JP2023139671A - Resin composition and molding - Google Patents

Abstract

To provide a resin composition capable of forming a molding having sufficiently high conductivity.SOLUTION: The resin composition contains: a carbon nanostructure (A) including a plurality of carbon nanotubes having one or more structural forms selected from the group consisting of branching, crosslinking, and sharing of a common wall part; and a polypropylene resin (B) having a melting point (Tm) measured by a differential scanning calorimeter in the range of 135-167°C. The resin composition contains, based on 100 pts.mass of the total of the carbon nanostructure (A) and the polypropylene resin (B), 4.0-13.0 pts.mass of the carbon nanostructure (A) and 87.0-96.0 pts.mass of the polypropylene resin (B).SELECTED DRAWING: None

Description

The present invention relates to a resin composition and a molded article containing the resin composition.

BACKGROUND OF THE INVENTION Conductive materials made of thermoplastic resins imparted with conductivity by adding carbon materials, and molded bodies formed from these conductive materials, are widely used (see, for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 2004-255683 International Publication No. 2018/056215

According to studies by the present inventors, it is difficult to say that molded bodies formed from conventional conductive materials have sufficiently high conductivity. An object of one embodiment of the present invention is to provide a resin composition that can form a molded article having sufficiently high conductivity.

The present inventors conducted studies to solve the above problems. As a result, it was discovered that the above-mentioned problems could be solved by the following configuration example, and the present invention was completed. That is, the present invention relates to, for example, the following [1] to [4].

[1] A carbon nanostructure (A) comprising a plurality of carbon nanotubes having one or more structural forms selected from the group consisting of branching, crosslinking, and sharing a common wall, and measured by a differential scanning calorimeter. A resin composition comprising a polypropylene resin (B) having a melting point (Tm) in the range of 135 to 167°C,
When the total of the carbon nanostructure (A) and the polypropylene resin (B) is 100 parts by mass, the carbon nanostructure (A) is contained in 4.0 to 13.0 parts by mass, and the polypropylene resin A resin composition containing 87.0 to 96.0 parts by mass of (B).
[2] A molded article containing the resin composition according to [1].
[3] The molded article according to [2], which is a molded article for an automobile outer panel.
[4] The molded article according to [2], which is an electrostatic coating component.

According to one aspect of the present invention, it is possible to provide a resin composition that can form a molded article having sufficiently high conductivity. Furthermore, by using the resin composition of the present invention, the coating film thickness is excellent in uniformity, and the molded product obtained has not only high conductivity but also mechanical properties such as flexural modulus and impact strength, and heat resistance. It also has excellent thermal properties.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated.

[Resin composition]
The resin composition of the present invention comprises a carbon nanostructure (A) containing a plurality of carbon nanotubes, and a polypropylene resin (B) having a melting point (Tm) in the range of 135 to 167°C as measured by a differential scanning calorimeter. It is characterized by containing a predetermined amount.

The content of the carbon nanostructure (A) in the resin composition of the present invention is from 4.0 to 4.0 when the total of the carbon nanostructure (A) and the polypropylene resin (B) is 100 parts by mass. The amount is 13.0 parts by weight, preferably 5.0 to 12.0 parts by weight, and more preferably 6.0 to 11.0 parts by weight. When the content of the carbon nanostructure (A) is below the above range, the conductivity tends to increase, that is, the surface electrical resistivity tends to increase. On the other hand, if the content of the carbon nanostructure (A) exceeds the above range, although the electrical conductivity will be low, mechanical properties such as flexural modulus and thermal properties may be inferior, and electrical conductivity and other physical properties may be inferior. It tends to be less balanced.

Further, the content of the polypropylene resin (B) in the resin composition of the present invention is 87.0 to 87.0 parts when the total of the carbon nanostructure (A) and the polypropylene resin (B) is 100 parts by mass. The amount is 96.0 parts by weight, preferably 88.0 to 95.0 parts by weight, and more preferably 89.0 to 94.0 parts by weight. By using a resin composition containing carbon nanostructures (A) and polypropylene resin (B) in the above-mentioned ranges, it has excellent electrical conductivity, that is, low surface electrical resistivity, and has excellent mechanical properties and A molded article with excellent thermal properties can be formed.

<Carbon nanostructure (A)>
The carbon nanostructure (A) in the present invention includes a plurality of carbon nanotubes, and the plurality of carbon nanotubes have one or more structural forms selected from the group consisting of branching, crosslinking, and sharing a common wall. has. By having the above structural form, a plurality of carbon nanotubes can exist in a polymer structure. That is, the carbon nanostructure (A) can be considered to have carbon nanotubes as the basic monomer unit of the polymer structure.

Each carbon nanotube in a plurality of carbon nanotubes need not necessarily have any structural morphology beyond branching, cross-linking, and sharing a common wall, and the plurality of carbon nanotubes as a whole may have one or more of these structural configurations. can have. That is, in some embodiments, at least a portion of the carbon nanotubes are branched, at least a portion of the carbon nanotubes are cross-linked, and at least a portion of the carbon nanotubes share a common wall. Such carbon nanostructures (A) can be easily distinguished from ordinary individual carbon nanotubes by common carbon nanotube analysis techniques such as, for example, scanning electron microscopy (SEM).

The carbon nanotubes in the carbon nanostructure (A) are branched, cross-linked, and share a common wall with each other during the formation of the carbon nanostructure on a growth substrate (e.g., fibrous material). can be formed. Furthermore, when forming carbon nanostructures on a growth substrate, carbon nanotubes can be formed such that they are substantially parallel to each other in the carbon nanostructure, and the carbon nanotubes can be formed such that at least some Aligned parallel to other carbon nanotubes.

The carbon nanostructure (A) exists as a three-dimensional fine structure due to the entanglement and crosslinking of highly oriented carbon nanotubes. The oriented morphology reflects the formation of carbon nanotubes on the growth substrate during rapid carbon nanotube growth conditions (e.g., several microns per second, such as from about 2 to about 10 microns per second), thereby causing substantial separation from the growth substrate. Vertical carbon nanotube growth is produced. Without being bound by any theory or mechanism, it is believed that the fast growth of carbon nanotubes on the growth substrate may contribute, at least in part, to the complex structural morphology of the carbon nanostructures. .

The bulk density of the carbon nanostructure (A) is usually in the range of about 0.003 to 1.2 g/cm ³ . The carbon nanostructures (A) may have a web-like morphology, so that the carbon nanostructures have a low initial bulk density. The as-produced carbon nanostructures can have an initial bulk density ranging from about 0.003 to 0.015 g/cm ³ . Further consolidation and coating to produce carbon nanostructure flakes or similar materials can increase the initial bulk density to a range of about 0.1-0.15 g/cm ³ .

In some embodiments, the carbon nanostructures are optionally further modified (e.g., coating carbon nanotubes, infiltrating the interior of carbon nanostructures, compacting carbon nanostructures, etc.) for use in various applications. By chemically modifying the structure, the bulk density of the carbon nanostructure can be adjusted to an upper limit of about 1 g/cm ³ or about 1.2 g/cm ³ . The bulk density of the carbon nanostructures can also be adjusted by adjusting the growth conditions of the carbon nanostructures, for example by changing the concentration of catalyst particles of transition metal nanoparticles that are placed on the growth substrate to initiate carbon nanotube growth. You can make some adjustments by doing this.

In some embodiments, the carbon nanostructures (A) can be in the form of flake material. Here, flake material refers to discrete particles with finite dimensions. The carbon nanostructures (A) in the form of said flake material may have a "thickness" in the range of about 1 nm to 35 μm, preferably about 1 to 500 nm. Also, the "width" can range from about 1 to 750 microns. Furthermore, the "length" can be any desired length within a wide range of about 1 micron to 10,000 meters. The "length" refers to the dimension extending along the axis of the growth substrate, which is the base on which the carbon nanostructures are formed, and is based on the length of the growth substrate, which is the base on which the carbon nanostructures are initially formed. Only the size is limited.

The carbon nanostructures (A) in the form of flake material comprise a web-like network of carbon nanotubes in the form of a carbon nanotube polymer having a molecular weight in the range of about 15,000 to 1,000,000 g/mol. I can do it. In some embodiments, the upper end of the molecular weight range can be adjusted, such as about 150,000 g/mole, about 200,000 g/mole, or about 500,000 g/mole. The size of the molecular weight can be related to the dimensional size of the carbon nanostructure. In addition, the molecular weight may be related to the diameter of the carbon nanotube serving as the main chain present in the carbon nanostructure and the number of walls of the carbon nanotube. In some embodiments, the carbon nanostructures can have a crosslink density ranging from about 2 to about 80 moles/cm ³ . The crosslinking density is related to the growth density of carbon nanostructures on the surface of the growth substrate and the growth state of the carbon nanostructures.

The carbon nanostructure (A) in the present invention is not particularly limited as long as it has the above-mentioned structural form and the above-mentioned physical properties; Examples include carbon nanostructures disclosed in Japanese Patent No. 535743 and the like. As the carbon nanostructure (A) in the present invention, a commercially available product of the carbon nanostructure or a composite containing the carbon nanostructure (for example, a polymer composite such as a masterbatch) may be used. Examples of commercially available products include carbon nanostructure masterbatches "ATHLOS 200", "ATHLOS 100", and "SR1200 CNS" manufactured by CABOT.

By using the carbon nanostructure (A), the conductivity and strength of the molded body are improved compared to carbon nanotubes (CNT), carbon black (CB), graphene, etc., which are conventionally used as carbon materials. . In addition, since it does not impair its lightness, which is an advantageous characteristic of a carbon material, it is advantageous in applications where lightness and strength are important, such as aircraft applications.

One reason for this is that carbon nanostructures (A) have excellent dispersibility, resulting in favorable carbon nanotube properties (i.e., chemical, mechanical, It is believed that carbon nanostructures can provide superior performance over conventional carbon materials, such as carbon nanotubes, because they can exhibit any combination of physical, electrical, and thermal properties. The excellent dispersibility of carbon nanostructures is thought to be due to the fact that they have a porous macrostructure, which will be described later, and thus have a lower density than individually separated carbon nanotubes.

Carbon nanostructures (A) contain carbon nanotubes that are highly intertwined, branched, cross-linked, and share a common wall, and that the carbon nanotubes and their interconnections make the structure of the mere carbon nanotubes themselves morphology (conventional carbon nanotube forest or unbound carbon nanotubes) with a highly porous macrostructure. The porous macrostructure is maintained robustly by covalent bonds between carbon nanotubes.

Also, using carbon nanostructures (A) minimizes the risk of the strongly bonded carbon nanotubes falling off, thereby reducing the handling problems of individually separated carbon nanotubes and the potential environmental health and safety issues. This is thought to be able to prevent concerns. Additionally, one of the advantages of carbon nanostructures compared to individual carbon nanotubes is that carbon nanostructures may be easier and cheaper to produce than conventional carbon nanotube production techniques. Some conventional carbon nanotube growth processes have carbon conversion efficiencies of up to about 60%. On the other hand, carbon nanostructures can be produced on growth substrates (eg, fibrous materials) with carbon conversion efficiencies of greater than about 85%. Thus, carbon nanostructures make more efficient use of carbon raw materials, with concomitant reductions in production costs.

The content of the carbon nanostructure (A) based on 100% by mass of the resin composition of the present invention is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and still more preferably 3.0% by mass or more. The content is preferably 20.0% by mass or less, more preferably 19.0% by mass or less, even more preferably 18.0% by mass or less. When the content of the carbon nanostructure (A) is within the above range, the resin composition tends to have excellent fluidity during molding.

<Polypropylene resin (B)>
As the polypropylene resin (B) in the present invention, a general polypropylene resin can be used. Examples include homopolypropylene, random polypropylene, and block polypropylene, and among these, block polypropylene is preferred.

Examples of comonomers in random polypropylene and block polypropylene include α-olefins having 2 or more carbon atoms other than propylene, and specifically, ethylene, 1-butene, 2-methyl-1-butene, 3-methyl- 1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, methyl -1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pentene, diethyl-1-butene, 1- Examples include α-olefins having 2 to 20 carbon atoms such as nonene, 1-decene, 1-undecene, and 1-dodecene. Among these, 1-butene, 1-pentene, 1-hexene and 1-octene are preferred.

The melting point (Tm) of the polypropylene resin (B) as measured by a differential scanning calorimeter is in the range of 135 to 167°C, preferably in the range of 150 to 167°C, more preferably in the range of 160 to 167°C. It is preferable that the melting point (Tm) of the polypropylene resin (B) is within the above range from the viewpoint of mechanical properties such as heat resistance and flexural modulus.

The melting point (Tm) of the polypropylene resin (B) is determined by cutting out about 5 mg of a sample using a differential scanning calorimeter (for example, DSC7000X manufactured by Hitachi High-Tech Science Co., Ltd.), placing it in an aluminum pan for measurement, and heating it at 10°C/min. The temperature was raised from 30°C to 230°C at a cooling rate of 230°C, held at 230°C for 5 minutes, then lowered to 30°C at a cooling rate of 10°C/min, held at 30°C for 5 minutes, and then cooled again at 10°C/min. The melting peak that appeared during the second temperature increase when the temperature was raised from 30 °C to 230 °C at a heating rate, held at 230 °C for 5 minutes, and then lowered to 30 °C again at a cooling rate of 100 °C/min. The temperature at the top of the peak is defined as the melting point (Tm) of the polymer. Note that when multiple peaks are detected, the peak detected on the highest temperature side is adopted. Here, the melting point derived from polypropylene resin is detected to be less than 175°C.

A part of the polypropylene resin (B) may be modified with a polar monomer. Specifically, the polypropylene resin (B) may contain acid-modified polypropylene such as maleic anhydride-modified polypropylene and maleic acid-modified polypropylene. For acid modification of acid-modified polypropylene, unsaturated carboxylic acids such as maleic acid, itaconic acid, citraconic acid, fumaric acid, (meth)acrylic acid; maleic anhydride, itaconic anhydride, citraconic anhydride are used as polar monomers. Unsaturated carboxylic acid anhydrides such as can be used. When the polypropylene resin (B) contains acid-modified polypropylene, mechanical properties such as impact strength of the resulting molded article tend to improve.

There are no particular limitations on the method of modification, and any known method may be used. Examples include a method in which polypropylene resin is dissolved in a solvent, a polar monomer and a radical generator are added, and the mixture is heated and stirred, a method in which the above components are fed to an extruder and graft copolymerized, and a solid phase modification method.

The amount of structural units derived from polar monomers in the acid-modified polypropylene (e.g., the amount of grafting) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. , preferably 20% by mass or less, more preferably 15% by mass or less, still more preferably 10% by mass or less. The above amount of structural units can be determined by, for example, infrared absorption spectroscopy.

The content of propylene-derived structural units in the polypropylene resin (B) is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, based on the total amount of all monomer-derived structural units constituting the polymer. It is mol% or more. The content ratio of the structural units can be measured, for example, by ¹³ C-NMR.

The melt flow rate (MFR) of the polypropylene resin (B) at 230°C and a load of 2.16 kg according to JIS K7210 is preferably 0.1 g/10 minutes or more, more preferably 10 g/10 minutes or more. , more preferably 30 g/10 minutes or more, preferably 500 g/10 minutes or less, more preferably 400 g/10 minutes or less, still more preferably 300 g/10 minutes or less.

One or more types of polypropylene resin (B) can be used.
The content ratio of the polypropylene resin (B) to 100% by mass of the resin composition of the present invention is preferably 40.0% by mass or more, preferably 50.0% by mass or more, and even more preferably 60.0% by mass or more, Preferably it is 98.9% by mass or less, more preferably 95.0% by mass or less, still more preferably 90.0% by mass or less. When the content of the polypropylene resin (B) is within the above range, the resin composition tends to have excellent fluidity during molding.

In one embodiment, the content of acid-modified polypropylene in the resin composition is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.2% by mass or more, and preferably is 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less.

<Other ingredients>
The resin composition may further contain resins other than the polypropylene resin (B) and various resin additives.
Examples of additives include impact strength modifiers such as elastomers such as olefin elastomers; low stereoregularity polypropylene that does not fall under polypropylene resin (B); talc, calcium carbonate, metal powder, titanium oxide, zinc oxide Inorganic fillers such as (excluding carbon nanostructures (A)); Coloring agents such as pigments and dyes; Antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, antistatic agents, crystal nucleating agents , dispersants, flame retardants, flame retardant aids, and plasticizers.

The content of the additive in the resin composition is not particularly limited as long as it does not impair the effects of the present invention, but with respect to a total of 100 parts by mass of the carbon nanostructure (A) and the polypropylene resin (B), The amount is preferably 0.01 to 100 parts by weight, more preferably 0.1 to 50 parts by weight, and even more preferably 0.1 to 10 parts by weight.

<Manufacture of resin composition>
The above resin composition can be prepared, for example, by dry blending the carbon nanostructure (A) and the polypropylene resin (B), followed by melt-kneading in a single-screw or twin-screw extruder, extrusion into strands, and granulation into pellets. This can be obtained by Note that components such as the carbon nanostructure (A) and the inorganic filler may be mixed in advance with a resin component such as the polypropylene resin (B) and used in the form of a masterbatch.

[Molded object]
The molded article of this embodiment contains the above resin composition. Specifically, the molding method includes conventionally known polyolefin molding methods, such as extrusion molding, injection molding, film molding, inflation molding, blow molding, extrusion blow molding, injection blow molding, press molding, vacuum molding, and powder molding. Known thermoforming methods such as slush molding, calendar molding, and foam molding can be used. By processing the resin composition, preferably by injection molding, it is possible to obtain the molded article of this embodiment containing the resin composition.

In general, injection molded bodies tend to have lower conductivity (higher surface electrical resistivity) than press molded bodies. With the resin composition of this embodiment, sufficiently high conductivity can be obtained even when injection molding is performed. In this way, the resin composition of the present embodiment can form a molded article having excellent conductivity regardless of the molding method.

The molded object may be a molded object formed from the resin composition, or may be a molded object having a portion, for example, a surface layer, formed from the resin composition.
Furthermore, the molded article of this embodiment also has excellent mechanical properties.

Molded objects are used in a wide range of applications, from household items such as daily necessities and recreational uses to general industrial uses and industrial products. For example, home appliance material parts, communication equipment parts, electrical parts, electronic parts, automobile parts, other vehicle parts, ships, aircraft materials, mechanical mechanism parts, building materials related parts, civil engineering parts, agricultural materials, power tool parts, food containers. , films, sheets, and fibers.

Automotive parts include, for example, front doors, back doors, sliding doors, front end modules, door modules, fenders, foil caps, gasoline tanks, seats (filling, outer material, etc.), belts, ceiling coverings, convertible tops, armrests, and door trims. , rear package tray, carpet, mat, sun visor, foil cover, tire, mattress cover, air bag, connector, insulation material, hanging handle, hanging strap, wire covering material, electrical insulation material, paint, coating material, lining materials, flooring materials, corner walls, deck panels, covers, plywood, ceiling boards, partition boards, side walls, carpets, wallpaper, wall covering materials, exterior materials, interior materials, roofing materials, soundproofing boards, heat insulation boards, window materials. Can be mentioned.

Examples of home appliance material parts, communication equipment parts, electrical parts, and electronic parts include printers, personal computers, word processors, keyboards, PDAs (small information terminals), headphone stereos, mobile phones, telephones, facsimile machines, copying machines, and ECRs (electronic Office/OA equipment such as cash registers, calculators, electronic notebooks, electronic dictionaries, cards, holders, and stationery; Home appliances such as washing machines, refrigerators, vacuum cleaners, microwave ovens, lighting equipment, game consoles, irons, and kotatsu. ; AV equipment such as TVs, VTRs, video cameras, radio cassette players, tape recorders, mini discs, CD players, speakers, liquid crystal displays; connectors, relays, capacitors, switches, printed circuit boards, coil bobbins, semiconductor sealing materials, electric wires, cables, Examples include parts used in transformers, deflection yokes, distribution boards, clocks, and robot materials.

Examples of daily necessities include clothing, curtains, sheets, plywood, synthetic fiber boards, carpets, doormats, sheets, buckets, hoses, containers, glasses, bags, cases, goggles, skis, rackets, tents, bicycles, musical instruments, etc. Examples include daily life and sporting goods.

As the molded article of this embodiment, an injection molded article is preferable.
An automobile outer panel will be described below as one of the preferred uses of the above-mentioned molded body. The molded product, particularly the injection molded product, can be suitably used as a molded product for an automobile outer panel. Examples of the final product include an automobile having the above-mentioned molded body, particularly an injection molded body, as an outer panel of the vehicle.

Examples of automobile outer panels include bumpers, fenders, side doors, engine hoods, back doors, roof panels, fuel lid covers, trunks, and side skirts, with bumpers and fenders being preferred.

Hereinafter, a method for manufacturing an automobile having the above-mentioned molded body, particularly an injection molded body, as an outer panel of the vehicle will be explained. Surface painting of automobile exterior panels is usually automated by electrostatic painting. In the above painting, conventional methods include painting the resin outer panel and the car body separately (offline painting), and attaching the resin outer plate to the car body and painting the resin outer plate and the car body together (online painting). )It has been known. Online painting is desirable from the viewpoints of simplifying the automobile production process, shortening production time, and reducing paint loss during the painting process.

The above manufacturing method includes a step (1) of attaching the molded article of the present embodiment, particularly an injection molded article, to an automobile body, and a step (2) of online painting the automobile body to which the molded article is attached. The step (3) of drying the automobile body after the step (2) is performed in this order.

In the step (1), the molded body is attached to an automobile body, and in the step (2), the molded body and the automobile body are integrally painted (on-line painting). Such a method is more preferable than painting the molded body and the automobile body separately from the viewpoint of improving automobile productivity and reducing paint loss.

In the step (2) and the step (3), for example, an intermediate coat and a top coat (e.g., base and clear) may be applied in step (2), and drying may be performed in step (3), and step (2) And step (3) may be repeated to perform intermediate coating and drying, top coating and drying.

There are no particular limitations on the method of applying the intermediate coating and top coating, and for example, known coating methods such as spray coating and electrostatic coating can be used. For on-line painting that integrally paints the molded body and the automobile body, electrostatic painting is preferred.

In this embodiment, even when electrostatically painting is performed using an intermediate coating and/or top coating in step (2), the surface of the molded product having the surface layer formed from the resin composition of this embodiment does not have conductivity. Therefore, there is no need to apply a primer coating to provide the conductivity required for electrostatic coating.

The molded article of this embodiment, especially the injection molded article, can also be suitably used as a part for electrostatic coating. Electrostatic coating parts are parts suitable for surface painting using the electrostatic coating method, and can be used not only for the above-mentioned automobile exterior panels, but also for various applications such as the above-mentioned home appliance material parts, communication equipment parts, electrical parts, etc. Included in parts used in As an example of the coating method when the molded article of this embodiment is used as a part for electrostatic coating, a coating method (for example, online coating or offline coating) when used as an outer panel of an automobile is mentioned. An appropriate known coating method may be selected depending on the various uses of the parts in the various final products as described above.

Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to these Examples. In the following description of Examples, etc., "parts" indicate "parts by mass" unless otherwise specified.

[Measurement of melting point (Tm)]
Using a differential scanning calorimeter (DSC) measuring device DSC7000X manufactured by Hitachi High-Tech Science, cut out approximately 5 mg of a sample from a 1 mm thick flat test piece (see below), packed it in an aluminum pan for measurement, and heated at a heating rate of 10°C/min. The temperature was raised from 30°C to 230°C, held at 230°C for 5 minutes, then lowered to 30°C at a cooling rate of 10°C/min, held at 30°C for 5 minutes, and then heated again at a heating rate of 10°C/min. The temperature was raised from 30°C to 230°C, held at 230°C for 5 minutes, and then lowered to 30°C again at a cooling rate of 100°C/min. The melting peak that appeared during the second temperature rise was defined as the melting point (Tm).

[Method for producing resin composition and test piece for measuring physical properties]
The dry blend described in the Examples or Comparative Examples was put into the hopper part of KZW15 manufactured by Technovel Co., Ltd., and melt-kneaded at 230° C. to produce resin composition pellets.
Thereafter, the resin composition pellets were put into the hopper part of Toshiba 75 ton injection molding machine manufactured by Toshiba Machine Co., Ltd., melted at 230 ° C., and injection molded into a mold at 40 ° C. at an injection pressure of 60 MPa and a holding pressure of 20 MPa. A flat test piece of 130 mm x 120 mm x 1 mm thickness, a heat distortion temperature (HDT) measurement test piece based on ASTM D648, a Charpy impact test piece based on JIS K7111, and a bending test piece based on ASTM D790 were prepared. did.

[Measurement of surface electrical resistivity]
The surface electrical resistivity of the test piece was determined as follows.
The above 1 mm thick flat test piece was measured using the double ring method using a digital ultra-high resistance/micro ammeter model 8340A manufactured by ADC Co., Ltd. at a room temperature of 23°C, a humidity of 50%, an applied voltage of 10 V, and an application time of 60 Measured under conditions of 2 seconds.

In the above measurement, for the test pieces whose resistance was less than 1.0×10 ⁶ Ω, the surface electrical resistivity was determined as follows. The above 1 mm thick flat test piece was tested using the 4-probe method at a room temperature of 23°C and a humidity of 50% using a resistivity meter Lorester GX MCP-T700 manufactured by Nitto Seiko Analytech Co., Ltd. and an ASP type probe. Measured according to JISK7194;1994.

[Measurement of flexural modulus]
The bending elastic modulus was measured for the above bending test piece using a 5-point bending tester for 3-point bending manufactured by Shimadzu Corporation at a test speed of 1.3 mm/min at 23°C in accordance with ASTM D790. went.

[Measurement of heat distortion temperature (HDT)]
HDT measurement was performed on the above HDT measurement test piece using an automatic HDT testing machine manufactured by Toyo Seiki Seisakusho Co., Ltd. in accordance with ASTM D648 (0.45 MPa load).

[Charpy impact test]
The Charpy impact test was performed on the Charpy impact test piece described above at 23° C. using a C1-4-01 tester manufactured by Tokyo Test Instruments in accordance with JIS K7111.

[Example 1]
92.9% by mass of polypropylene J707G manufactured by Prime Polymer (melting point: 160°C, MFR at 230°C under 2.16 kg load: 30g/10min) and carbon structure (CNS) masterbatch ATHLOS 200 (carbon nano structure (93% by mass of carbon nanostructure: CNS + 7% by mass of polyethylene glycol) and 6.5% by mass of low stereoregular polypropylene Elmodu (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd. as an additive. 6% by mass were dry blended. The ratio of each component is shown in Table 1. Next, resin composition pellets and test pieces for measuring physical properties were produced by the method described above. Surface electrical resistivity measurements, heat distortion temperature (HDT) measurements, Charpy impact tests, and flexural modulus measurements were performed using each of the above test pieces. The results are shown in Table 1.

[Examples 2 and 3, Comparative Examples 1 and 2]
Resin composition pellets and test pieces for measuring physical properties were prepared in the same manner as in Example 1, except that the raw materials were used in the proportions shown in Table 1. Surface electrical resistivity measurements, heat distortion temperature (HDT) measurements, Charpy impact tests, and flexural modulus measurements were performed using each of the above test pieces. The results are shown in Table 1.

[Comparative example 3]
83.5% by mass of polypropylene J707G manufactured by Prime Polymer Co., Ltd. and 15.0% of carbon nanotube (CNT) masterbatch P2003 (20% by mass of carbon nanotubes + 80% by mass of polypropylene corresponding to polypropylene resin (B)) manufactured by Toyo Color Co., Ltd. % by mass and 1.5% by mass of low stereoregular polypropylene Elmodu (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd. as an additive were dry blended. The ratio of each component is shown in Table 1. Next, resin composition pellets and test pieces for measuring physical properties were produced by the method described above. Surface electrical resistivity measurements, heat distortion temperature (HDT) measurements, Charpy impact tests, and flexural modulus measurements were performed using each of the above test pieces. The results are shown in Table 1.

[Comparative Examples 4 to 6]
Resin composition pellets and test pieces for measuring physical properties were produced in the same manner as in Comparative Example 3, except that the raw materials were used in the proportions shown in Table 1. Surface electrical resistivity measurements, heat distortion temperature (HDT) measurements, Charpy impact tests, and flexural modulus measurements were performed using each of the above test pieces. The results are shown in Table 1.

[Comparative Example 7]
96.8% by mass of polypropylene J707G manufactured by Prime Polymer Co., Ltd. and carbon black (CB) masterbatch P-5050 manufactured by DIC Corporation (25% by mass of carbon black + 75% by mass of polypropylene corresponding to polypropylene resin (B)). 0% by mass and 1.2% by mass of low stereoregularity polypropylene Elmodu (registered trademark) S901 manufactured by Idemitsu Kosan Co., Ltd. as an additive were dry blended. The ratio of each component is shown in Table 1. Next, resin composition pellets and test pieces for measuring physical properties were produced by the method described above. Surface electrical resistivity measurements were carried out using each of the above test pieces. The results are shown in Table 1.
are shown in Table 1.

[Comparative Examples 8 and 9]
Resin composition pellets and test pieces for measuring physical properties were produced in the same manner as in Comparative Example 7, except that the raw materials were used in the proportions shown in Table 1. Surface electrical resistivity measurements were carried out using each of the above test pieces. The results are shown in Table 1.

[Comparative Example 10]
A test piece for measuring physical properties was prepared using 100% by mass of polypropylene J707G manufactured by Prime Polymer. Surface electrical resistivity measurements, heat distortion temperature (HDT) measurements, Charpy impact tests, and flexural modulus measurements were performed using each of the above test pieces. The results are shown in Table 1.

Molded objects obtained from resin compositions containing carbon nanotubes (CNTs) or carbon black (CB) as carbon materials (Comparative Examples 3 to 9) are obtained from resin compositions containing carbon nanostructures (CNS) (A). Compared to the obtained molded bodies (Examples 1 to 3), the conductivity was lower, that is, the surface electrical resistivity was higher. Furthermore, they tend to be inferior in terms of mechanical properties such as flexural modulus. Furthermore, even when carbon nanostructures (A) are used, if the content of carbon nanostructures (A) and polypropylene resin (B) is within the range specified in the present invention, the electrical conductivity will be low. , both mechanical properties and thermal properties are excellent (Examples 1 to 3), but outside the above range, the balance of electrical conductivity, mechanical properties, and thermal properties is poor (Comparative Examples 1 and 2).

Claims (4)

A carbon nanostructure (A) comprising a plurality of carbon nanotubes having one or more structural forms selected from the group consisting of branching, crosslinking, and sharing a common wall, and a melting point measured by a differential scanning calorimeter. A resin composition comprising a polypropylene resin (B) having (Tm) in the range of 135 to 167°C,
When the total of the carbon nanostructure (A) and the polypropylene resin (B) is 100 parts by mass, the carbon nanostructure (A) is contained in 4.0 to 13.0 parts by mass, and the polypropylene resin A resin composition containing 87.0 to 96.0 parts by mass of (B). A molded article comprising the resin composition according to claim 1. The molded article according to claim 2, which is a molded article for an automobile outer panel. The molded article according to claim 2, which is a component for electrostatic coating.