blended in a proportion of 5 to 30% by weight based on the conductive fibers. Add 6-phosphorus antioxidant to thermoplastic resin from 0.1 to
The conductive resin composition according to any one of claims 1 to 5, which is blended in a proportion of 5% by weight. 7 (A) A thermoplastic resin containing (B) a low melting point metal and (C) a phosphorous antioxidant is applied to the surface of the conductive fiber,
1. A conductive resin molded article, characterized in that it is made by injection molding a conductive resin composition that has been integrated with a coating and cut into pellets at a temperature higher than the melting point of a low melting point metal.