JP7135825B2 - Resin composition and resin molded parts - Google Patents

Description

The present invention relates to resin compositions and resin molded parts.

BACKGROUND ART In recent years, technology for reducing the weight of automobile parts has attracted attention in order to improve the fuel efficiency of automobiles and electrify automobiles. As one of such techniques, replacement of metal parts with resin parts is being studied. Among resins, carbon fiber reinforced thermoplastic (CFRTP), which has a strength close to that of metal but is lighter than metal, has attracted particular attention. To give a specific example, CFRTP has a strength close to that of an aluminum alloy, but has a lower density than aluminum (the density of aluminum is 2.7 g/cm ³ , whereas the density of CFRTP is 1.5 g/cm 3 ). 0-1.5 g/cm ³ ). Furthermore, CFRTP can be injection molded like general plastics, so it has the advantage of being able to produce parts with complicated three-dimensional shapes.

By the way, addition of various fillers to CFRTP to improve its functions or to impart further functions is also under study. For example, Patent Literature 1 discloses “a carbon fiber reinforced plastic material in which carbon fibers and a nanofiller are dispersed in a non-oriented manner in the carbon fiber reinforced plastic material”.

Taking the application to automobile parts as an example, CFRTP should be provided with a shielding function to block electromagnetic noise generated from electrical parts and a heat conduction function to dissipate heat generated from the same electrical parts. is being considered.

As for the shielding function, the general CFRTP has a volume resistance value of about 10 ³ to 10 ⁶ Ω·cm, and has only an insufficient shielding function. Therefore, a method of improving the shield function by adding a conductive filler to the CFRTP to impart conductivity and converting the incident electromagnetic wave into an induced current inside the CFRTP is adopted. Regarding this point, Patent Document 2 discloses that "(A) 100 parts by mass of thermoplastic resin, (B) 1 to 20 parts by mass of carbon fiber, and (C) 1 to 20 parts by mass of metal fiber, the volume of the molded body A conductive resin composition having a specific resistance value of 10 ³ Ω·cm or less” is disclosed.

As for the heat-conducting function, the general CFRTP has a heat conductivity of 1 W/m·K, and has an insufficient heat-conducting function. Therefore, a method of adding a thermally conductive filler to CFRTP to impart electrical conductivity to improve the thermal conduction function is adopted. Regarding this point, Patent Document 3 discloses that "(A) 1 to 30 parts by weight of carbon fiber, ( B) a fiber-reinforced thermoplastic resin molded product containing 1 to 40 parts by weight of a ceramic filler and (C) 30 to 98 parts by weight of a thermoplastic resin, and (A) having a carbon fiber weight average fiber length of 300 to 3000 μm. disclosed.

Japanese Patent No. 6143107 Japanese Patent Application Laid-Open No. 2006-045330 JP 2016-190922

However, none of the aforementioned prior art documents provided CFRTP with both shielding and heat conducting functions.

In addition, generally, in order to impart a shielding function and a heat conducting function to CFRTP, it is necessary to increase the content of the filler. Then, since the filler is usually a material with a high specific gravity, the specific gravity of the CFRTP itself also increases. In other words, if the technique of increasing the filler content is adopted, instead of imparting shielding and heat-conducting functions to CFRTP, there is a tendency for CFRTP to lose its advantage of light weight.

An object of one aspect of the present invention is to provide a resin composition imparted with sufficient shielding function and heat conducting function. The "sufficient shielding function and heat conducting function" referred to here are appropriately set according to the application of the resin composition, and are not restricted to specific numerical values.

In order to solve the above problems, a resin composition according to one aspect of the present invention is a resin composition containing a thermoplastic resin, carbon fibers and a conductive filler; It is distributed like a network in the plastic resin.

Further, a resin composition according to another aspect of the present invention is a resin composition containing a thermoplastic resin, carbon fibers and a conductive filler; The conductive filler is agglomerated in the vicinity of the carbon fiber.

In the resin composition having the above structure, the conductive filler is distributed in a mesh pattern in the thermoplastic resin. That is, it has a shape in which a network of conductive filler is developed in the resin matrix. Electric current and heat can be conducted through this network of conductive fillers. As a result, the resin composition is endowed with a shielding function and a heat conducting function.

"The conductive filler is distributed in a network" means that the distribution of the conductive filler in the thermoplastic resin has linear regions and branch points, and two or more linear regions are present at the branch points. means that they intersect. Whether or not the conductive filler is distributed in a network can be determined, for example, by taking an electron microscope image (SEM image, etc.) from a resin composition sample and using known image processing software (Image J, etc.). can do.

"The conductive filler is aggregated in the vicinity of the carbon fiber" means that the distribution of the conductive filler in the resin composition is localized in the vicinity of the carbon fiber. Whether or not the distribution of the conductive filler in the resin composition is biased toward the vicinity of the carbon fiber can be determined, for example, by examining the "area near the carbon fiber" and the " The amount of the conductive filler contained in the former is three times or more that of the conductive filler contained in the latter. Known image processing software (such as Image J) can be used for such determination.

“The carbon fibers are defibrated” means that the carbon fibers are not agglomerated to form a bundle. Whether or not the carbon fibers are defibrated can be determined, for example, from morphological observation using an electron microscope image (SEM image, etc.).

“Isotropically dispersed” means that the distribution of carbon fibers has no orientation (or little orientation). Carbon fibers isotropically dispersed in the resin composition are oriented in random directions. Whether or not the carbon fibers are isotropically dispersed can be determined, for example, by measuring local thermal conductivity in the sample. For example, a fiber orientation evaluation system TEFOD (manufactured by Bethel Co., Ltd.) can be used to measure the local thermal conductivity in the sample. Alternatively, it is possible to determine whether or not the carbon fibers are isotropically dispersed by morphological observation using an electron microscope image (such as an SEM image).

In one embodiment, the volume resistivity of the resin composition measured according to JIS K 7194 is 10 ² Ω·cm or less. The volume resistivity of the resin composition is more preferably 10 ⁰ Ω·cm or less, more preferably 10 ⁻¹ Ω·cm or less. Although the lower limit of the volume resistance is not particularly limited, it can be, for example, 10 ⁻⁵ Ω·cm.

In one embodiment, the shielding effect of the resin composition measured by the KEC method is 30 dB or more at 1 MHz to 10 MHz. More preferably, the shielding effect of the resin composition is 30 dB or more at 1 MHz to 1 GHz. Although the upper limit of the shielding effect is not particularly limited, it can be 80 dB or less at 1 MHz to 1 GHz, for example.

It can be said that the resin composition having the above structure has a sufficient shielding function when considering application to automotive power modules, motor peripheral parts, electronic devices, and the like.

In one embodiment, the thermal conductivity of the resin composition is 2 W/m·K or more as measured by a disc heat flow meter method (ASTM E1530). More preferably, the thermal conductivity of the resin composition is 5 W/m·K or more. Although the upper limit of the thermal conductivity of the resin composition is not particularly limited, it can be, for example, 20 W/m·K or less.

In one embodiment, the thermal conductivity of the conductive filler measured by a laser flash method is 10 W/m·K or more. More preferably, the conductive filler has a thermal conductivity of 100 W/m·K or more. Although the upper limit of the thermal conductivity of the conductive filler is not particularly limited, it can be, for example, 10,000 W/m·K or less.

It can be said that the resin composition having the above structure has a sufficient heat conduction function when considering application to vehicle power modules, motor peripheral parts, electronic devices, and the like.

In one embodiment, the conductive filler is one or more selected from the group consisting of metal-based fillers, metal oxide-based fillers and carbon-based fillers. Preferably, the conductive filler is one or more selected from the group consisting of metal-based fillers and carbon-based fillers.

These conductive fillers are preferable in that they hardly impair the lightness of the resin composition. In addition, a mode in which the conductive filler is selected from the group consisting of metal-based fillers and carbon-based fillers is preferable from the viewpoint of achieving both a shielding function and a heat-conducting function.

In one embodiment, when the thermoplastic resin is 100 parts by weight, the content of the carbon fiber is 5 to 70 parts by weight. More preferably, the carbon fiber content is 10 to 45 parts by weight.

By setting the carbon fiber content within the above range, a network of the conductive filler is easily formed, and sufficient shielding and heat conduction functions can be obtained. Conversely, if the carbon fiber content is less than 5 parts by weight, the conductive filler network tends to be poorly formed. On the other hand, if the carbon fiber content is more than 70 parts by weight, the conductive filler tends to be scattered on the surface of the carbon fiber and the network of the conductive filler tends to be cut.

Regarding a viewpoint different from the network of the conductive filler, if the content of the carbon fiber is less than 5 parts by weight, the strength of the resin composition tends to be insufficient. Similarly, when the carbon fiber content is more than 70 parts by weight, it tends to be difficult to isotropically disperse the carbon fibers during the production of the resin composition, and the melt viscosity increases to obtain a good molded product. tends to be difficult.

In one embodiment, when the thermoplastic resin is 100 parts by weight, the content of the conductive filler is 3 to 80 parts by weight. More preferably, the content of the conductive filler is 5 to 30 parts by weight.

By setting the content of the conductive filler within the above range, a network of the conductive filler is easily formed, and sufficient shielding function and heat conducting function can be obtained. Conversely, if the content of the conductive filler is less than 3 parts by weight, it becomes difficult to form a network of the conductive filler, and the shielding function and the heat-conducting function tend to be inferior. Moreover, when the content of the conductive filler exceeds 80 parts by weight, the conductive filler cannot be dispersed well during the production of the resin composition, and the resin composition tends to become brittle.

By the way, when the amount of the conductive filler added increases, the specific gravity of the resin composition increases, so that the molded article using the resin composition becomes heavy. From such a point of view, it is preferable to appropriately adjust the content of the conductive filler according to the type of the conductive filler. The upper limit of the content of the conductive filler may be, for example, 40 parts by weight, 50 parts by weight, 60 parts by weight, or 70 parts by weight.

In one embodiment, the resin composition has a density of less than 2.68 g/cm ³ . More preferably, the density of the resin composition is less than 1.98 g/ ^cm3 . Although the lower limit of the density of the resin composition is not particularly limited, it can be, for example, 0.90 g/cm ³ or more.

The resin composition having the above structure is lighter than metal materials. Therefore, it is suitable as a material to replace metal.

A resin molded part comprising a resin composition according to one embodiment of the present invention is also included within the scope of the present invention. Such resin-molded products are used, for example, as parts constituting vehicle-mounted power modules, motor peripheral parts, electronic devices (sensors, switches, DC converters, etc.).

According to one aspect of the present invention, there is provided a resin composition imparted with sufficient shielding function and heat conducting function.

(a) is a schematic diagram illustrating the structure of a resin composition according to one embodiment of the present invention. (b) is an enlarged view of area A shown in (a).

Hereinafter, an embodiment (hereinafter also referred to as "this embodiment") according to one aspect of the present invention will be described. However, the invention is not limited to these embodiments. Unless otherwise specified in this specification, "A to B" representing a numerical range means "A or more and B or less".

§1 Application Example An outline of a resin composition according to one embodiment of the present invention will be described with reference to FIG. FIG. 1(a) is a schematic diagram illustrating the structure of a resin composition according to one embodiment. In the resin composition 10, the thermoplastic resin 3 serves as a matrix, and carbon fibers 1 and conductive fillers 2 are contained therein.

Here, the conductive fillers 2 are aggregated near the carbon fibers 1 . This is shown more clearly in FIG. 1(b). FIG. 1(b) is an enlarged view of region A in FIG. That is, in (a) of FIG. 1 , the conductive filler 2 is aggregated in the black region which is a rectangular outline representing the carbon fiber 1 .

The carbon fibers 1 are isotropically distributed in the thermoplastic resin 3 in a defibrated state. As described above, the conductive filler 2 is aggregated and distributed near the carbon fibers 1 . As a result, the conductive fillers 2 in the resin composition 10 are distributed in a mesh pattern. That is, a network is formed in which the conductive fillers 2 are in contact with each other. Through the network of the conductive filler 2, it becomes possible to conduct electric current and conduct heat, and as a result, the resin composition 10 obtains a shielding function and a heat conducting function.

Since the resin composition 10 can localize the conductive fillers 2 in a mesh shape, it is not necessary to increase the conductive fillers 2 in order to provide the shielding function and the heat conducting function. Therefore, the resin composition 10 can acquire a shielding function and a heat conducting function while maintaining lightness.

Here, whether or not the distribution of the carbon fibers 1 and the conductive fillers 2 in the resin composition 10 is included in the scope of the present invention can be clearly determined by, for example, a known image processing technique. Furthermore, the physical properties of the resin composition 10 can make the determination more reliable. For example, the fact that the resin composition 10 has one or more of the following physical properties (i) to (iii) means that "the distribution of the carbon fibers 1 and the conductive filler 2 in the resin composition 10 is the present invention. be included in the category of

(i) The volume resistivity measured according to JIS K 7194 is 10 ² Ω·cm or less.

(ii) The shielding effect measured by the KEC method is 30 dB or more at 1 MHz to 10 MHz.

(iii) Thermal conductivity measured by a disk heat flow meter method is 2 W/m·K or more.

By the way, as a method of distributing the conductive substance along the carbon fibers, it is also conceivable to use carbon fibers coated with a conductive substance as the material. However, it is considered that this method cannot obtain the effect of the present invention. This is because carbon fibers at the material stage usually exist as undisentangled bundles. Even if the surface of the unfibrillated carbon fibers is covered, many uncovered surfaces remain after defibration of the carbon fibers.

On the other hand, in the resin composition according to one aspect of the present invention, the carbon fibers and the conductive filler aggregate due to interaction based on affinity. As a result, a structure in which the conductive filler is locally distributed near the carbon fibers can be obtained.

§2 Configuration example [Thermoplastic resin]
Examples of thermoplastic resins contained in the resin composition according to one embodiment of the present invention include olefin-based resins, amide-based resins, ester-based resins, ether-based resins, nitrile-based resins, methacrylate-based resins, and vinyl-based resins. Examples include resins, cellulose resins, fluorine resins, and imide resins. These resins may contain only one type, may contain two or more types, or may be a copolymer of these resins.

Examples of olefinic resins include high-density polyethylene, low-density polyethylene, ultra-high molecular weight polyethylene, and polypropylene (isotactic polypropylene, syndiotactic polypropylene, etc.).

Examples of amide resins include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon MXD6, nylon 6T, and copolymers thereof.

Examples of ester resins include polylactic acid, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyethylene isophthalate, polyarylate, polybutylene naphthalate, liquid crystal polyester, and copolymers thereof.

Examples of ether-based resins include polyacetal, polyphenylene oxide, polyphenylene sulfide, polysulfone, and polyetheretherketone.

Examples of nitrile resins include polyacrylonitrile and polymethacrylonitrile.

Examples of methacrylate resins include polymethyl methacrylate and polyethyl methacrylate.

Examples of vinyl resins include vinyl acetate, polyvinyl alcohol, polyvinylidene chloride, and polyvinyl chloride.

Examples of cellulosic resins include cellulose acetate and cellulose acetate butyrate.

Examples of fluorine-based resins include polyvinylidene fluoride, polyvinyl fluoride, and polychlorotrifluoroethylene.

Examples of imide-based resins include aromatic polyimides and polyacetals.

When thermoplastic resins are used for automobile parts, crystalline thermoplastic resins, which are excellent in chemical resistance and oil resistance, are preferred. In one embodiment of the present invention, crystalline resins such as high-density polyethylene, polypropylene, polybutylene terephthalate, polyethylene terephthalate, polyacetal, polyphenylene sulfide, and polyetheretherketone can be suitably used.

[Carbon fiber]
Known carbon fibers such as pitch-based, rayon-based, and PAN-based carbon fibers can be used in the resin composition according to one embodiment of the present invention. Carbon fiber has a function of increasing the rigidity of the resin composition and a function of serving as a scaffold for network formation of the conductive filler.

A virgin material or a recycled material may be used for the carbon fiber. A carbon fiber recycled material is obtained by separating a matrix resin from a carbon fiber reinforced plastic (CFRP) by, for example, a thermal decomposition method, a chemical dissolution method, a supercritical fluid method, or the like.

The length of carbon fiber is not particularly limited. In order to disperse the carbon fibers in the thermoplastic resin, the length is preferably 30 mm or less. Moreover, the length is preferably 0.1 mm or more from the viewpoint of serving as a scaffold for network formation of the conductive filler. In addition, the length of the carbon fiber may have a distribution, and in this case, the carbon fiber having a length not included in the preferred range described above may be included. In one example, the proportion of carbon fibers having a length within the preferred range described above is 50% or more of the total carbon fibers based on the number of fibers.

In the resin composition according to one embodiment of the present invention, when the thermoplastic resin is 100 parts by weight, the carbon fiber content is preferably 5 parts by weight to 70 parts by weight, more preferably 10 parts by weight to 45 parts by weight. The reason why this numerical range is suitable is as described in [Means for Solving the Problems].

The carbon fiber preferably has an uneven surface. Since such carbon fibers have a large specific surface area, interaction due to affinity with the conductive filler becomes greater. As a result, the conductive filler tends to aggregate in the vicinity of the carbon fibers.

The carbon fibers may be surface-treated with a sizing agent (such as maleic anhydride-modified polypropylene). By applying such a surface treatment, it is possible to improve the interaction due to the affinity between the carbon fibers and the conductive filler, and to improve the adhesion between the carbon fibers and the thermoplastic resin.

[Conductive filler]
Examples of the conductive filler contained in the resin composition according to one embodiment of the present invention include metal-based fillers, metal oxide-based fillers, carbon-based fillers, metal-coated fillers, and metal oxide-coated fillers. mentioned. Only one type of these conductive fillers may be contained, or two or more types may be contained.

Examples of metallic fillers include metals or alloys such as silver, copper, nickel, aluminum, zinc, stainless steel, and brass. The shape of the metallic filler includes powder, flake, fibrous and the like. Examples of powdered and flake metallic fillers include silver, copper, nickel, aluminum and zinc. Examples of fibrous metallic fillers include copper, stainless steel, and brass.

Examples of metal oxide fillers include aluminum-doped zinc oxide, tin-doped indium oxide, and antimony-doped tin oxide.

Examples of carbon-based fillers include conductive carbon black, metallic carbon nanotubes (both single-walled and multi-walled), and graphene.

Examples of metal-coated fillers include metal, inorganic or organic particles whose surfaces are coated with metal. The metal coating the particle surface can be gold, silver, copper, nickel, tin, and the like.

Examples of metal oxide fillers include metal, inorganic or organic particles whose surfaces are coated with metal oxides. The metal oxide coating the particle surface can be zinc oxide, indium oxide, tin oxide, and the like.

Among the conductive fillers described above, metal-based fillers, metal oxide-based fillers and carbon-based fillers are preferred. The reason why these are preferable is as described in [Means for Solving the Problems].

The thermal conductivity of the conductive filler measured by a laser flash method is preferably 10 W/m·K or more, more preferably 100 W/m·K or more. The reason why this numerical range is preferred is as described in [Means for Solving the Problems].

In the resin composition according to one embodiment of the present invention, when the thermoplastic resin is 100 parts by weight, the content of the conductive filler is preferably 3 parts by weight to 80 parts by weight, more preferably 5 parts by weight to 30 parts by weight. . The reason why this numerical range is suitable is as described in [Means for Solving the Problems].

In the resin composition according to one embodiment of the present invention, in order to localize the conductive filler in the vicinity of the carbon fiber, the percolation threshold (filler particles are connected to each other to express conductivity and thermal conductivity) tends to be lower. That is, the resin composition according to one embodiment of the present invention can contain less filler than a general filler composite resin.

The conductive filler may be surface-treated as long as the effects of the present invention are not impaired. Alternatively, the resin composition may contain a dispersant as long as the effects of the present invention are not impaired. By adopting such a configuration, it is possible to improve the interaction due to the affinity between the carbon fiber and the conductive filler, and to improve the dispersibility of the conductive filler.

Examples of the surface treatment applied to the conductive filler include silane coupling treatment and plating treatment (copper plating, gold plating, etc.).

Examples of dispersants to be contained in the resin composition include styrene/maleic anhydride copolymers, polyacrylates, carboxymethyl cellulose, olefin/maleic anhydride copolymers, polystyrene sulfonates, and acrylamide/acrylic acid copolymers. Alginate, polyvinyl alcohol, polyoxyethylene alkyl ether, polyalkylenepolyamine, polyacrylamide, polyoxypropylene/polyoxyethylene block, polymer starch, polyethyleneimine, aminoalkyl (meth)acrylate copolymer, polyvinylimidazoline, Satokinsan is mentioned.

[Other additives]
The resin composition according to one embodiment of the present invention may contain other additives such as thermoplastic resin, carbon fiber, and conductive filler within a range that does not impair the effects of the present invention. Examples of such additives include dispersants, antioxidants, ultraviolet absorbers, antistatic agents, flame retardants, lubricants, crystal nucleating agents, plasticizers, dyes and pigments.

[Resin composition]
The volume resistivity of the resin composition according to one embodiment of the present invention measured according to JIS K 7194 is preferably 10 ² Ω·cm or less, more preferably 10 ⁰ Ω·cm or less, and 10 ^-1 Ω. · cm or less is more preferable.

The shielding effect of the resin composition according to one embodiment of the present invention measured by the KEC method is preferably 30 dB or more at 1 MHz to 10 MHz, more preferably 30 dB or more at 1 MHz to 1 GHz.

Incidentally, there is a correlation between the volume resistance value and the shielding effect. If the volume resistance value is 10 ² Ω·cm or less, the shielding effect measured by the KEC method tends to be 30 dB or more at 1 MHz to 10 MHz (but less than 30 dB at 100 MHz to 1 GHz). If the volume resistivity is 10 ⁰ Ω·cm or less, the shielding effect measured by the KEC method tends to be 30 dB or more at 1 MHz to 1 GHz.

The thermal conductivity of the resin composition according to one embodiment of the present invention measured by a disk heat flow meter method (ASTM E1530) is preferably 2 W/m·K or more, more preferably 5 W/m·K or more.

The density of the resin composition according to one embodiment of the present invention is preferably less than 2.68 g/cm ³ and more preferably less than 1.90 g/cm ³ .

The reason why the above numerical ranges are preferable is as described in [Means for Solving the Problems].

In addition, the tensile strength of the resin composition according to one embodiment of the present invention, measured based on ISO527-1 and ISO527-2, is preferably 150 MPa or more, more preferably 200 MPa or more. Although the upper limit of the tensile strength is not particularly limited, it can be, for example, 500 MPa or less. A resin composition having a tensile strength of 150 MPa or more can be said to have sufficient strength to replace metal parts (parts made of aluminum die casting (tensile strength: 310 MPa), etc.) with resin parts. That is, if the resin composition has a tensile strength of 150 MPa or more, problems caused by insufficient strength can be suppressed.

The thermoplastic resin according to one embodiment of the present invention can be processed into molded resin parts by known processing techniques. Examples of such processing techniques include injection molding, press molding, blow molding and extrusion.

§3 Production Example The resin composition according to one embodiment of the present invention can be produced under production conditions such that the carbon fibers are isotropically dispersed in a fibrillated state. When the carbon fibers are isotropically dispersed in a fibrillated state, the specific surface area of the carbon fibers increases. Then, interaction based on affinity between the carbon fibers and the conductive filler is likely to occur in the molten thermoplastic resin, and as a result, the conductive filler agglomerates in the vicinity of the carbon fibers. In this way, a resin composition is produced in which the conductive filler is distributed in a mesh-like manner in the thermoplastic resin.

An example of manufacturing conditions for isotropically dispersing the carbon fibers in a fibrillated state includes kneading under shear conditions. For kneading under shear conditions, a high shear processing machine having an internal feedback screw can be suitably used, but is not limited to this. For example, even if an ordinary twin-screw extruder is used, the production conditions can be set such that the carbon fibers are isotropically dispersed in the fibrillated state.

Due to the rotation of the internal feedback screw, the molten resin composition flows while repeating 1 and 2 below.
1. It is extruded to the front of the cylinder.
2. It returns to the rear of the cylinder through the axial passage of the screw.

Such flow of the molten resin composition generates a strong shear flow field and elongational field inside the molten resin composition. The functions of the shear flow field and the elongation field accelerate the disentanglement of the carbon fibers, and further isotropically disperse the disentangled carbon fibers.

In the case of a manufacturing method using a high shear processing machine with an internal feedback screw, the manufacturing conditions (screw rotation speed, residence time, etc.) are determined by (i) the type of thermoplastic resin used, (ii) the blend of carbon fibers It can be appropriately set according to the amount, (iii) the type and blending amount of the conductive filler.

For example, in the resin composition (composed of polyphenylene sulfide resin, carbon fiber, and aluminum filler) described in Example 1 described later, the screw rotation speed can be 1,200 rpm and the residence time can be 60 seconds.

If the screw speed is too high (eg, greater than 1,500 rpm) or the residence time is too long (eg, greater than 180 seconds), shear degradation of the thermoplastic resin and carbon fibers tends to occur. As a result, the mechanical properties of the resin composition tend to deteriorate. Conversely, if the screw rotation speed is too low (e.g., less than 800 rpm) or the residence time is too short (e.g., less than 30 seconds), defibration and dispersion of the carbon fibers and dispersion of the conductive filler will be insufficient. becomes.

In the case of a production method using a twin-screw extruder, the degree of kneading can be adjusted by combining a screw and a suitable kneading disk. The disentangled carbon fibers are isotropically dispersed due to the shearing action between the disc surfaces of the kneading discs and the distributive mixing action caused by the cutting back effect of the discontinuous discs.

The contents described in each of the above items can also be appropriately used in other items. The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Therefore, embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the technical scope of the present invention.

All scientific and patent documents mentioned herein are hereby incorporated by reference.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited only to the following examples.

[Measurement method of physical properties]
(1) Volume resistivity Measured according to JIS K 7194 (resistivity test method for conductive plastics by four-probe method).

(2) Shielding function Shielding performance of 1MHz to 1GHz was evaluated by the KEC method.

(3) Thermal conductivity Measured according to the disk heat flow meter method (ASTM E1530). DTC-300 (TA Instruments) was used as a measuring instrument.

(4) Density Density was calculated based on the dimensional volume and measured weight of the test piece specified in JIS K 7161-2.

[Examples 1 to 5, Comparative Examples 1 and 2]
Aluminum (metallic filler, volume resistivity: 10 ⁻⁴ to 10 ⁻³ Ω·cm, thermal conductivity: about 240 W/m·K) was used as the conductive filler. Changes in the physical properties of the resin composition were examined while changing the content of the filler.

[Example 1]
Polyphenylene sulfide (PPS resin) was used as the thermoplastic resin, PAN carbon fiber was used as the carbon fiber, and aluminum (granular) was used as the conductive filler.

1. Preliminary kneading step 100 parts by weight of PPS resin, 25 parts by weight of PAN carbon fiber, and 10 parts by weight of aluminum were preliminarily kneaded to prepare a masterbatch. A general twin-screw extruder was used for pre-kneading, PPS resin was fed from a hopper, and PAN carbon fiber and aluminum were fed from a side feeder. The kneading temperature was 300° C. and the screw rotation speed was 200 rpm.

2. Main kneading step The pellet-shaped masterbatch obtained in the preliminary kneading step was put into a high-shear processing machine having an internal feedback screw and kneaded. The kneading temperature was 320° C., the screw rotation speed was 1,200 rpm, and the residence time was 60 seconds.

3. Injection Molding Process Pellets of the resin composition obtained in this kneading process were injection molded to prepare a volume resistivity measurement sample conforming to JIS K 7194 and a shield evaluation sample conforming to the KEC method. Table 1 shows the physical properties of the prepared resin composition.

[Examples 2 to 5, Comparative Examples 1 and 2]
A volume resistivity measurement sample conforming to JIS K 7194 and a shield evaluation sample conforming to the KEC method were prepared in the same manner as in Example 1 while changing the amount of aluminum mixed. The manufacturing conditions were appropriately adjusted according to the materials and compounding amounts. Table 1 shows the physical properties of the prepared resin composition.

(result)
All of the resin compositions produced in Examples 1 to 5 had density, volume resistivity, shielding effect and thermal conductivity within preferred ranges. In particular, the resin compositions produced in Examples 1, 2, and 4 have a good balance of these physical properties and can be said to have particularly favorable functions. On the other hand, the resin compositions produced in Comparative Examples 1 and 2 were inferior in volume resistivity, shielding effect and thermal conductivity. In the case of Comparative Example 1, it is considered that the amount of the conductive filler was too small and the formation of the network of the conductive filler was inhibited. In the case of Comparative Example 2, it is considered that the amount of the conductive filler was too large, making kneading difficult, and as a result, the physical properties of the resin composition deteriorated.

[Examples 6 to 10, Comparative Examples 3 and 4]
Conductive carbon black (carbon-based filler, volume resistivity: 10 ⁻¹ to 10 ⁰ Ω·cm, thermal conductivity: about 150 W/m·K) was used as the conductive filler. Changes in the physical properties of the resin composition were examined while changing the content of the filler. The production method of the resin composition was according to Example 1, and was appropriately adjusted according to the materials and compounding amounts. Table 2 shows the physical properties of the prepared resin composition.

(result)
All of the resin compositions produced in Examples 6 to 10 had density, volume resistivity, shielding effect and thermal conductivity within preferred ranges. In particular, the resin compositions produced in Examples 6, 7, and 9 have a good balance of these physical properties and can be said to have particularly favorable functions. On the other hand, the resin compositions produced in Comparative Examples 3 and 4 were inferior in volume resistivity, shielding effect and thermal conductivity. In the case of Comparative Example 3, it is considered that the amount of the conductive filler was too small and the formation of the network of the conductive filler was inhibited. In the case of Comparative Example 4, it is considered that the amount of the conductive filler was too large, making kneading difficult, and as a result, the physical properties of the resin composition deteriorated.

[Examples 11 to 15, Comparative Examples 5 and 6]
A carbon nanotube (carbon-based filler, volume resistivity: 10 ⁻⁴ to 10 ⁻² Ω·cm, thermal conductivity: >2,000 W/m·K) was used as the conductive filler. Changes in the physical properties of the resin composition were examined while changing the content of the filler. The production method of the resin composition was according to Example 1, and was appropriately adjusted according to the materials and compounding amounts. Table 3 shows the physical properties of the prepared resin composition.

(result)
All of the resin compositions produced in Examples 11 to 15 fell within preferred ranges of density, volume resistivity, shielding effect and thermal conductivity. Compared to other fillers, it tends to be superior in volume resistivity and thermal conductivity, and has a low density. Therefore, carbon nanotubes can be said to be a particularly excellent conductive filler in the present invention. On the other hand, the resin compositions produced in Comparative Examples 5 and 6 were inferior in volume resistivity, shielding effect and thermal conductivity. In the case of Comparative Example 5, it is considered that the amount of the conductive filler was too small and the formation of the network of the conductive filler was inhibited. In the case of Comparative Example 6, it is considered that the amount of the conductive filler was too large, making kneading difficult, and as a result, the physical properties of the resin composition also deteriorated.

[Comparative Examples 7 and 8]
In the production method of Example 1, a resin composition was produced without including carbon fiber, and was designated as Comparative Example 7. Further, in the production method of Example 1, a resin composition was produced without including the conductive filler, and was designated as Comparative Example 8. Table 4 shows the physical properties of the prepared resin composition.

(result)
Since the resin composition produced in Comparative Example 7 did not contain carbon fibers serving as a scaffold, no conductive filler network was formed. Therefore, the volume resistivity, shielding effect and heat transfer function were inferior. Since the resin composition produced in Comparative Example 8 did not contain a thermally conductive filler, it exhibited only the shielding effect and thermal conductivity equivalent to those of ordinary CFRTP.

[Examples 16 to 19, Comparative Examples 9 and 10]
Aluminum (metallic filler, volume resistivity: 10 ⁻⁴ to 10 ⁻³ Ω·cm, thermal conductivity: about 240 W/m·K) was used as the conductive filler. Changes in the physical properties of the resin composition were examined while changing the carbon fiber content. The production method of the resin composition was according to Example 1, and was appropriately adjusted according to the materials and compounding amounts. Table 5 shows the physical properties of the prepared resin composition.

(result)
All of the resin compositions produced in Examples 16 to 19 had density, volume resistivity, shielding effect and thermal conductivity within preferred ranges. In particular, it can be said that the resin compositions produced in Examples 16 and 19 have a good balance of these physical properties and have particularly preferable functions. On the other hand, the resin compositions produced in Comparative Examples 9 and 10 were inferior in volume resistivity, shielding effect and thermal conductivity. In the case of Comparative Example 9, the amount of carbon fiber was too small, and it is considered that the formation of the conductive filler network was inhibited. In the case of Comparative Example 10, the amount of carbon fibers was too large, making kneading difficult, and as a result, it is considered that the physical properties of the resin composition deteriorated.

A resin composition according to an embodiment of the present invention can be used, for example, in automobile parts.

REFERENCE SIGNS LIST 1 carbon fiber 2 conductive filler 3 thermoplastic resin 10 resin composition

Claims (7)

A resin composition containing a thermoplastic resin, carbon fibers and a conductive filler,
The carbon fibers are isotropically dispersed in the thermoplastic resin in a defibrated state,
A resin composition in which the conductive filler is aggregated in the vicinity of the carbon fiber,
The thermoplastic resin is one selected from the group consisting of amide-based resins, ester-based resins, ether-based resins, nitrile-based resins, methacrylate-based resins, vinyl-based resins, cellulose-based resins, fluorine-based resins, and imide-based resins. and
The conductive filler is a particulate metallic filler ,
When the thermoplastic resin is 100 parts by weight, the content of the carbon fiber is 5 parts by weight to 30 parts by weight,
The resin composition, wherein the content of the conductive filler is 3 to 45 parts by weight when the thermoplastic resin is 100 parts by weight . 2. The resin composition according to claim 1, which has a volume resistivity of 10< ² > Ω·cm or less as measured according to JIS K 7194. 3. The resin composition according to claim 1, wherein the shielding effect measured by the KEC method is 30 dB or more at 1 MHz to 10 MHz. 4. The resin composition according to any one of claims 1 to 3, which has a thermal conductivity of 2 W/m·K or more as measured by a disk heat flow meter method. The resin composition according to any one of claims 1 to 4, wherein the conductive filler has a thermal conductivity of 10 W/m·K or more as measured by a laser flash method. The resin composition according to any one of claims 1 to 5 , which has a density of less than 2.68 g/cm ³ . A resin molded part comprising the resin composition according to any one of claims 1 to 6 .

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