Conductive thermoplastic resin composition and method for producing the same

Abstract

To provide a conductive thermoplastic resin composition and a method for producing the same, capable of yielding a molded article that excels in conductivity and its consistency, and visual quality.SOLUTION: A conductive thermoplastic resin composition comprises 50 to 70 mass% of a thermoplastic resin (A), 28 to 42 mass% of aluminum fine particles (B), and 0 to 10 mass% of carbon black (C), based on 100 mass% of the thermoplastic resin composition, wherein the total amount of the aluminum fine particles (B) and the carbon black (C) is 38 to 42 mass% based on 100 mass% of the thermoplastic resin composition, and the aluminum fine particles (B) have an average particle diameter of 250 μm or less as measured by a sieving method.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive thermoplastic resin composition excellent in conductivity and appearance of the obtained molded article and a method for producing the same.

Background Art

[0002] There is known a resin molded body in which a metal such as aluminum is used in the form of metal particles, metal short fibers, metal foil, etc. and contained in a resin. For example, in Patent Document 1, a resin composition containing flaky (lamellar) aluminum having an average particle diameter of 3 to 100 μm, an average thickness of 0.1 to 10 μm, and an aspect ratio of 5 to 100 with respect to a propylene-based resin and a molded body using the same are disclosed to be excellent in water vapor permeability.

[0003] Further, in Patent Document 2, it is disclosed that a resin molded product obtained by adding small pieces of aluminum foil having a square shape and having a specific thickness and size to a thermoplastic resin at a ratio of 0.1 to 10% has high designability and design. In Patent Document 3, it is disclosed that a resin molded body containing fine pieces of a laminate of a metal foil and a plastic film, in which the fine pieces of the foil-shaped metal are randomly adhered to each other or randomly dispersed in another substrate, is excellent in electromagnetic shielding properties.

[0004] Furthermore, in Patent Document 4, there is disclosed a conductive resin molded body containing a thermoplastic resin and foil-shaped metal pieces having an average area of the main surface of 0.3 to 50.0 mm 2 and having a content ratio of the foil-shaped metal pieces in the molded body of 10.0 to 60.0% by mass, which is excellent in mechanical strength and conductivity.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, the resin compositions and molded articles disclosed in Patent Documents 1 to 3 are not intended for use in applications where conductivity is required and do not have sufficient conductivity. Although the molded article of Patent Document 4 has a certain conductivity, there is a demand for a molded article having further conductivity. In addition, since the molded articles disclosed in Patent Documents 1 to 4 use foil-shaped aluminum, there have been problems such as the foil-shaped aluminum being exposed on the surface of the molded article, deteriorating the appearance, and the conductivity becoming non-uniform for each location of the molded article.

[0007] An object of the present invention is to provide a conductive thermoplastic resin composition that gives a molded article excellent in conductivity, its uniformity, and appearance, and a method for producing the same. Means for Solving the Problems

[0008] The present invention relates to the following [1] to [4]. [1] A conductive thermoplastic resin composition containing, in 100% by mass of the thermoplastic resin composition, 50 to 70% by mass of a thermoplastic resin (A), 28 to 42% by mass of aluminum fine particles (B), and 0 to 10% by mass of carbon black (C); the total amount of the aluminum fine particles (B) and the carbon black (C) in 100% by mass of the thermoplastic resin composition is 38 to 42% by mass; and the average particle diameter of the aluminum fine particles (B) by the sieving method is 250 μm or less. [2] The conductive thermoplastic resin composition according to [1], wherein the thermoplastic resin (A) is a polyolefin resin. [3] A method for producing the conductive thermoplastic resin composition according to [1] or [2], A step of cutting and / or pulverizing a laminate including at least a layer of a first thermoplastic resin and a layer of aluminum foil to obtain pieces of the laminate; a step of adding and mixing a second thermoplastic resin and optional carbon black (C) to the pieces to obtain a mixture; a step of melt-kneading the mixture to form aluminum fine particles (B) from the aluminum foil in the pieces to obtain a conductive thermoplastic resin composition; wherein the first and second thermoplastic resins are of the same type, and the content of the aluminum foil in 100% by mass of the laminate is 55 to 65% by mass. [4] The method for producing a conductive thermoplastic resin composition according to [3], wherein both the first and second thermoplastic resins are polyolefin resins. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a conductive thermoplastic resin composition and a method for producing the same, which give a molded article excellent in conductivity, its uniformity, and appearance. [Embodiments for Carrying Out the Invention]

[0010] In this specification, the content of each component in the composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0011] The conductive thermoplastic resin composition of the present invention contains, in 100% by mass of the thermoplastic resin composition, 50 to 70% by mass of a thermoplastic resin (A), 28 to 42% by mass of aluminum fine particles (B), and 0 to 10% by mass of carbon black (C); the total amount of the aluminum fine particles (B) and the carbon black (C) in 100% by mass of the thermoplastic resin composition is 38 to 42% by mass; and the average particle diameter of the aluminum fine particles (B) by the sieving method is 250 μm or less. By using a thermoplastic resin composition having an average particle diameter of the aluminum fine particles (B) by the sieving method of 250 μm or less and its content in the above range, the conductivity, its uniformity, and the appearance of the obtained molded body can be improved.

[0012] <Thermoplastic resin (A)> The thermoplastic resin (A) is not particularly limited, and examples thereof include polyolefin resins such as polyethylene, polypropylene, polycycloolefin, and 1,2-polybutadiene; halogenated polyolefin resins such as polyvinyl chloride, polyvinylidene chloride, and polytetrafluoroethylene; polyvinyl alcohol; polyester resins such as PET and PBT; and polyamide resins such as polyamide 66, polyamide 6, polyamide 12, polyamide 6 / 66, polyamide 6 / 12, and polyamide 6 / 66 / 12. The thermoplastic resin (A) may be used alone or in combination of two or more.

[0013] From the viewpoints of moldability and ease of availability, the thermoplastic resin (A) is preferably a polyolefin resin, a halogenated polyolefin resin, or a polyamide resin, more preferably a polyolefin resin or a halogenated polyolefin resin, and particularly preferably a polyolefin resin. Among them, from the viewpoints of moldability and ease of availability of raw materials, polypropylene or polyvinyl chloride is preferable, and polypropylene is particularly preferable.

[0014] From the viewpoints of the conductivity, appearance, and mechanical strength of the obtained molded article, the content of the thermoplastic resin (A) in 100% by mass of the thermoplastic resin composition is preferably 50 to 70% by mass, more preferably 55 to 65% by mass, and even more preferably 58 to 62% by mass.

[0015] <Aluminum fine particles (B)> The conductive thermoplastic resin composition contains aluminum fine particles (B) having an average particle diameter of 250 μm or less by a sieving method. By including the aluminum fine particles (B) in the composition, a molded article excellent in conductivity, its uniformity, and appearance can be obtained. The aluminum fine particles (B) may be used alone or in combination of two or more.

[0016] From the viewpoints of the conductivity, its uniformity, and the appearance of the resulting molded article, the average particle diameter of the aluminum fine particles (B) by the sieving method is 250 μm or less. The lower limit of the average particle diameter of the aluminum fine particles (B) by the sieving method is not particularly limited, but it is preferably 100 μm or more.

[0017] In the present invention, the content of the aluminum fine particles (B) is a value obtained by weighing the remaining aluminum fine particles (B) after heating and burning the conductive thermoplastic resin composition. Specifically, put the conductive thermoplastic resin composition into a ceramic crucible, heat it to a temperature below the melting temperature of the aluminum fine particles (B) and up to a temperature at which other components are completely burned or decomposed, completely burn or decompose the thermoplastic resin (A) and the optional carbon black (C) and other components (D), and weigh the remaining aluminum fine particles (B). The content of the aluminum fine particles (B) is a value expressed as a percentage of the mass of the remaining aluminum fine particles (B) with respect to the mass of the conductive thermoplastic resin composition before combustion. Also, in the present invention, the average particle diameter of the aluminum fine particles (B) is a value calculated from the mass of each fraction classified by sieving the remaining aluminum fine particles (B). Specifically, use a plurality of stainless steel test sieves (manufactured by Naka Rika Kiki Seisakusho Co., Ltd., φ75 mm, mesh openings 2,000 μm, 1,400 μm, 1,000 μm, 600 μm, 425 μm, 300 μm, 180 μm, and 90 μm), and sieve the remaining aluminum fine particles (B) while applying vibration. Next, weigh the mass of the residue on the sieve and the mass obtained in the receiver after passing through all the sieves. Plot and interpolate the mesh opening diameter and the passing mass of each sieve, and take the mesh opening diameter when the passing mass is 50% as the average particle diameter of the aluminum fine particles (B).

[0018] If the average particle diameter of the aluminum fine particles (B) by the sieving method is 250 μm or less, the shape of the aluminum fine particles (B) is not particularly limited, and it may be approximately spherical. In addition, as will be described later, in the production of the conductive thermoplastic resin composition, an aluminum foil or a laminate containing at least an aluminum foil may be used as a raw material, and aluminum fine particles (B) may be formed from the aluminum foil during the production process. In this case, it is preferable that the aluminum foil does not remain in a foil shape, but has a granular shape as a whole due to bending, rounding, etc.

[0019] From the viewpoints of the conductivity, appearance, and mechanical strength of the obtained molded article, the content of the aluminum fine particles (B) in 100% by mass of the thermoplastic resin composition is 28 to 42% by mass, and more preferably 30 to 40% by mass. When the content of the aluminum fine particles (B) is less than 28% by mass, the conductivity of the molded article becomes insufficient, and when it exceeds 42% by mass, the moldability of the composition and the mechanical strength of the molded article decrease.

[0020] <Carbon black (C)> The conductive thermoplastic resin composition may optionally contain carbon black (C). By including carbon black (C) in the composition, the conductivity and its uniformity of the obtained molded article can be further improved. Carbon black (C) may be used alone or in combination of two or more.

[0021] Carbon black (C) is not particularly limited, and furnace black, channel black, acetylene black, thermal black, etc. can be used.

[0022] From the viewpoint of improving the conductivity of the molded article, the average particle diameter of carbon black (C) is preferably 5 to 100 μm, and more preferably 10 to 70 μm. In the present invention, the average particle diameter of carbon black is a catalog value.

[0023] From the viewpoint of improving the conductivity of the molded article, the DBP absorption amount of carbon black (C) is preferably 100 to 600 cm 3 / 100 g, and more preferably 150 to 600 cm 3It is more preferably 100 g. In the present invention, the DBP absorption amount is a value measured according to JIS K6217-4.

[0024] From the viewpoint of improving the conductivity of the molded product, the BET specific surface area of carbon black (C) is preferably 50 m 2 / g or more, and more preferably 200 m 2 / g or more. In the present invention, the BET specific surface area is a value measured by the nitrogen adsorption method according to JIS K6217-2.

[0025] From the viewpoint of improving the conductivity of the molded product, the content of carbon black (C) in 100% by mass of the thermoplastic resin composition is preferably 0 to 10% by mass, and more preferably 5 to 10% by mass from the viewpoint of reducing the volume resistivity of the injection molded product.

[0026] From the viewpoints of the conductivity, appearance, and mechanical strength of the obtained molded product, the total content of aluminum fine particles (B) and carbon black (C) in 100% by mass of the thermoplastic resin composition is preferably 38 to 42% by mass. If the total content of aluminum fine particles (B) and carbon black (C) is less than 38% by mass, the conductivity of the molded product will be insufficient, and if it exceeds 42% by mass, the moldability of the composition and the mechanical strength of the molded product will decrease.

[0027] <Other components (D)> The conductive thermoplastic resin composition can contain other components (D) as long as the effects of the present invention are not impaired. Examples of the other components (D) include, for example, aluminum fine particles other than aluminum fine particles (B), metal fine particles other than aluminum, inorganic fine particles other than metals, organic fine particles other than carbon black, antioxidants, crystal nucleating agents, crystallization accelerators, plasticizers, heat-resistant agents, weather-resistant agents, flame retardants, flame retardant aids, mold release agents, fluidity modifiers, and the like.

[0028] <Method for producing a conductive thermoplastic resin composition> The method for producing the conductive thermoplastic resin composition is not particularly limited. For example, a method of melt-kneading a thermoplastic resin (A), aluminum fine particles (B), optional carbon black (C), and other components (D) using a known melt-kneading machine such as a single-screw or twin-screw extruder, Banbury mixer, kneader, and mixing roll; a method of melt-kneading a thermoplastic resin (A), foil-shaped aluminum, optional carbon black (C), and other components (D) using the above melt-kneading machine, and forming aluminum fine particles (B) from the foil-shaped aluminum during the melt-kneading to obtain a conductive thermoplastic resin composition; and the like can be mentioned. In the case of the latter method, it is preferable that the foil-shaped aluminum is in the form of a laminate together with the layer of the thermoplastic resin. By using such a laminate, it becomes possible to improve the compatibility between the thermoplastic resin (A) and the aluminum fine particles (B) formed from the foil-shaped aluminum, and the conductivity, uniformity, and appearance of the resulting molded article can be made good.

[0029] Another aspect of the present invention is a method for producing a conductive thermoplastic resin composition, comprising a step of cutting and / or pulverizing a laminate including at least a layer of a first thermoplastic resin and a layer of aluminum foil to obtain pieces of the laminate; a step of adding and mixing a second thermoplastic resin and optional carbon black (C) to the pieces to obtain a mixture; and a step of melt-kneading the mixture to form aluminum fine particles (B) from the aluminum foil in the pieces to obtain a conductive thermoplastic resin composition, wherein the first and second thermoplastic resins are of the same type, and the content of the aluminum foil in 100% by mass of the laminate is 55 to 65% by mass.

[0030] The first step is a step of cutting and / or pulverizing a laminate including at least a layer of a first thermoplastic resin and a layer of aluminum foil to obtain pieces of the laminate. From the viewpoint of improving the compatibility between the thermoplastic resins and making the conductivity, uniformity, and appearance of the molded product good, it is preferable that the first thermoplastic resin and the second thermoplastic resin in the second step are resins of the same type. As the first and second thermoplastic resins, the resins exemplified in the item <Thermoplastic resin (A)> can be used.

[0031] In the present invention, two or more resins corresponding to polyolefin resins are resins of the same type as each other. For example, polyethylene and polypropylene are resins of the same type. The same applies to halogenated polyolefin resins, polyester resins, and polyamide resins. From the viewpoints of moldability and ease of availability, it is preferable that both the first and second thermoplastic resins are polyolefin resins, halogenated polyolefin resins, or polyamide resins, more preferably polyolefin resins or halogenated polyolefin resins, and particularly preferably polyolefin resins. Among them, it is preferable that both the first and second thermoplastic resins are polypropylene or polyvinyl chloride, and particularly preferably polypropylene.

[0032] The laminate including at least the layer of the first thermoplastic resin and the layer of the aluminum foil is not particularly limited as long as these two layers are included. For example, those produced by heating the thermoplastic resin and the aluminum foil at a temperature equal to or higher than the softening point of the thermoplastic resin and then performing pressure bonding can be used. If necessary, an adhesive layer may be provided between the layer of the thermoplastic resin and the layer of the aluminum foil. In addition, as such a laminate, a drug packaging (PTP) sheet, waste materials of the drug packaging (PTP) sheet generated during or after the production or use of the drug packaging (PTP) sheet, an aluminum laminate sheet for food packaging and its waste materials, an aluminum laminate sheet for semiconductor packaging and its waste materials, an aluminum vapor deposition sheet and its waste materials, etc. may be used. In the case of the drug packaging (PTP) sheet and its waste materials, it may contain a thermoplastic resin corresponding to the pocket portion for storing the drug. By using waste materials of the drug packaging (PTP) sheet, the aluminum laminate sheet for food packaging, the aluminum laminate sheet for semiconductor packaging, and the aluminum vapor deposition sheet, it is also possible to contribute to environmental protection and recycling.

[0033] The content of the aluminum foil in the laminate is preferably 55 to 65% by mass in order to achieve the aluminum content rate in the conductive thermoplastic resin composition of the present invention. Further, the content of the layer of the first thermoplastic resin in the laminate is preferably 35 to 45% by mass.

[0034] The shape of the laminate is not particularly limited, but is preferably sheet-like. The total thickness of the laminate is preferably 10 to 1,000 μm, more preferably 20 to 800 μm, and even more preferably 50 to 500 μm. In the case of the drug packaging (PTP) sheet and its waste materials, since voids are present in the pocket portion for storing the drug, the apparent thickness becomes thick, but it is the thickness without considering the thickness of such portions.

[0035] In the first step, the laminate is cut and / or pulverized to obtain pieces of the laminate. The shape and size of the pieces are not particularly limited. For example, when the laminate is sheet-like, the shape of the pieces when viewed from the thickness direction may be any shape such as a polygon such as a triangle or a quadrilateral; a circle, an ellipse, an irregular shape, etc. The size of the pieces is preferably such that the average area of the plane when viewed from the thickness direction is 0.3 to 50.0 mm 2 and more preferably 3.0 to 30.0 mm 2More preferably, the average thickness of the aluminum foil in the flakes is preferably 0.005 to 80 μm. By using flakes having such a shape and size, in the third step, when the mixture is melt-kneaded, aluminum fine particles (B) having an average particle diameter of 250 μm or less can be easily formed from the aluminum foil in the flakes.

[0036] Examples of the method for cutting and / or pulverizing the laminate include methods using cutting devices such as shredders, slitters, cutters, or pulverizing devices such as mixers and grinders. When pulverization is performed using a pulverizing device, the stirring speed is preferably 500 to 30,000 rpm, more preferably 1,000 to 25,000 rpm, and still more preferably 3,000 to 20,000 rpm. Also, the stirring time is preferably 1 to 10 minutes, more preferably 2 to 5 minutes. The stirring temperature may be determined according to the first thermoplastic resin, but is preferably -80 to 80°C, more preferably -80 to 60°C. By stirring within the above temperature range, melting of the first thermoplastic resin due to heat generation during stirring can be suppressed.

[0037] The second step is a step of adding and mixing a second thermoplastic resin and optional carbon black (C) to the flakes to obtain a mixture. The flakes, the second thermoplastic resin, and the carbon black (C) are preferably formulated such that the total amount of the first and second thermoplastic resins in 100% by mass of the mixture is 50 to 70% by mass, the content of the aluminum foil is 28 to 42% by mass, the content of the carbon black (C) is 0 to 10% by mass, and the total amount of the aluminum foil and the carbon black (C) is 38 to 42% by mass. Other components (D) may be added to the mixture. The method for mixing the flakes, the second thermoplastic resin, and the optional carbon black (C) and other components (D) is not particularly limited, and for example, various blenders can be used.

[0038] The third step is a step of melt-kneading the mixture to form aluminum fine particles (B) from the aluminum foil in the flakes, thereby obtaining a conductive thermoplastic resin composition. In this step, aluminum fine particles (B) having an average particle diameter of 250 μm or less are formed from the aluminum foil in the flakes. Examples of the melt-kneading apparatus include a batch mixer (for example, a plastcorder manufactured by Brabender), a single-screw or twin-screw melt-kneading apparatus, etc. From the viewpoint of forming aluminum fine particles (B) having an average particle diameter of 250 μm or less from the aluminum foil in the flakes, the melt-kneading conditions are preferably the following conditions. That is, when using a batch mixer, the screw rotation speed is preferably 2 to 100 rpm, more preferably 5 to 80 rpm, and the kneading time is preferably 1 to 20 minutes, more preferably 2 to 10 minutes. When using a twin-screw melt-kneading apparatus, the screw rotation speed is preferably 20 to 600 rpm, more preferably 50 to 500 rpm, and the extrusion amount during melt-kneading is preferably 10 to 100 kg / Hr, more preferably 15 to 80 kg / Hr. Also, the kneading temperature is preferably (the melting point of the thermoplastic resin) to (the melting point of the thermoplastic resin + 80°C), more preferably (the melting point of the thermoplastic resin) to (the melting point of the thermoplastic resin + 70°C). For example, when the thermoplastic resin (A) is polypropylene, the kneading temperature is preferably 160 to 240°C, more preferably 160 to 230°C. Also, when the thermoplastic resin is polyamide 6, the kneading temperature is preferably 225 to 305°C, more preferably 225 to 295°C.

[0039] The conductive thermoplastic resin composition produced by the above method can be made into forms such as pellets, beads, powders, pastes, films, etc. by known methods.

Examples

[0040] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0041] [Evaluation Method] 1. Content of aluminum fine particles (B) in the thermoplastic resin composition 2 g of the thermoplastic resin composition was placed in a ceramic crucible, and the thermoplastic resin (A) and the optional carbon black (C) were completely burned or decomposed, and the remaining aluminum fine particles (B) were weighed. The content (mass %) of the aluminum fine particles (B) was calculated as the mass of the remaining aluminum fine particles (B) with respect to the mass of the thermoplastic resin composition before combustion or decomposition.

[0042] 2. Average particle diameter of aluminum fine particles (B) Using a plurality of stainless steel test sieves (manufactured by Naka Rika Kiki Seisakusho Co., Ltd., φ75 mm, mesh openings 2,000 μm, 1,400 μm, 1,000 μm, 600 μm, 425 μm, 300 μm, 180 μm, and 90 μm), the remaining aluminum fine particles (B) obtained in 1 above were sieved while applying vibration. Next, the mass of the residue on the sieve and the mass obtained in the receiver passing through all the sieves were weighed. The mesh opening diameter and the passing mass of each sieve were plotted and interpolated, and the mesh opening diameter when the passing mass became 50% was determined as the average particle diameter of the aluminum fine particles (B).

[0043] 3. Preparation of dumbbell test pieces Using the thermoplastic resin compositions of the examples and comparative examples respectively, in accordance with JIS K 7139:2000 A1, injection molding was carried out under the conditions of an extruder temperature of 210 °C and a mold temperature of 40 °C to obtain dumbbell test pieces.

[0044] 4. Measurement of volume resistivity and evaluation of uniformity of molded products At 23 °C and 50% RH, the dumbbell test piece obtained in 3 above was placed on a 26 cm square metal plate electrode, and a φ5 cm metal electrode was further placed on the test piece. Using an insulation resistance meter (manufactured by Kyoritsu Electric Instrument Co., Ltd.), a voltage of 500 V was applied between the two electrodes to measure the resistance value, and the volume resistivity was determined from the contact area between the dumbbell test piece and the electrode and the thickness of the dumbbell test piece. The volume resistivity was measured at four locations per lot, and the average of the four measured values was taken as the volume resistivity of the molded product. The acceptance criterion for the volume resistivity was set at 10,000 Ω·cm or less. Also, the ratio of the measured values that met the acceptance criterion among the four measured values was taken as the uniformity value. The acceptance criterion for uniformity was set at 100%.

[0045] 5. Evaluation of the Appearance of the Molded Product The dumbbell test pieces obtained in the above 3 were visually confirmed, and the appearance (surface roughness) of the molded product was judged according to the following criteria. ○: The surface of the molded product is smooth and the appearance is good. ×: The surface of the molded product has roughness and the appearance is poor.

[0046] [Raw Materials Used] In the examples and comparative examples, the following raw materials were used. · Laminate containing a layer of polypropylene and a layer of aluminum foil: provided by UACJ Corporation (aluminum content: 60% by mass, polypropylene content: 40% by mass) · Polypropylene: manufactured by Prime Polymer Co., Ltd., J106G · Carbon black: manufactured by Cabot Corporation, VULCAN (registered trademark) VXC72GP

[0047] [Crushing of the Laminate] A laminate containing a layer of polypropylene and a layer of aluminum foil was continuously fed into a crusher (manufactured by Horai Co., Ltd.) at a rate of 20 kg / h and crushed while controlling the temperature inside the equipment to be less than 60°C to obtain fine pieces of the laminate.

[0048] Example 1 The fine pieces obtained by crushing the laminate, polypropylene, and carbon black were mixed at a mass ratio of 58 / 37 / 5. The resulting mixture was fed into a twin-screw extruder (manufactured by MSC Co., Ltd.) at a rate of 15 kg / Hr, extruded into strands under the conditions of 230°C and 160 rpm, then introduced into a water tank, cooled, cut, and vacuum dried to obtain a thermoplastic resin composition. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was granular and there was no foil-shaped aluminum. The content and average particle diameter of the aluminum fine particles (B) in the thermoplastic resin composition were 35% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Example 1 and the average particle diameter of the aluminum fine particles (B) are shown in Table 1.

[0049] Example 2 The thermoplastic resin composition of Example 2 was obtained in the same manner as in Example 1, except that the amount (mass ratio) of the chips obtained by crushing the laminate and polypropylene was changed to 67 / 33 and carbon black was not used. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was granular and there was no foil-shaped aluminum. The content and average particle diameter of the aluminum fine particles (B) in the thermoplastic resin composition were 40% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Example 2 and the average particle diameter of the aluminum fine particles (B) are shown in Table 1.

[0050] Example 3 The thermoplastic resin composition of Example 3 was obtained in the same manner as in Example 1, except that the amount (mass ratio) of the chips, polypropylene and carbon black obtained by crushing the laminate was changed to 50 / 40 / 10. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was granular and there was no foil-shaped aluminum. The content and average particle diameter of the aluminum fine particles (B) in the thermoplastic resin composition were 30% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Example 3 and the average particle diameter of the aluminum fine particles (B) are shown in Table 1.

[0051] Comparative Example 1 The thermoplastic resin composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the uncrushed laminate was used as it was instead of the chips obtained by crushing the laminate. The content and average particle size of the aluminum fine particles (B) in the thermoplastic resin composition were 35% by mass and 900 μm, respectively. The formulation of the thermoplastic resin composition of Comparative Example 1 and the average particle size of the aluminum fine particles (B) are shown in Table 1.

[0052] Comparative Example 2 The amount of the pieces obtained by crushing the laminate and polypropylene (mass ratio) was changed to 58 / 42, and a thermoplastic resin composition of Comparative Example 2 was obtained in the same manner as in Example 1 except that carbon black was not used. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was in a granular form and no foil-like aluminum was present. The content and average particle size of the aluminum fine particles (B) in the thermoplastic resin composition were 35% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Comparative Example 2 and the average particle size of the aluminum fine particles (B) are shown in Table 1.

[0053] Comparative Example 3 A thermoplastic resin composition of Comparative Example 3 was obtained in the same manner as in Example 1 except that the amounts of the pieces obtained by crushing the laminate, polypropylene, and carbon black (mass ratio) were changed to 58 / 41 / 1. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was in a granular form and no foil-like aluminum was present. The content and average particle size of the aluminum fine particles (B) in the thermoplastic resin composition were 35% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Comparative Example 3 and the average particle size of the aluminum fine particles (B) are shown in Table 1.

[0054] Comparative Example 4 A thermoplastic resin composition of Comparative Example 4 was obtained in the same manner as in Example 1 except that the amounts of the pieces obtained by crushing the laminate, polypropylene, and carbon black (mass ratio) were changed to 50 / 45 / 5. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was in granular form and there was no foil-like aluminum. The content and average particle diameter of the aluminum fine particles (B) in the thermoplastic resin composition were 30% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Comparative Example 4 and the average particle diameter of the aluminum fine particles (B) are shown in Table 1.

[0055] Comparative Example 5 A thermoplastic resin composition of Comparative Example 5 was obtained in the same manner as in Example 1, except that the amounts (mass ratio) of the chips obtained by crushing the laminate, polypropylene, and carbon black were changed to 42 / 48 / 10. When the cross-section of the thermoplastic resin composition was observed by SEM, it was confirmed that the aluminum in the thermoplastic resin composition was in granular form and there was no foil-like aluminum. The content and average particle diameter of the aluminum fine particles (B) in the thermoplastic resin composition were 25% by mass and 250 μm, respectively. The formulation of the thermoplastic resin composition of Comparative Example 5 and the average particle diameter of the aluminum fine particles (B) are shown in Table 1.

[0056] Using the thermoplastic resin compositions of Examples 1 to 3 and Comparative Examples 1 to 5 respectively, dumbbell test pieces were prepared, and the volume resistivity, uniformity, and appearance of the molded products were evaluated. The results are shown in Table 1. In Table 1, "not energized" indicates that the volume resistivity could not be measured.

[0057]

Table 1

[0058] It can be seen from Table 1 that the thermoplastic resin compositions of Examples 1 to 3 are all excellent in the conductivity, uniformity, and appearance of the molded products. Although Comparative Example 1 had the same formulation as Example 1, the appearance of the molded product deteriorated because the average particle diameter of the aluminum fine particles was 900 μm. In Comparative Examples 2, 4, and 5, where the total amount of the aluminum fine particles and carbon black in 100% by mass of the thermoplastic resin composition was 35% by mass, the volume resistivity of the molded product was high. In Comparative Example 3, where the total amount of the aluminum fine particles and carbon black in 100% by mass of the thermoplastic resin composition was 36% by mass, although the volume resistivity of the molded product was good, its uniformity was poor and the variation depending on the measurement location was large.

Industrial Applicability

[0059] The conductive thermoplastic resin composition of the present invention is suitably used for various applications that require conductivity.

Claims

1. In 100% by mass of the thermoplastic resin composition, it contains 50 to 70% by mass of a thermoplastic resin (A), 28 to 42% by mass of aluminum fine particles (B), and 0 to 10% by mass of carbon black (C). The total amount of the aluminum fine particles (B) and the carbon black (C) in 100% by mass of the thermoplastic resin composition is 38 to 42% by mass. A conductive thermoplastic resin composition, wherein the average particle diameter of the aluminum fine particles (B) by the sieving method is 250 μm or less.

2. The conductive thermoplastic resin composition according to Claim 1, wherein the thermoplastic resin (A) is a polyolefin resin.

3. A method for producing the conductive thermoplastic resin composition according to Claim 1 or 2, comprising: a step of cutting and / or pulverizing a laminate including at least a layer of a first thermoplastic resin and a layer of an aluminum foil to obtain pieces of the laminate; a step of adding and mixing a second thermoplastic resin and optional carbon black (C) to the pieces to obtain a mixture; a step of melt-kneading the mixture to form aluminum fine particles (B) from the aluminum foil in the pieces and obtain a conductive thermoplastic resin composition. The method includes that the first and second thermoplastic resins are of the same type, and the content of the aluminum foil in 100% by mass of the laminate is 55 to 65% by mass.

4. The method for producing the conductive thermoplastic resin composition according to Claim 3, wherein both the first and second thermoplastic resins are polyolefin resins.

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