JP2010189565A - Electroconductive resin composition and electroconductive resin composition molding produced therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a material, as an electroconductive resin composition, containing a metallic powder and a low melting point metal is poor in cost performance and mechanical strengths in the form of a molding and, when injection-molded, suffers from non-electroconductive spots formed on the surface of a molding because of phase separation occurring near the gate due to the viscosity difference between the metallic filler and the matrix resin. <P>SOLUTION: There is provided an electroconductive resin composition which comprises 20-38 vol.% zinc-based metallic powder and a low melting point metal in an amount of 0.1-0.3 time the volume of the zinc-based metallic powder and comprises a glass fiber in an amount 0.09-0.49 time the volume of the matrix resin and can therefore exhibit high cost performance and high mechanical strengths even when the amount of the metallic filler used is small. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a conductive resin composition having high conductivity and high mechanical strength, and a conductive resin composition molded article produced using the conductive resin composition.

In recent years, as a method for imparting high conductivity to a resin, for example, a material having a metal powder and a low-melting point metal as main constituents as described in Japanese Patent No. 3525071 has been reported. The volume resistivity is 5.8 × 10 ^{−5 to} 3.6 × 10 ⁻² Ω · cm, which is high conductivity close to that of a metal material (Patent Document 1).

Patent No. 3525071

In order to obtain high conductivity as described above, the matrix resin must contain a large amount of zinc-based metal powder and a metal filler component which is a low melting point metal, and a molded body in which the space between the metal fillers is narrow and dense is required. there were. Therefore, the density of the molded body was high and the cost performance per volume was low. Further, since the surface of the zinc-based metal powder used is eutectic with tin, which is a low melting point metal, and has good wettability, the low melting point metal is likely to migrate to the surface. For this reason, the low melting point metal and the matrix resin are not easily phase-separated and are well dispersed in the matrix resin. However, during injection molding, a difference in the viscosity between the matrix resin and the metal filler occurs especially near the gate with high shear. Therefore, it is easy to form an imperfect surface of the molded body due to phase separation, and a special molding method is necessary to suppress it, and since the interfacial adhesive force between the metal filler and the matrix resin is low, There was a problem that the mechanical strength was low.

The present invention solves such problems, a conductive resin composition having high mechanical strength of a molded body, excellent cost performance, and hardly causing phase separation between a metal filler component and a matrix resin during injection molding, And providing a method for producing the molded body.

In order to solve the above-mentioned problems, the present inventor uses a metal filler as a composition system in which glass fibers are further added to a composition system in which a zinc-based metal powder and a low melting point metal are used as a metal filler. Even if the glass fiber incorporated in the matrix resin becomes a resistance to physical flow, the minimum necessary conductive network is formed so that the bonding of the metal filler is well spread, And the shape of the glass fiber makes the flow of the molten material uniform, reduces the viscosity difference between the metal filler and the matrix resin at the time of injection molding, and thereby finds the effect of suppressing phase separation, thereby completing the present invention. It is a thing.

Further, the glass fiber has a high aspect ratio and increases the mechanical strength of the molded body. On the other hand, since the glass fiber has a lower density than the metal filler, the density of the molded body is reduced, and a product with excellent cost performance can be provided.

Specifically, as a first invention, there is provided a conductive resin composition comprising a matrix resin containing a zinc-based metal powder, a low melting point metal that melts below the melting point of the matrix resin, and glass fibers.

The second invention is the conductive resin composition as described above, wherein the low melting point metal used is tin or a tin alloy.

As a third invention, the zinc-based metal powder used has an average particle diameter of 1 to 100 μm, and the content thereof is 20 to 38% by volume in the total composition. It is the made conductive resin composition.

According to a fourth aspect of the present invention, the content of the low-melting-point metal used is 0.05 to 0.4 times by volume with respect to the content of the zinc-based metal powder. It is the made conductive resin composition.

As 5th invention, content of the glass fiber used is 0.09 to 0.49 times by volume ratio with respect to content of matrix resin, The electroconductivity described in either of the above characterized by It is an adhesive resin composition.

A sixth invention is the conductive resin composition according to any one of the above, characterized in that the matrix resin used is PPS.

As a seventh invention, the density of a molded product produced using the resin composition is 4 g / cm ³ or less and the volume resistivity is 1.1 × 10 ⁻³ Ω · cm or less. Is a conductive resin composition described in any of the above features.

The eighth invention is the conductive resin composition described in any one of the above, characterized in that the tensile strength of a molded article produced using the resin composition is 35 MPa or more.

According to a ninth aspect of the present invention, there is provided a molded article characterized by being manufactured using any one of the conductive resin compositions described above.

According to the present invention, the conductive resin composition containing the zinc-based metal powder and the low-melting-point metal is blended with glass fiber, so that the content of the zinc-based metal powder is relatively small. High conductivity is obtained. Furthermore, since the density of the obtained molded body can be kept low, a conductive resin composition having high cost performance can be provided. In addition, since this conductive resin composition is unlikely to cause phase separation, a homogeneous electrical contact can be obtained on the surface of the molded body, so that a more reliable conductive molded body can be provided. In addition, since it is possible to provide a molded body having high mechanical strength, the degree of freedom in design becomes higher.

It is the figure which showed the change of the volume resistivity by the compounding quantity of a metal filler. 3 is a SEM photograph of the surface of a molded body of the conductive resin composition of Comparative Example 1. 4 is a SEM photograph of the surface of a molded body of the conductive resin composition of Example 3. 4 is a mapping photograph showing a distribution state of Si elements on the surface of a molded body of the conductive resin composition of Example 3. FIG. It is a mapping photograph which shows the distribution state of Zn element in the molded object surface of the conductive resin composition of Example 3.

The conductive resin composition of the present invention will be described in detail below. The conductive resin composition of the present invention is produced by melt-kneading a zinc-based metal powder, a low melting point metal, a matrix resin, and glass fibers.

Examples of the zinc-based metal powder include metal zinc powder, zinc-iron, zinc-aluminum, zinc-magnesium, brass powder, tin-zinc powder and the like. In particular, metal zinc powder is a low melting point metal, particularly tin and metal zinc. It becomes eutectic on the powder surface and tends to exist as a tin alloy on the metal zinc powder surface. As the form of the metal zinc powder, spherical, elliptical, flaky, teardrop-like powders can be used.

The average particle size of the zinc-based metal powder is preferably 1 to 100 μm, and more preferably about 15 to 80 μm. Note that the smaller the particle size, the more oxide film formed on the particle surface and the worse the conductivity. On the contrary, when the particle size is increased, the dispersibility is lowered and the moldability and the strength of the molded body are lowered.

The low melting point metal may be any conductive metal that can be kneaded in a practical temperature range in the processing of the matrix resin and can be eutectic with the zinc-based metal in the process. For example, if it is PPS, the metal which can be melt-processed at 330 degrees C or less is preferable. As the low melting point metal, bismuth, lead, or an alloy such as tin, tin-zinc, tin-copper, tin-indium, tin-silver, tin-gold can be used. Since the specific gravity is small, it is possible to reduce the density of the molded body as a result, and it is preferable to select tin because the metal is inexpensive. Depending on the intended use, bismuth that has an alloy composition with a high melting point when eutecticized with zinc-based metal powder is also preferred in order to increase the heat resistance of the resulting molded body.
For example, when tin is selected, it forms a eutectic with metallic zinc and has a melting point of around 200 ° C.

In practice, the low melting point metal is blended into the matrix resin as a fine powder. The preferred particle size of the low melting point metal is about 6 to 50 μm in average particle size. The content of the low-melting-point metal is preferably 0.05 to 0.4 times, more preferably about 0.1 to 0.3 times in volume ratio with respect to the content of the zinc-based metal powder. When it is 0.05 times or less, the bonding between the metal particles dispersed in the resin composition is reduced, and the resulting resin composition molded article has poor conductivity. On the other hand, if it is 0.4 times or more, the content of the low-melting point metal tends to be excessive with respect to a state in which a suitable metal-to-metal bond is formed, and the content of the low-melting-point metal is low when kneading or molding the resin composition The melting point metal bleeds out, and the function and appearance of the resulting product are impaired.

Although it does not have a restriction | limiting in particular as a glass fiber, What is necessary is just a shape of the grade which can interrupt | block physically the particle of a eutectic substance in the state contained in the conductive resin composition. Depending on the size of the co-crystal formed, the length and fiber diameter of the required glass fiber vary. For example, the fiber diameter is preferably 1 to 30 μm, and more preferably 5 to 25 μm. Moreover, since fiber length is practical if it is 10-500 micrometers, it is preferable. The aspect ratio is preferably about 5 to 30. If the fiber length of the glass fiber contained in the conductive resin composition obtained after kneading is too long, for example, if it is 500 μm or more, molding becomes difficult, which causes problems in workability and quality. On the other hand, if the fiber length of the glass fiber contained in the conductive resin composition is too short, the eutectic grains of zinc and low-melting-point metal that are adjacent to each other in the matrix resin cannot be blocked. In such a situation, the grains of the eutectic are aggregated, and as a result, the effect of efficiently increasing the conductivity is not exhibited, which is not preferable. Moreover, an effect is not acquired also in the strength improvement of the resin composition molded object obtained. For example, when powdered glass beads are blended, the strength and conductivity of the molded product obtained are much inferior compared to the case where glass fibers are used.

By adding the glass fiber, the glass fiber becomes supplemented with the matrix resin, which has an effect of suppressing the matrix resin from wrapping around so as to wrap around the metal filler, and the conductive resin is maintained in the matrix resin. This is preferable because it is efficiently dispersed.

In actual production, glass fiber is cut during kneading, so that the glass fiber length used as a raw material should be longer. In this regard, it is necessary to select appropriately according to the equipment and conditions used in the kneading step. For example, when a raw material containing glass fibers is preliminarily mixed and then kneaded with a biaxial kneader, the fiber length is preferably about 1 to 6 mm. If the length is longer than this, a problem occurs in that the torque becomes high in the kneading step and the dispersion cannot be sufficiently performed.

The glass fiber content is preferably 0.09 times or more by volume with respect to the matrix resin content. When the content is less than this, the effect of the present invention, which remarkably increases the conductivity of the obtained conductive resin composition, is not obtained, and the effect of increasing the strength of the molded article is not significant. When the content is too high, the workability tends to decrease, and 0.7 times or less is preferable. Considering processing by injection molding, 0.49 or less is preferable. If it is 0.09 times or less, the effect of increasing the strength of the molded article is thin, and the matrix resin inhibits the formation of a conductive network, resulting in poor conductivity.

The zinc-based metal powder and glass fiber may be previously treated with a coupling agent such as silane, titanate, or aluminate, oil, or the like on the surface thereof.

The matrix resin may be a thermoplastic resin or a thermosetting resin, and can be plastically processed at a melting point higher than that of the low melting point metal used. Any eutectic crystal of the melting point metal and the zinc-based metal may be used. Examples of the thermoplastic resin include polyolefin resins, polyester resins, polycarbonate resins, polystyrene resins, acrylic resins, polyamide resins, polyphenylene ether resins, polyphenylene sulfide resins, and polyether resins. Examples include terketone resins, polysulfone resins, fluorine resins, various elastomers modified from the above resins, and alloy resins. These thermoplastic resins are used in at least one kind, and can be used in combination of two or more kinds. Further, the selection of the resin requires careful selection in consideration of the melting point of the resin and the melting point of the low melting point metal used.

Examples of the thermosetting resin include phenol resin, furfural resin, epoxy resin, urea resin, melamine resin, vinyl ester resin, unsaturated polyester resin, polyurethane resin, thermosetting acrylic resin, diallyl phthalate. Examples thereof include a resin, a silicone resin, and an amino resin. These thermosetting resins are used in at least one kind, and can be used in combination of two or more kinds without any particular limitation. Moreover, it can also combine in the kind of hardening | curing agent, hardening accelerator, etc. which are used for these.

Furthermore, the conductive resin composition of the present invention is composed of one or two kinds of plasticizer, external mold release agent, internal mold release agent, thermal stabilizer, antioxidant, sliding agent, stabilizer, flame retardant and the like. You may mix | blend the above in combination.

The conductive resin composition of the present invention can be produced by utilizing a conventional method and processing equipment for processing thermoplastic resins, thermosetting resins, rubbers and the like. That is, in the step of premixing and dispersing zinc-based metal powder, low melting point metal, and glass fiber filler and matrix resin, a tumbler mixer, a Henschel mixer, a super mixer, a high speed mixer, Preliminarily mix and disperse using a mixing device such as a Leedige mixer. This is melt kneaded using a single-screw or twin-screw extruder, a Banbury mixer, a kneader or the like, and extruded to obtain a conductive resin composition for molding. In addition, in glass fiber, you may add with a side feed in the middle of melt-kneading. The shape of the molding compound obtained here is not particularly limited, and may be in the form of a lump, granule, or powder, and may be processed into a shape suitable for molding later if necessary. good.

The method for molding the conductive resin composition of the present invention can be produced using a conventional method for general synthetic resins such as injection molding, hot press molding, transfer molding and roll molding. In the injection molding, a molded body can be obtained by using a general injection molding machine and a predetermined mold. More preferably, a more homogeneous molded body can be obtained by using injection compression molding or injection press molding. The injection compression molding and injection press molding referred to here is a method of injecting molten material into a mold with a gap slightly larger than a predetermined speed at a high speed, and when the injection is completed and the material is filled, the mold reaches a predetermined position. It is a method with a mechanism that closes while applying pressure. Use of this molding method is preferable because the molten material is uniformly pressurized in the mold and the metal filler and the matrix resin are unlikely to undergo phase separation.

Moreover, the conductive resin composition of the present invention can form an electric circuit by two-color molding. That is, the conductive resin composition of the present invention is secondarily molded on a molded body having a circuit groove formed of a nonconductive resin composition, or nonconductive with respect to the conductive resin composition previously molded into a circuit shape. An excellent resin-molded electric circuit component can be obtained by outsert-molding the conductive resin composition.

The present invention will be described in detail based on examples and comparative examples as follows, but the present invention is not limited to these examples.

(Kneading and molding) Examples 1 to 8 and Comparative Examples 1 to 4 used PPS as the matrix resin, and used zinc metal powder and tin (melting point 232 ° C.) as the low melting point metal. Further, in Comparative Examples 5 to 9, various fillers were blended in the volume ratios shown in the table instead of the glass fibers used in Example 3. These were dry-mixed for 3 minutes with a mixer and melt-kneaded and extruded using a twin-screw kneader set at 300 ° C. The obtained compound was molded at 315 ° C. by general injection molding to produce a molded body (length 127.0 mm, width 13.0 mm, thickness 3.0 mm). The injection moldability at that time is (x) when the phase separation appears in the vicinity of the molded body gate or on the surface, and (◯) when the phase separation does not appear.

(Evaluation of strength) Tensile strength was measured using the obtained molded product. The head speed was 5 mm / second.

(Measurement of volume resistivity) Kneading with a batch type small kneader set at 330 ° C for 3 minutes, taking out the kneaded material, crushing it after cooling, and plate with a hot press set at 330 ° C (80 mm square, thickness 3.0 mm) was molded and its volume resistivity was measured. Here, the volume resistivity was measured using a four-probe method based on JIS K7194. The lower the volume resistance value, the higher the conductivity.

(Evaluation of kneadability) Evaluation of kneadability of conductive resin plastics is judged by the kneading torque value when kneading with a batch type small kneader, and if this value becomes high, the fluidity of the material tends to be poor And practicality is reduced. A value suitable for injection moldability is preferably less than 1.5 kg · m. The kneading dispersibility was evaluated by repelling and separating the melted low melting point metal from the kneaded material in which the melted low melting point metal was integrated in the small batch type kneader. The case where it was pulled out (×), and the case where the low melting point metal was not separated and was dispersed in the resin plastic material was indicated as (◯).

(SEM observation, element mapping) SEM observation is performed on the surface of the molded body using the obtained conductive resin composition, and in order to investigate the distribution state of the contained component, the content of the contained component is measured by an energy dispersive X-ray analyzer. Elemental mapping was performed.

Example 1 Zinc metal powder (30 μm; 20% by volume), tin powder (45 μm under; 4.0% by volume), glass fiber (chopped; 20% by volume) were mixed in PPS resin, and melt-kneaded. A compound of about 3 to 5 mm was produced by extrusion and cutting. This compound was injection molded to obtain a plate-shaped injection molded body having a length of 127.0 mm, a width of 13.0 mm, and a thickness of 3.0 mm. There was no phase separation in the vicinity of the gate of this injection molded body. Further, when the same composition was kneaded with a batch type small kneader, the dispersion was good without particularly separating the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The tensile strength of the obtained injection-molded product was as high as 78 MPa, and the volume resistivity of the injection-molded product and the press-molded product was measured. Value; 1.1 × 10 ⁻³ Ω · cm).
Example 2 Zinc metal powder (30 μm; 25% by volume), tin powder (45 μm under; 4.0% by volume), glass fiber (chopped; 15% by volume) were mixed in PPS resin, and melt-kneaded. A compound of about 3 to 5 mm was produced by extrusion and cutting. This compound was injection molded to obtain a plate-shaped injection molded body having a length of 127.0 mm, a width of 13.0 mm, and a thickness of 3.0 mm. There was no phase separation in the vicinity of the gate of this injection molded body. Further, when the same composition was kneaded with a batch type small kneader, the dispersion was good without particularly separating the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The tensile strength of the obtained injection-molded product was as high as 69 MPa, and the volume resistivity of the injection-molded product and the press-molded product was measured. Value; 3.7 × 10 ⁻⁴ Ω · cm).
(Example 3) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 15% by volume) were mixed in PPS resin, and melt-kneaded. A compound of about 3 to 5 mm was produced by extrusion and cutting. This compound was injection molded to obtain a plate-shaped injection molded body having a length of 127.0 mm, a width of 13.0 mm, and a thickness of 3.0 mm. There was no phase separation in the vicinity of the gate of this injection molded body. Further, when the same composition was kneaded with a batch type small kneader, the dispersion was good without particularly separating the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The tensile strength of the obtained injection-molded product was as high as 61 MPa, and the volume resistivity of the injection-molded product and the press-molded product was measured. Value; 8.3 × 10 ⁻⁵ Ω · cm).
(Example 4) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 5% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was higher than that of Example 3 (5.7 × 10 ⁻⁴ Ω · cm).
(Example 5) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 10% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was slightly higher than that of Example 3 (1.3 × 10 ⁻⁴ Ω · cm).
(Example 6) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 20% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was comparable to that of Example 3 (9.5 × 10 ⁻⁵ Ω · cm).
(Example 7) Zinc metal powder (30 μm; 30% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 10% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. Although the volume resistivity of the obtained press-molded body was set to a higher density than Example 2 (3.7 × 10 ⁻³ Ω · cm), it was high, the glass fiber amount was low, and the same PPS amount was further blended. In this case, it can be seen that the formation of the conductive network is bad.
(Example 8) Zinc metal powder (30 μm; 15% by volume), tin powder (45 μm underer; 3.0% by volume), glass fiber (chopped; 15% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The volume resistivity of the obtained press-molded body is (1.7 × 10 ⁴ Ω · cm) and the zinc metal powder is rapidly increased when it is less than 20% by volume.
Comparative Example 1 Zinc metal powder (30 μm; 50% by volume) and tin powder (45 μm under; 6.5% by volume) were mixed in PPS resin, melt kneaded, extruded, and cut to a compound of about 3 to 5 mm. Was made. This compound was injection molded to obtain a plate-shaped injection molded body having a length of 127.0 mm, a width of 13.0 mm, and a thickness of 3.0 mm. Phase separation was observed in the vicinity of the gate of this injection molded body. Further, when the same composition was kneaded by a batch type small kneader, the tin alloy was not particularly separated and the dispersion was good. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The tensile strength of the obtained injection-molded product is as low as 25 MPa. When the volume resistivity of the obtained injection-molded product and the press-molded product was measured, both had the same low volume resistivity (5.6 × 10 ⁻⁵ Ω · cm).
(Comparative Example 2) When zinc metal powder (30 μm; 45% by volume) and tin powder (45 μm under; 6.5% by volume) were mixed in PPS resin and kneaded by a batch type small kneader, Dispersion was good without separation of low melting point metals, and kneading torque was as low as 0.5 kg · m. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. The volume resistivity of the obtained press-molded product was (8.5 × 10 ⁻⁵ Ω · cm), and increased slightly due to the weight loss of the zinc metal powder.
(Comparative Example 3) When zinc metal powder (30 μm; 35% by volume) and tin powder (45 μm underer; 4.5% by volume) were mixed in PPS resin and kneaded by a batch type small kneader, Dispersion was good without separation of low melting point metals. The kneading torque was as low as 0.1 kg · m and almost liquid. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, a high volume resistivity was obtained (8.6 × 10 ⁻² Ω · cm).
(Comparative Example 4) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), glass fiber (chopped; 25% by volume) were mixed in PPS resin and batch-type compact When kneaded with a kneader, the dispersion was good without any separation of the low melting point metal. The kneading torque was as high as 20 kg · m. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was slightly higher than that of Example 3 (1.4 × 10 ⁻⁴ Ω · cm).
(Comparative Example 5) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 4.5% by volume), carbon fiber (chopped; 15% by volume) were mixed in a PPS resin and batch-type compact When kneading with a kneader, the dispersion was good with no separation of the low melting point metal, but the kneading torque was a little as high as 1.6 kg · m. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was higher than that of Example 3 (1.7 × 10 ⁻⁴ Ω · cm). Although it was predicted that the carbon fiber contributes to the formation of the conductive path, contrary to the prediction, the volume resistivity was larger than that of the glass filler. Since the eutectic was separated, it was considered that the conductive path could not be formed efficiently because the eutectic was fixed on the carbon fiber surface.
(Comparative Example 6) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 45% by volume), artificial graphite (100 μm in bowl shape; 15% by volume) are mixed in PPS resin and batch-type compact When kneading with a kneader, the dispersion was good without any separation of the low melting point metal, and the kneading torque was as low as 0.4 kg · m. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press-formed body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was higher than that of Example 3 as in Comparative Example 1 (15 × 10 ⁻⁴ Ω · cm). This was presumed that the eutectic was fixed in the vicinity of the surface of carbon-based graphite as in Comparative Example 5.
(Comparative Example 7) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 45% by volume), silicon (Si) powder (spherical 70 μm; 15% by volume) were mixed in a PPS resin and batch type When the mixture was kneaded with a small kneader, the low-melting point metal was not particularly separated and the dispersion was good. The kneading torque was as low as 0.1 kg · m and almost liquid. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press molded body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was higher than that of Comparative Example 5 (6.6 × 10 ⁻⁴ Ω · cm). Spherical silicon powder is taken into the matrix resin but has a low viscosity and behaves like a matrix resin, and since the aspect ratio is small, the effect of inhibiting the eutectic from aggregating is not as high as glass fiber. It was thought that the effect as seen with glass fiber was not observed.
(Comparative Example 8) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm under; 45% by volume), ferrite powder (hexagonal plate 4 μm; 15% by volume) were mixed in a PPS resin and batch type When kneaded with a small kneader, separation of the low melting point metal was observed. The kneading torque was as low as 0.1 kg · m and almost liquid. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press molded body. When the volume resistivity of the obtained press-molded product was measured, it was higher than that of Comparative Example 3 (1.1 × 10 ⁻³ Ω · cm). It was considered that the oxide filler could repel the low melting point metal in the material and could not successfully form a conductive network.
(Comparative Example 9) Zinc metal powder (30 μm; 35% by volume), tin powder (45 μm underer; 45% by volume), and talc (13 μm; 15% by volume) were mixed in a PPS resin and batch type compact kneader When kneaded at −, separation of the low melting point metal was observed. The kneading torque was as low as 0.3 kg · m and was almost liquid. This was taken out and pulverized, and then pressed into a plate having an 80 mm square and a thickness of 3.0 mm to obtain a press molded body. When the volume resistivity of the obtained press-molded product was measured, the volume resistivity was higher than that of Comparative Example 3 as in Comparative Example 4 (15 × 10 ⁻³ Ω · cm). It has been considered that talc also repels low melting point metals in the material like the oxide filler and cannot form a conductive network.

Here, Table 1 shows the contents of metal zinc powder (Zn), metal tin (Sn), which is a low melting point metal, and glass fiber and PPS which is a matrix resin, and the evaluation results thereof used in Examples and Comparative Examples. Summarized.

Moreover, FIG. 1 summarizes the relationship between the eutectic content (Zn + Sn) and the volume resistivity of the conductive composition molded body forming these numerical values. When glass fiber is not included (in the figure, “without GF” Comparative Example 1, Comparative Example 2, Comparative Example 3), when glass fiber is included (in the figure, “with GF” Examples 1 to In Example 3 and Comparative Example 9), it can be seen that the volume resistivity is low even at the same content, and the eutectic content required to achieve the same volume low efficiency is low.

Here, the glass fiber blended in the blending of Example 3 was compared and evaluated in Table 2 by comparing and evaluating the difference in effect when the glass fiber was replaced with fillers having different compositions and shapes.

It can be seen that when glass fibers are used (Example 3), the conductivity is higher than when other fillers are used (Comparative Examples 5 to 9).

The conductive resin composition in a suitable range had a tensile strength of 35 MPa or more. Moreover, the density of the obtained molded product was 4.0 g / cm ³ or less, and the volume resistivity was 1.1 × 10 ⁻³ Ω · cm or less.

FIG. 2 is an SEM photograph of the surface of the molded body of the conductive resin composition when no glass fiber is contained (Comparative Example 1). 1 shows a eutectic of zinc and tin, which is a lump of about 10 to 100 μm, which are connected to each other to form a larger lump with a neck. Shown in 2 is PPS which is a matrix resin.

On the other hand, FIG. 3 is a SEM photograph of the surface of the molded body of the conductive resin composition of Example 3 of the present invention, which is a case where glass fibers are included. 1 is a eutectic of zinc and tin, 2 is PPS which is a matrix resin, and 3 is a glass fiber. 4 and 5 are the main components of silicon (Si), which are the main components of the glass fiber, and the eutectic, for the same portion of the surface of the molded product of the resin composition molded product shown in FIG. The distribution state of zinc (Zn) is mapped. Since the part where the element is detected is represented by a white dot (signal), the part where the element exists is shown in white.
In the case of Comparative Example 1 shown in FIG. 2, that is, in the case where no glass fiber is contained, in Example 3 shown in FIG. 3, the eutectic of zinc and tin shown in FIG. It turns out that it becomes a lump of about 10-100 micrometers, and they are mutually connected and become a larger lump with a neck, and form a conductive network. On the other hand, in FIG. 4, it can be seen that the Si lumps indicated by 4 in the figure are rod-shaped and arranged in a substantially horizontal direction. Moreover, in FIG. 5, it can be seen that the lumps indicating the presence of Zn shown in FIG. 3 to 5, it can be seen that the glass fibers are oriented substantially in the horizontal direction, and the eutectics are also arranged substantially horizontally in a state of being interrupted by them. It can be seen that the glass fibers are neatly dispersed in the matrix resin and the eutectic is dispersed while efficiently securing a bonded state therebetween, thereby forming a conductive network.

The present invention can be applied to materials used in the field of transferring heat, such as heat conduction and cooling, in addition to fields that use electrical resistance such as energization, electrostatics, ESD countermeasures, resistors, and heat generation.

1 Eutectic of metallic zinc and metallic tin 2 PPS
3 Glass fiber 4 Signal indicating Si element 5 Signal indicating presence of Zn element

Claims (9)

A conductive resin composition comprising a matrix resin comprising a zinc-based metal powder and a low melting point metal that melts at or below the melting point of the matrix resin, and glass fibers. The conductive resin composition according to claim 1 or 2, wherein the low melting point metal used is tin or a tin alloy. The average particle size of the zinc-based metal powder used is 1 to 100 µm, and the content thereof is 20 to 38% by volume in the total composition. Conductive resin composition. The content of the low melting point metal used is 0.1 to 0.3 times in volume ratio with respect to the content of the zinc-based metal powder. Conductive resin composition. The electrical conductivity according to any one of claims 1 to 4, wherein the content of the glass fiber used is 0.09 to 0.49 times by volume with respect to the content of the matrix resin. Resin composition. The conductive resin composition according to claim 1, wherein the matrix resin used is PPS. The density of a molded article produced using the resin composition is 4 g / cm ³ or less and the volume resistivity is 1.1 × 10 ⁻³ Ω · cm or less. The conductive resin composition according to claim 2. 3. The conductive resin composition according to claim 1, wherein a tensile strength of a molded body produced using the resin composition is 35 to 85 MPa. A conductive resin composition molded article characterized by being manufactured using the conductive resin composition according to claim 1.