CN113817264A - Resin molded article - Google Patents

Abstract

The invention provides a resin molded body with excellent heat dissipation and impact resistance. The resin molded body has thermal conductivity and has a main surface, the resin molded body comprises a thermoplastic resin and graphite particles, the volume average particle diameter of the graphite particles is more than 0.1 [ mu ] m and less than 40 [ mu ] m, the content of the graphite particles is more than 10 parts by weight and less than 200 parts by weight relative to 100 parts by weight of the thermoplastic resin, and when an arbitrary direction is an x direction, a direction perpendicular to the x direction is a y direction, and a thickness direction of the resin molded body is a z direction on the main surface, the thermal conductivity [ lambda ] x in the x direction, the thermal conductivity [ lambda ] y in the y direction, and the thermal conductivity [ lambda ] z in the z direction satisfy: min (lambda x, lambda y)/lambda z is more than or equal to 3 lambda y.

Description

Resin molded article

The application is a divisional application of an invention patent application with the Chinese application number of 201780017472.X, the application date of 2017, 4 months and 4 days, and the name of the invention is 'resin forming body'.

Technical Field

The present invention relates to a thermally conductive resin molded body.

Background

Conventionally, it is known that a metal plate, a thermally conductive resin molded body, or the like is used for a housing of a communication device used indoors and outdoors, and an electronic device such as a security camera or a standard watch.

Patent document 1 discloses a resin molded article made of a thermoplastic resin containing pitch-based carbon fibers. In patent document 1, the pitch-based fibers of the resin molded article are arranged in the MD direction (the resin flow direction during injection molding). It is described that the ratio (λ 2/λ 1) of the thermal conductivity λ 1 in the thickness direction to the thermal conductivity λ 2 in the MD direction is 10 or more.

Patent document 2 discloses a heat dissipation base plate which is a molded body of a thermally conductive resin composition. Patent document 2 describes a thermally conductive resin composition containing: any one or more of graphite, magnesium oxide, and boron nitride. Further, the amount of the heat conductive filler is 10 to 1000 parts by mass per 100 parts by mass of the resin.

Patent document 3 discloses a heat radiating member which is a molded article (resin molded article) of a thermally conductive resin composition. Patent document 3 describes: the thermally conductive resin composition contains a thermoplastic resin and flake graphite. The thermoplastic resin is contained at a ratio of 30 to 90 mass%. The flake graphite is contained at a ratio of 10 to 70 mass%. Patent document 3 describes that the volume average particle diameter of the flaky graphite is 40 to 700 μm, and the aspect ratio is 21 or more.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-120358

Patent document 2: japanese laid-open patent publication No. 2008-31359

Patent document 3: international patent No. 2015/06566

Summary of The Invention

Technical problem to be solved by the invention

At present, electronic devices such as wireless or wired communication devices, security cameras, and standard watches are installed indoors and outdoors; or a display device such as an FPD or a car navigation system; and an ECU case, the entire or a part of which is formed of a die cast product or a metal press-formed product made of metal. A metal die cast product or a metal press-formed product is formed so as to cover the electronic parts inside. In recent years, studies have been made to replace the metal die cast product or the metal press-worked product described above with a resin.

However, when the resin molded bodies of patent documents 1 to 3 are used for the housing, the products such as electronic devices are damaged or strained when dropped. That is, the resin molded articles of patent documents 1 to 3 have insufficient impact resistance.

The purpose of the present invention is to provide a resin molded body having excellent heat dissipation properties and impact resistance.

Means for solving the problems

The resin molded body according to the present invention has thermal conductivity, and is a resin molded body having a main surface, the resin molded body containing a thermoplastic resin and graphite particles, the graphite particles having a volume average particle diameter of 0.1 μm or more and less than 40 μm, the content of the graphite particles being 10 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the thermoplastic resin, and when an arbitrary direction is an x direction, a direction perpendicular to the x direction is a y direction, and a thickness direction of the resin molded body is a z direction on the main surface, a thermal conductivity λ x in the x direction, a thermal conductivity λ y in the y direction, and a thermal conductivity λ z in the z direction satisfy: min (lambda x, lambda y)/lambda z is not less than 3.

In a specific aspect of the resin molded body according to the present invention, the main surface is a flat surface or a curved surface.

In another specific aspect of the resin molded article according to the present invention, the λ x, the λ y, and the λ z satisfy min (λ x, λ y)/λ z ≧ 11.

In another specific aspect of the resin molded article according to the present invention, the specific gravity is 1.0 or more and less than 1.4.

In still another specific aspect of the resin molded article according to the present invention, λ x and λ y satisfy a condition that λ x/λ y is 0.5 or more and 2 or less.

In still another specific aspect of the resin molded article according to the present invention, the λ z satisfies λ z < 2(W/m · k).

In still another specific aspect of the resin molded article according to the present invention, the graphite particles are plate-shaped.

In still another specific aspect of the resin molded product according to the present invention, the graphite particles have 2 or more different particle size peaks in a range where a volume average particle size in a volume average particle size distribution of the graphite particles is 150 μm or less.

In still another specific aspect of the resin molded article according to the present invention, in a range where a volume average particle diameter in a volume average particle diameter distribution of the graphite particles is 150 μm or less, when a volume average particle diameter of the graphite particles constituting a minimum particle diameter peak is d1 and a volume average particle diameter of the graphite particles constituting a maximum particle diameter peak is d2, 0.1. ltoreq. d1/d 2. ltoreq.0.6 is satisfied.

In still another specific aspect of the resin molded article according to the present invention, in a range where the volume average particle diameter in the volume average particle diameter distribution of the graphite particles is 150 μm or less, when the peak frequency of the minimum particle diameter peak is p1 (%), and the peak frequency of the maximum particle diameter peak is p2 (%), 0.1. ltoreq. p1/p 2. ltoreq.0.9 is satisfied.

In still another specific aspect of the resin molded article according to the present invention, the resin molded article further contains a fibrous filler.

In still another specific aspect of the resin molded article according to the present invention, the content of the fibrous filler is 1 part by weight or more and 200 parts by weight or less based on 100 parts by weight of the thermoplastic resin.

In still another specific aspect of the resin molded article according to the present invention, the thermoplastic resin contains an olefin-based resin.

In a further related specific aspect of the resin molded article according to the present invention, the olefin-based resin contains an ethylene component, and the content of the ethylene component is 5 to 40% by mass.

In still another specific aspect of the resin molded article according to the present invention, a temperature at which the resin molded article exhibits a maximum value of loss tangent, which is obtained by dynamic viscoelasticity measurement under conditions of a frequency of 1Hz and a strain of 0.3%, is 20 ℃ or lower.

In still another specific aspect of the resin molded body according to the present invention, the resin molded body has a shape of a heat dissipation chassis, a heat dissipation casing, or a heat sink.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a resin molded body having excellent heat dissipation performance and impact resistance can be provided.

Brief description of the drawings

FIG. 1(a) is a schematic plan view of a resin molded body obtained in example, and FIG. 1(b) is a schematic sectional view taken along line A-A.

FIG. 2 is a schematic configuration diagram of a housing obtained in the example.

Fig. 3 is a graph showing a volume particle size distribution of graphite particles as an example.

Fig. 4 is a schematic view of a heat sink chassis.

Fig. 5 is a schematic view of the heat dissipation housing.

Fig. 6 is a schematic view of the shape of the heat sink.

Fig. 7 is a graph showing the volume particle diameter of the graphite particles of example 14.

Description of the symbols

1 … resin molded article

2 … clip

3 … basket body

Method for carrying out the invention

The present invention will be described in detail below.

The resin molded article of the present invention is a thermally conductive resin molded article having thermal conductivity and a main surface. The resin molded article of the present invention contains a thermoplastic resin and graphite particles. The volume average particle diameter (hereinafter, also referred to as an average particle diameter) of the graphite particles is 0.1 μm or more and less than 40 μm. The content of the graphite particles is 10 parts by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the thermoplastic resin.

As described above, the resin molded article of the present invention contains graphite particles having an average particle diameter in a specific range in a specific ratio, and therefore, is excellent in both heat dissipation and impact resistance. The reason is as follows.

When the resin molded article according to the present invention is impacted, interfacial separation occurs between the graphite particles and the resin, and the resin molded article is broken. Here, even when minute interfacial exfoliation occurs, at most one graphite particle is considered to promote exfoliation, but the smaller the area of one graphite particle, the smaller the area of exfoliation. In addition, as for the content, the smaller the content of the graphite particles, the smaller the interfacial area between the graphite particles and the resin, which is the origin of fracture. In the present invention, since the resin molded article contains the graphite particles having an average particle diameter smaller than the upper limit in an amount of not more than the upper limit, impact resistance can be improved.

In the resin molded article of the present invention, the graphite particles are contained in an amount of not less than the lower limit, and therefore, the resin molded article has excellent heat dissipation performance, and the average particle diameter of the graphite particles is not less than the lower limit.

In particular, the resin molded article of the present invention has a thermal conductivity in the x direction of λ x, a thermal conductivity in the y direction of λ y, and a thermal conductivity in the z direction of λ z, and satisfies min (λ x, λ y)/λ z ≧ 3.

The x-direction is an arbitrary direction along the main surface. The y-direction is a direction along the main surface and perpendicular to the x-direction. The z direction is a thickness direction of the resin molded body. The thickness direction of the resin molded body is a direction perpendicular to the main surface. Therefore, the z direction is a direction perpendicular to the x direction and the y direction. The main surface may be a flat surface or a curved surface. In the present specification, the main surface refers to a surface having the largest area among a plurality of surfaces on the outer surface of the resin molded body, and also refers to a continuous surface.

The thermal conductivities in the x direction, the y direction, and the z direction can be calculated by the above equation (1).

Thermal conductivity (W/(m · k)) ═ thermal diffusivity × specific gravity × specific heat … (1)

In the formula (1), the thermal diffusivity in each of the x, y and z directions may be, for example, a product name manufactured by Bethel corporation: TA 33.

The min (λ x, λ y) is a value at which the thermal conductivity is small, out of λ x and λ y. Therefore, min (λ x, λ y)/λ z ≧ 3 means that the ratio of the thermal conductivity to λ z, which is small, of λ x and λ y is 3 or more.

In the resin molded article of the present invention, since min (λ x, λ y)/λ z is 3 or more, the thermal conductivity in the surface direction is relatively high as compared with the thermal conductivity in the thickness direction. Therefore, the resin molded article of the present invention has excellent heat dissipation properties in the planar direction.

The resin molded article of the present invention is excellent in both heat dissipation and impact resistance, and therefore can be suitably used for housings of electronic devices such as communication devices, security cameras, and reference watches indoors and outdoors. In particular, since the heat dissipation property in the plane direction is excellent, it is possible to prevent hot dipping of sunlight or the like from penetrating into the communication device and the electronic device. Specifically, for example, heat of a portion irradiated with direct sunlight may be radiated on the surface of the shadow portion. In addition, the heat of the heat generating components inside the enclosure is radiated in the surface direction, thereby suppressing a local increase in the temperature of the communication device or the electronic device. Further, if a part of the housing has a shape of a heat radiation fan, the heat radiation effect can be exhibited. For example, when the temperature of a CPU or the like is too high, the operation capability is lowered, and heat near the CPU can be radiated in a wide range.

In the present invention, from the viewpoint of further improving the thermal conductivity in the plane direction, min (λ x, λ y)/λ z is preferably 5 or more, min (λ x, λ y)/λ z is more preferably 8 or more, min (λ x, λ y)/λ z is more preferably 11 or more, min (λ x, λ y)/λ z is more preferably 13 or more, min (λ x, λ y)/λ z is particularly preferably 15 or more, and min (λ x, λ y)/λ z is most preferably 17 or more. The higher the upper limit of min (. lamda.x,. lamda.y)/λ z is, the better, but the material performance is preferably about 20. Although the length and width of the graphite particles contribute, when the thickness of the graphite particles is small, the graphite particles themselves are aggregated in the thermoplastic resin, and thus sufficient thermal conductivity characteristics cannot be obtained.

In the case of min (λ x, λ y)/λ z, for example, it can be increased by the following suitable method: increasing the volume average particle size of the graphite particles; or increasing the addition amount of graphite particles; or the graphite particles are shaped into a plate; or improving the orientation of the plate-shaped graphite particles along the x direction and the y direction; or the graphite particles are flaked to increase the surface area and the contact points between the particles; or using a plurality of graphite particles having different volume average particle diameters.

In the present invention, λ x/λ y corresponding to λ x and λ y is preferably 0.5 or more and 2 or less. In this case, in the plane direction, more uniform heat dissipation can be achieved. In particular, since the portion irradiated with direct sunlight (high temperature portion) and the shaded portion (low temperature portion) are not always the same plane, it is preferable that the heat can be radiated in any horizontal direction. Therefore, λ x/λ y is more preferably 0.7 or more, further preferably 0.9 or more, still more preferably 1.6 or less, and still more preferably 1.2 or less.

In the case of the λ x and the λ y, max (λ x, λ y) ≧ 1W/(m · k) is preferably satisfied. The max (λ x, λ y) is a value at which the thermal conductivity is high, out of λ x and λ y. Therefore, max (λ x, λ y) ≧ 1W/(m · k) means that the thermal conductivity of λ x and λ y, which is high, is 1W/(m · k) or more. When max (λ x, λ y) is within the above range, heat dissipation can be further improved. From the viewpoint of further improving the heat dissipation performance, it is more preferable that λ x and λ y be max (λ x, λ y) ≥ 3W/(m · k), and it is further preferable that max (λ x, λ y) ≥ 10W/(m · k). The higher the upper limit of max (λ x, λ y) is, the better, but it is desirable to set the upper limit to about 20 in terms of material properties. In the present invention, both λ x and λ y are preferably 1W/(m · k), more preferably 3W/(m · k) or more, and still more preferably 10W/(m · k) or more.

In the present invention, λ z preferably satisfies λ z < 2 (W/m.k), more preferably λ z < 1 (W/m.k). In this case, the heat dissipation performance of the resin molded body can be further improved.

In the present invention, the impact resistance can be evaluated by subjecting a notched test piece to a Charpy impact resistance test in an environment of 23 ℃ in accordance with JIS K7111.

Further, the resin molded article of the present invention is preferably a molded article of a resin composition containing a thermoplastic resin and first flaky graphite particles. The resin composition of the resin molded article of the present invention can be molded by, for example, a method such as press molding, extrusion lamination, and injection molding. Among the molding methods, injection molding is preferable, which can uniformly orient graphite particles. The resin molded article of the present invention may be a molded article of a resin composition containing a thermoplastic resin and graphite particles other than the first flaky graphite particles. For example, the molded article may be a molded article of a resin composition containing a thermoplastic resin and plate-like graphite particles.

The graphite particles contained in the resin molded product of the present invention are preferably plate-shaped. When the graphite particles are plate-shaped, the heat dissipation performance in the plane direction can be further improved. The shape of the graphite particles contained in the resin molded product of the present invention can be measured, for example, by a Scanning Electron Microscope (SEM). From the viewpoint of easier observation, it is desirable that a test piece cut out from a resin molded body is observed with a Scanning Electron Microscope (SEM) while scattering resin by heating at 600 ℃.

The average radial thickness of the graphite particles is not particularly limited, but is preferably 0.1 μm or more and less than 10 μm. When the average radial thickness of the graphite particles is not less than the lower limit, the heat dissipation properties can be further improved. On the other hand, when the average radial thickness of the graphite particles is less than the upper limit, the impact resistance can be further improved.

The average radial thickness of the graphite particles can be determined, for example, using a Scanning Electron Microscope (SEM). From the viewpoint of further easy observation, it is desirable that a test piece cut out from a resin molded article is observed with a Scanning Electron Microscope (SEM) while scattering the resin by heating at 600 ℃. The test piece may be cut along the main surface of the resin molded body or may be cut along a direction perpendicular to the main surface of the resin molded body as long as the resin is scattered and the thickness of the graphite particles can be measured.

In the present invention, the volume average particle diameter is defined as a particle diameter in accordance with JIS Z8825: 2013, and a value calculated from a volume standard distribution by a laser diffraction method using a laser diffraction/scattering particle size distribution measuring apparatus.

In the present invention, when the volume average particle size distribution of the graphite particles contained in the resin molded body is measured, it is preferable that the volume average particle size is 150 μm or less and that the graphite particles have 2 or more peaks having different particle sizes. When there are 2 or more peaks having different particle diameters, both the heat dissipation property and the impact resistance can be further improved. In fig. 3, as an example, a volume particle size distribution of graphite particles is shown, and in this case, it is known that 2 different particle size peaks shown by an arrow A, B in fig. 3 are present.

In the present invention, when the graphite particles having 2 or more different particle diameters as described above have a volume average particle diameter of d1 for the graphite particles constituting the minimum particle diameter peak and d2 for the graphite particles constituting the maximum particle diameter peak, it is preferable that d1/d2 is 0.1. ltoreq.0.6. When d1/d2 is within the above range, heat dissipation and impact resistance can be further improved. From the viewpoint of further improving heat dissipation and heat resistance, d1/d2 is preferably in the range of 0.1. ltoreq. d1/d 2. ltoreq.0.5, and more preferably in the range of 0.2. ltoreq. d1/d 2. ltoreq.0.5. In fig. 3, for example, the peak indicated by the arrow a is a minimum particle size peak, and the peak indicated by the arrow B is a maximum particle size peak.

In the present invention, when there are 2 or more different particle size peaks as described above, the peak frequency of the minimum particle size peak is p1 (%), and the peak frequency of the maximum particle size peak is p2 (%), it is preferable that 0.1. ltoreq. p1/p 2. ltoreq.0.9 is satisfied. When p1/p2 is within the above range, both heat dissipation and impact resistance can be further improved. From the viewpoint of further improving heat dissipation and heat resistance, p1/p2 is preferably in the range of 0.3. ltoreq. p1/p 2. ltoreq.0.8, and more preferably in the range of 0.4. ltoreq. p1/p 2. ltoreq.0.7.

The resin molded article of the present invention preferably has a temperature at which the loss tangent exhibits a maximum value, as measured by dynamic viscoelasticity measurement, of 20 ℃ or less at a frequency of 1Hz and a strain of 0.3%. When the temperature at which the loss tangent of the resin molded article exhibits a maximum value is 20 ℃ or less, the falling ball impact strength of the resin molded article can be further improved. The maximum value of the loss tangent can be determined by the same method as that of the maximum value of the loss tangent of the first resin described later.

The resin molded body of the present invention may have a shape of a heat dissipation chassis, a heat dissipation casing, or a heat sink.

Fig. 4 is a schematic view of a heat sink chassis. When the resin molded body is a heat sink, a portion indicated by an arrow C in fig. 4 is a main surface.

Fig. 5 is a schematic view of the heat dissipation casing. When the resin molded body is a heat dissipation case, a portion indicated by an arrow D in fig. 5 is a main surface. As shown in fig. 4 and 5, the principal surface may have irregularities.

Fig. 6 is a schematic view of the shape of the heat sink. When the resin molded body is in the shape of a heat sink, a portion indicated by an arrow E in fig. 6 is a main surface. In this case, the main surface indicated by the arrow E and a plurality of surfaces connected with each other with a smaller surface interposed therebetween and having substantially the same size are also used as the main surfaces. As described above, there may be a plurality of main faces.

Next, the materials constituting the resin composition and the resin molded article will be described in detail.

(thermoplastic resin)

The thermoplastic resin is not particularly limited, and a known thermoplastic resin can be used. Specific examples of the thermoplastic resin include: polyolefin, polystyrene, polyacrylate, polymethacrylate, polyacrylonitrile, polyester, polyamide, polyurethane, polyethersulfone, polyetherketone, polyimide, polydimethylsiloxane, polycarbonate, or a copolymer of at least any two of these, and the like. The thermoplastic resin may be used alone or in combination of two or more.

The thermoplastic resin is preferably a resin having a high elastic modulus. Polyolefins are preferred because they are inexpensive and can be easily molded by heating.

The polyolefin is not particularly limited, and known polyolefins can be used. As a specific example of the polyolefin, at least one selected from the following may be used: polyolefin resins such as polyethylene, ethylene- α -olefin copolymers, ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylate copolymers, and ethylene-vinyl acetate copolymers as ethylene homopolymers; polypropylene resins such as polypropylene and propylene- α -olefin copolymers as propylene homopolymers; butene homopolymer is a homopolymer or copolymer of a conjugated diene such as polybutene, butadiene or isoprene. From the viewpoint of further improving heat resistance and elastic modulus, polypropylene is preferable as the polyolefin.

The polyolefin (olefin-based resin) preferably contains an ethylene component. The content of the ethylene component is preferably 5 to 40% by mass. When the content of the ethylene component is within the above range, the impact resistance of the resin molded article can be further improved, and the heat resistance can be further improved.

The thermoplastic resin preferably contains a first resin comprising an olefin-based resin and a second resin, wherein the second resin has a temperature at which a loss tangent thereof exhibits a maximum value as measured by dynamic viscoelasticity measurement at a frequency of 1Hz and a strain of 0.3% of-10 ℃ or lower. In this case, the impact resistance of the resin molded article can be further improved.

The loss tangent can be determined by measurement in accordance with JIS K7244-4. Specifically, a test plate 5mm wide by 24mm long by 0.3mm thick was prepared, and the test plate was obtained by measuring the temperature dispersion of the dynamic viscoelasticity under the conditions of 0.3% strain, 1Hz frequency and 3 ℃/min temperature rise rate. The measurement of the temperature dispersion of dynamic viscoelasticity can be performed, for example, by using a dynamic viscoelasticity measuring apparatus (manufactured by Rheometrics, Inc., trade name "RSA").

As the first resin, the polyolefin described above can be used. The second resin is not particularly limited, and a vinyl aromatic block copolymer having a polymer of a vinyl aromatic monomer is preferable. More preferably a block copolymer having the aromatic vinyl block and a diene block which is a copolymer of conjugated diene monomers.

The aromatic vinyl monomer is not particularly limited, but may be, for example: styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α -methylstyrene, 2, 4-dimethylstyrene, 2, 4-diisopropylstyrene, 4-tert-butylstyrene, and the like.

The conjugated diene monomer is not particularly limited, and may be, for example, a conjugated diene having 4 to 12 carbon atoms such as butadiene, isoprene, piperylene, and dimethylbutadiene.

The copolymer having ethylene and aromatic blocks as described above includes a styrene-based elastomer.

Specific examples of the styrene-based elastomer include: copolymers such as styrene-butadiene copolymer (SB), styrene-butadiene-styrene copolymer (SBs), styrene-isoprene copolymer (SI), styrene-isoprene-styrene copolymer (SIs), styrene-ethylene-butylene copolymer (SEB), styrene-ethylene-butylene-styrene copolymer (SEBs), styrene-ethylene-propylene copolymer (SEP), and styrene-ethylene-propylene-styrene copolymer (SEPs). These copolymers may be block copolymers. Further, the shape may be linear or radial. These copolymers may be used alone or in combination of two or more. The styrene-based elastomer is preferably a styrene-ethylene-butylene-styrene block copolymer (SEBS) from the viewpoint of further improving the impact resistance of the resin molded article. In the present invention, the loss tangent may be within the above range, and another polymer such as polyolefin may be used as the second resin.

The content of the first resin is preferably 60 parts by weight or more, more preferably 80 parts by weight or more, preferably 95 parts by weight or more, and more preferably 90 parts by weight or less, relative to 100 parts by weight of the thermoplastic resin. When the content of the first resin is within the above range, the elastic modulus and heat resistance of the resin molded article are further improved.

The content of the second resin is preferably 5 parts by mass, more preferably 10 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 20 parts by mass with respect to 100 parts by mass of the thermoplastic resin. When the content of the second resin is within the above range, the impact resistance of the resin molded article can be further improved.

(first to third flaky graphite particles)

The graphite particles constituting the resin composition may be, for example, at least one kind of flaky graphite particles selected from the first to third flaky graphite particles. In addition, other graphite particles may be further contained.

The flaky graphite constituting the first to third flaky graphite particles is not particularly limited, and graphite, exfoliated graphite, graphene, or the like can be used. From the viewpoint of further improving the heat diffusibility, graphite or exfoliated graphite is preferable, and exfoliated graphite is more preferable. Further, from the viewpoint of further improving the impact resistance, graphite or flaked graphite is preferable, and graphite is more preferable. These flaky graphite may be used alone or in combination of a plurality of them. The flaked graphite is graphite obtained by subjecting raw graphite to a peeling treatment, and is a graphene sheet laminate thinner than the raw graphite. The number of graphene sheets in the exfoliated graphite is preferably smaller than that of the original graphite.

The average particle diameter of the first flaky graphite particles is preferably 1 μm or more, more preferably 5 μm or more, preferably 20 μm or less, and more preferably 15 μm or less.

When the average particle diameter of the first flake graphite particles is too small, the particles tend to aggregate during melt molding, and very brittle secondary particles are formed, thereby lowering the impact resistance. When the average particle size is too large, the area of one particle becomes large, and the peeled area further increases upon receiving an impact, so that the resin molded product is broken.

In the present specification, the average particle size refers to a mass value calculated from a volume standard distribution by a laser diffraction method using a laser diffraction/scattering particle size distribution measuring apparatus.

The content of the first flaky graphite particles is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, preferably 120 parts by mass or less, and more preferably 100 parts by mass or less, with respect to 100 parts by mass of the thermoplastic resin. When the content of the first flaky graphite particles is not less than the lower limit, the heat dissipation properties in the plane direction of the resin molded body can be further improved. Further, when the content of the first flaky graphite particles is too large, the interfacial area as a fracture origin becomes large, and therefore, when the content of the first flaky graphite particles is not more than the upper limit, the impact resistance can be further improved.

The aspect ratio of the first flaky graphite particles is preferably 3 or more, more preferably 10 or more, further preferably 30 or more, particularly preferably 50 or more, preferably 300 or less, more preferably 200 or less, further preferably 100 or less. When the aspect ratio of the first flaky graphite particles is not less than the lower limit, the heat dissipation properties in the plane direction can be further improved. When the aspect ratio of the first flaky graphite particles is not more than the upper limit, the first flaky graphite particles are less likely to round during molding. In the present specification, the aspect ratio is a ratio of a maximum dimension of the first flaky graphite particles in the stacking plane direction to a thickness of the first flaky graphite particles.

The thickness of the flaky graphite particles such as the first flaky graphite particles can be measured, for example, by using a projection electron microscope (TEM) or a Scanning Electron Microscope (SEM). From the viewpoint of further easy observation, it is desirable that a test piece cut out from a resin molded body is heated at 600 ℃ to scatter the resin, and observed by a projection electron microscope (TEM) or a Scanning Electron Microscope (SEM). The test piece may be cut along the main surface of the resin molded body or along a plane perpendicular to the main surface of the resin molded body, as long as the thickness of the flaky graphite particles can be measured while the resin is scattered. The resin molded article of the present invention may further contain second flake graphite particles different from the first flake graphite particles. The average particle diameter of the second flake graphite particles is preferably 0.1 μm or more and less than 40 μm. By setting the average particle diameter of the second flake graphite particles within the above range, both heat dissipation properties and impact resistance can be further improved. The first flaky graphite particles and the second flaky graphite particles are preferably tightly packed in the surface. In this case, the heat dissipation in the plane direction can be further improved.

When the average particle diameter of the first flaky graphite particles is d1 and the average particle diameter of the second flaky graphite particles is d2, it is preferable that 0.2. ltoreq. d1/d 2. ltoreq.0.6 is satisfied. When d2/d1 is within the above range, the smaller particles can enter the larger particle gaps, and the contact points between the flaky graphite particles are increased, whereby the heat conductivity and heat dissipation properties in the in-plane direction of the resin molded article are further improved. More preferably, it satisfies 0.25. ltoreq. d1/d 2. ltoreq.0.55, still more preferably satisfies 0.3. ltoreq. d1/d 2. ltoreq.0.5.

The sum of the contents of the first flaky graphite particles and the second flaky graphite particles is preferably 10 parts by mass or more, and preferably 150 parts by mass or less, per 100 parts by mass of the thermoplastic resin. When the sum of the contents of the first flaky graphite particles and the second flaky graphite particles is not less than the lower limit, the heat dissipation properties in the plane direction of the resin molded body can be further improved. Further, when the total content of the first flaky graphite particles and the second flaky graphite particles is too large, the interfacial area as the starting point of fracture becomes large, and therefore, when the total content of the first flaky graphite particles and the second flaky graphite particles is not more than the upper limit, the impact resistance can be further improved.

The resin molded article of the present invention may further contain third flaky graphite particles having an average particle diameter of 40 μm or more and 500 μm or less. When the third flaky graphite particles are included, the heat dissipation properties in the plane direction can be further improved. The first flaky graphite particles and the third flaky graphite particles are in plane, preferably tightly packed. In this case, the heat dissipation in the surface direction is further improved.

From the viewpoint of further improving the heat dissipation properties in the plane direction, the average particle diameter of the third flaky graphite particles is preferably 45 μm or more, more preferably 50 μm or more, preferably 150 μm or less, more preferably 100 μm or less.

When the average particle diameter of the first flaky graphite particles is d1 and the average particle diameter of the third flaky graphite particles is d3, it is preferable that 0.2. ltoreq. d1/d 3. ltoreq.0.6 is satisfied. When d1/d3 is within the above range, the smaller particles can enter the larger particle gaps and the flaky graphite particles come into contact with each other, whereby the heat conductivity and heat dissipation properties in the planar direction of the resin molded article can be further improved. More preferably 0.25. ltoreq. d1/d 3. ltoreq.0.55, still more preferably 0.3. ltoreq. d1/d 3. ltoreq.0.5.

The total content of the first flaky graphite particles and the third flaky graphite particles is preferably 10 parts by mass or more, and preferably 150 parts by mass or less, with respect to 100 parts by mass of the thermoplastic resin. When the sum of the contents of the first flaky graphite particles and the third flaky graphite particles is not less than the lower limit, the heat dissipation properties in the plane direction of the resin molded body can be further improved. Further, when the total content of the first flaky graphite particles and the third flaky graphite particles is too large, the interfacial area as the fracture origin increases, and therefore, when the total content of the first flaky graphite particles and the third flaky graphite particles is not more than the upper limit, the impact resistance can be further improved.

The content of the third flaky graphite particles is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, preferably 60 parts by mass or less, more preferably 50 parts by mass or less, further preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin. When the content of the third flaky graphite particles is within the above range, the heat dissipation properties in the plane direction can be further improved.

(exfoliated graphite)

The graphite particles constituting the resin composition may be exfoliated graphite. When the graphite sheet is contained, heat dissipation in the plane direction can be further improved. The exfoliated graphite may be used in combination with other graphite particles such as the first to third flaky graphite particles.

The flaked graphite is graphite obtained by subjecting raw graphite to a peeling treatment, and is a graphene sheet laminate thinner than the raw graphite. The exfoliation treatment to obtain exfoliated graphite may be a mechanical exfoliation method using a supercritical fluid, or may be a chemical exfoliation method using an acid treatment. The number of graphene sheets in the flake graphite is smaller than that in the original graphite.

The total content of the first to third flaky graphite particles and the exfoliated graphite is preferably 10 parts by mass or more and preferably 150 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. When the total content of the first to third flaky graphite particles and the flaked graphite is not less than the lower limit, the heat dissipation properties in the planar direction of the resin molded article can be further improved. Further, when the total content of the first to third flaky graphite particles and the exfoliated graphite particles is too large, the interfacial area as a fracture origin increases, and therefore, when the total content of the first to third flaky graphite particles and the exfoliated graphite particles is not more than the upper limit, the impact resistance can be further improved.

The content of the exfoliated graphite is a content corresponding to 100 parts by mass of the thermoplastic resin, and is preferably 50 parts by mass or less. When the content of the exfoliated graphite is too large, the peeling distance upon impact increases. The content of the exfoliated graphite is preferably 10 parts by mass or more, and more preferably 30 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

(surface treatment)

The graphite particles may be surface treated. When the graphite particles are surface-treated, secondary aggregation between the graphite particles can be prevented, and the impact resistance can be further improved. As the surface treatment agent, synthetic wax such as polyethylene; stearic acid and other natural waxes; or oxidized wax such as oxidized polyethylene wax.

(fiber-based Filler)

The resin molded article of the present invention may further contain a fibrous filler. The fibrous filler may be, for example, carbon fiber or glass fiber.

The content of the fibrous filler is not particularly limited, but is preferably 1 part by mass or more, and preferably 200 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin. When the content of the fibrous filler is within the above range, excellent fluidity can be further imparted to the resin composition of the resin molded article.

When the resin molded article of the present invention contains carbon fibers, the heat dissipation properties in the plane direction can be further improved. In this case, one of λ x and λ y can be further increased.

The carbon fiber is not particularly limited, and PAN type or pitch type carbon fiber or the like can be used. From the viewpoint of further improving heat dissipation properties, pitch-type carbon fibers having high thermal conductivity are preferable, and mesophase pitch-type carbon fibers are more preferable.

The total content of the first to third flaky graphite particles and the carbon fibers is preferably 10 parts by mass or more and preferably 150 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. When the total of the contents is not less than the lower limit, the heat radiation property in the plane direction of the resin molded body can be further improved. Further, when the total content of the first to third flaky graphite particles and the carbon fibers is too large, the interfacial area as a fracture origin increases, and therefore, when the total content of the first to third flaky graphite particles and the carbon fibers is not more than the upper limit, the impact resistance can be further improved. More preferably, the total content of the first flaky graphite particles and the carbon fibers is 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

The content of the carbon fiber is preferably 50 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. Since the fiber length of the carbon fiber is longer than that of the flaky graphite, when the content of the carbon fiber is too large, the separation distance may increase upon impact. The content of the carbon fiber is preferably 10 parts by mass or more, and more preferably 30 parts by mass or less, relative to 100 parts by mass of the thermoplastic resin.

(inorganic Filler)

The resin molded article of the present invention may contain an inorganic filler. The inorganic filler is not particularly limited, and talc, mica, carbon nanotubes, insulating heat conductive filler, or the like can be used. The insulating heat conductive filler is not particularly limited, and may be, for example, alumina, magnesia, boron nitride, aluminum nitride, or the like. These may be used alone or in combination of two or more. When the inorganic filler is contained, the mechanical strength of the resin molded product can be further improved. In particular, when the insulating heat conductive filler is used, the insulating property can be improved.

The total content of the first to third flaky graphite particles and the inorganic filler is preferably 10 parts by mass or more, and preferably 150 parts by mass or less, per 100 parts by mass of the thermoplastic resin. When the total content of the first to third flaky graphite particles and the inorganic filler is not less than the lower limit, the heat dissipation properties in the planar direction of the resin molded body can be further improved. Further, when the total content of the first to third flaky graphite particles and the inorganic filler is too large, the interfacial area as a fracture origin can be increased, and therefore, when the total content of the first to third flaky graphite particles and the inorganic filler is not more than the upper limit, the impact resistance can be further improved. The total content of the first flaky graphite particles and the inorganic filler is preferably 10 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

The average particle diameter of the inorganic filler is preferably 0.1 μm or more, and preferably less than 40 μm, from the viewpoint of further improving heat dissipation properties and impact resistance.

The content of the inorganic filler is not particularly limited, and the single phase is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 50 parts by mass or more, per 100 parts by mass of the thermoplastic resin. When the content of the insulating heat conductive filler is not less than the lower limit, the insulating property can be further improved. On the other hand, the content of the inorganic filler is preferably 100 parts by mass or less, and more preferably 70 parts by mass or less. The content of the inorganic filler is adjusted to the upper limit or less, and the heat dissipation property can be further improved.

(other additives)

Various additives may be added as optional components to the resin molded article. Examples of the additives include: antioxidants such as phenols, phosphorus, amines, and sulfur; ultraviolet absorbers such as benzotriazoles and hydroxyphenyltriazines; a metal loss preventive; halogenated flame retardants such as hexabromodiphenyl ether and decabromodiphenyl ether; flame retardants such as ammonium polyphosphate and trimethyl phosphate; various fillers; antistatic agents such as carbon black; a stabilizer; pigments, and the like. These may be used alone or in combination of two or more.

(resin molded article)

The resin molded body produced by using the resin composition can be subjected to plating processing. By performing the plating process, electromagnetic wave shielding properties and grounding properties required for a housing of an ECU or the like can be more effectively imparted.

The type of plating is not particularly limited, and copper plating is preferably performed. By using copper plating, heat dissipation and impact resistance can be further improved.

The electromagnetic wave shielding property (electromagnetic wave shielding performance, unit: dB) can be measured by the KEC method (KEC: abbreviation of "the Kyoho electronic industry Corp.). More specifically, it can be obtained as follows: the electric field intensity between a probe equipped with an antenna for transmitting a signal for transmitting an analog noise source and a probe equipped with a receiving antenna, and the electric field intensity when a sample is inserted between the two probes were measured. The measurement frequency may be set to 100MHz, for example.

(production method)

The resin molded article of the present invention can be produced, for example, by the following method.

First, a thermoplastic resin and a resin composition containing graphite particles such as first flaky graphite particles and exfoliated graphite are prepared. The resin composition may further contain the various materials. In the resin composition, the graphite particles are preferably dispersed in the thermoplastic resin. In this case, the impact resistance of the resin molded article obtained can be further improved. The method of dispersing the graphite particles in the thermoplastic resin is not particularly limited, but the graphite particles can be further uniformly dispersed by heating and melting the thermoplastic resin and kneading the thermoplastic resin with the graphite particles.

The kneading method is not particularly limited, and for example, a method of kneading under heating using a kneading apparatus such as a twin-screw kneader such as a kneader, a single-screw extruder, a twin-screw extruder, a banbury mixer, or a roll can be used. Among them, a method of melt kneading using an extruder is preferable.

Next, the prepared resin composition is molded by, for example, a method of press molding, extrusion lamination processing, injection molding, or the like to obtain a resin molded article.

In the present invention, various physical properties such as thermal conductivity in various directions and impact resistance can be appropriately adjusted by changing the kind of thermoplastic resin or graphite particles in the resin composition constituting the resin molded article, the compounding ratio of each component, and the like.

In the resin molded article of the present invention, the physical properties can be appropriately adjusted according to the intended use.

The effects of the present invention will be explained below by specific examples of the present invention and comparative examples.

The present invention is not limited to the following examples.

(example 1)

100 parts by mass of polypropylene (PP, trade name "E-150 GK" from Polymer K.K.) as a first thermoplastic resin and 100 parts by mass of flaky graphite particles (CNP 15, trade name R100 from Ito graphite K.K.) having an average particle diameter of 15 μm as first flaky graphite particles were melt-kneaded at 200 ℃ using an experimental kneader (trade name R100 from Toyo Seiki K.K.) to obtain a resin composition. The obtained resin composition was adjusted to have a length of 6mm, a width of 6mm and a height of 5mm, placed on a platen, and heated to 200 ℃. Then, the sheet was processed and formed into a sheet shape by a press plate under a pressure of 200MPa for 5 minutes. Subsequently, by pressing at ordinary temperature, a resin sheet 300mm in length, 300mm in width and 2mm in thickness was obtained.

Then, the obtained resin plate is baked in far infrared until the surface temperature reaches 200 ℃, heated and melted, and pressed by a mold at normal temperature to obtain a box-shaped resin forming body. Fig. 1(a) is a schematic plan view of the resulting resin molded body 1, and fig. 1(b) shows a schematic sectional view taken along the line a-a thereof. Thereafter, another resin molded body 1 is prepared in the same manner, and as shown in fig. 2, the peripheries of the pair of resin molded bodies 1 are clamped by a clamp 2, so that a box-shaped casing (casing 3) having a completely closed space is obtained.

(example 2)

A resin molded body and a housing were obtained in the same manner as in example 1, except that the amount of the first flaky graphite particles added was 60 parts by mass.

(example 3)

A resin molded article and a housing were obtained in the same manner as in example 1 except that 50 parts by mass of flaky graphite particles having an average particle diameter of 15 μm (product name of itanium graphite co., ltd. is "CNP 15", average particle diameter 15 μm) as the first flaky graphite particles and 50 parts by mass of flaky graphite particles having an average particle diameter of 35 μm (product name of itanium graphite co., ltd. is "CNP 35", average particle diameter 35 μm) as the second flaky graphite particles were used.

(example 4)

A resin molded article and a housing were obtained in the same manner as in example 1 except that 60 parts by mass of flaky graphite particles having an average particle diameter of 35 μm (trade name "CNP 35", average particle diameter 35 μm, manufactured by Ito graphite Co., Ltd.) as the first flaky graphite particles and 40 parts by mass of flaky graphite particles having an average particle diameter of 60 μm (trade name "Z-100", average particle diameter 60 μm, manufactured by Ito graphite Co., Ltd.) as the third flaky graphite particles were used.

(example 5)

A resin molded article and a housing were obtained in the same manner as in example 1 except that the amount of the first flaky graphite particles added was 80 parts by mass and 20 parts by mass of carbon fibers (trade name "XN-100" milled fibers, 50 μm in Fiber length, manufactured by Glass Fiber Co., Ltd., Japan) were further added.

(example 6)

The amount of polypropylene added was 70 parts by mass, and a resin composition was obtained by melt-kneading the components at 140 ℃ using a laboratory plasticator (Labo Plastomill) (product model "R100" manufactured by Toyo Seiki Seisaku-Sho K.K.) in the same manner as in example 1, except that 30 parts by mass of polyethylene (PE, product name "NOVATEC. TM. LJ 803", manufactured by polyethylene corporation, Japan) was used. The obtained resin composition was adjusted to have a length of 6mm, a width of 6mm and a height of 5mm, placed on a platen, and heated until the temperature reached 140 ℃. Then, the sheet was formed by press working under a pressure of 200MPa for 5 minutes. Next, the resulting sheet was pressed at room temperature to obtain a resin sheet having a length of 300mm, a width of 300mm and a thickness of 2 mm.

The obtained resin sheet was adjusted to 2mm × 5mm × 5mm sheet-like pellets, and the resin sheet of these sheet-like pellets was charged into a 160t injection molding machine. Then, a resin molded article having a box shape similar to that of example 1 was obtained by injecting the resin into a mold at a cylinder temperature of 200 ℃ during injection molding, cooling the resin to 60 ℃ and taking out the resin after 1 minute. The obtained resin molded article was handled in the same manner as in example 1, and the periphery thereof was clamped by clips to form a box-like case having a completely closed space.

(example 7)

A resin molded article and a housing were obtained in the same manner as in example 4 except that 60 parts by mass of flaky graphite particles having an average particle diameter of 7 μm (product name of itanium graphite co., ltd. is referred to as "PCH 7", average particle diameter of 7 μm) as the first flaky graphite particles were used in place of the first flaky graphite particles of example 4.

(example 8)

A resin molded article and a housing were obtained in the same manner as in example 1 except that 100 parts by mass of flaky graphite particles having an average particle diameter of 35 μm (trade name "CNP 35", 35 μm average particle diameter, manufactured by Ito graphite Co., Ltd.) as the first flaky graphite particles were used in place of the first flaky graphite particles in example 1.

(example 9)

A resin molded article and a housing were obtained in the same manner as in example 1, except that the first thermoplastic resin (polypropylene) in example 1 was changed to 80 parts by mass, and 20 parts by mass of a styrene-ethylene-butylene-styrene copolymer (SEBS, product name "Tuftec H1052" manufactured by asahi chemicals co., ltd.) as the second thermoplastic resin was further added.

(example 10)

A resin molded body and a housing were obtained in the same manner as in example 1 except that 50 parts by mass of the first thermoplastic resin (polypropylene) in example 1 was used, 50 parts by mass of an olefin elastomer (trade name "Engage 8407", manufactured by Dow Chemical) as the second thermoplastic resin was further added, and 100 parts by mass of flaky graphite particles (trade name "CNP 35", average particle size 35 μm ", manufactured by itanium graphite co.

(example 11)

Except for using 80 parts by mass of the first thermoplastic resin (polypropylene), 20 parts by mass of the second thermoplastic resin (olefin elastomer) and 80 parts by mass of the first flaky graphite particles in example 10, and further using 20 parts by mass of exfoliated graphite (trade name "UP-35N" manufactured by japan graphite co., ltd., average particle diameter 30 μm). A resin molded article and a housing were obtained in the same manner as in example 1.

(example 12)

A resin molded article and a housing were obtained in the same manner as in example 11, except that 100 parts by mass of a mixture (product name "V7100" manufactured by Primer Polymer co., ltd.) containing 80 parts by mass of a polypropylene resin (PP) and 20 parts by mass of a glass fiber was used in place of the first thermoplastic resin (polypropylene) and the exfoliated graphite in example 11.

(example 13)

A resin molded article and a housing were obtained in the same manner as in example 11, except that 20 parts by mass of talc (product name "MICRO ACE MS-K", manufactured by Nippon Talc Co., Ltd.) was used in place of the exfoliated graphite in example 11.

(example 14)

A resin molded article and a housing were obtained in the same manner as in example 11, except that 40 parts by mass of the first flaky graphite particles in example 11 were changed, 30 parts by mass of the second flaky graphite particles (product name "CNP 15" manufactured by itao graphite co., ltd., average particle diameter 15 μm) having an average particle diameter of 15 μm were further added, 30 parts by mass of the third flaky graphite particles (product name "Z-100" manufactured by itao graphite co., ltd., average particle diameter 60 μm) having an average particle diameter of 60 μm were further added, and no exfoliated graphite was added.

(example 15)

A resin molded article and a housing were obtained in the same manner as in example 4, except that 50 parts by mass of flaky graphite particles having an average particle size of 7 μm (product name PCH7, average particle size 7 μm, manufactured by itao graphite co., Ltd.) as the first flaky graphite particles, 30 parts by mass of flaky graphite particles having an average particle size of 35 μm (product name CNP35, average particle size 35 μm, manufactured by itao graphite co., Ltd.) as the second flaky graphite particles, and 20 parts by mass of flaky graphite particles having an average particle size of 120 μm (product name "F # 2", product name 120 μm, manufactured by japan graphite co., Ltd.) as the third flaky graphite particles were used.

(example 16)

A resin molded article and a housing were obtained in the same manner as in example 10, except that a cyclic olefin elastomer (COC, product name "8007" manufactured by polyplasics corporation) was used as the first thermoplastic resin instead of polypropylene.

(example 17)

A resin molded article and a housing were obtained in the same manner as in example 11, except that polyamide 6 (product name "CM 1007" manufactured by toray corporation) was used as the first thermoplastic resin instead of the polypropylene, the first flaky graphite particles were not used, and the amount of the flaked graphite (product name "UP-35N" manufactured by japan graphite co., ltd., average particle diameter 30 μm) added was 60 parts by mass.

(example 18)

A resin molded article and a housing were obtained in the same manner as in example 17, except that a styrene-ethylene-butylene-styrene copolymer (SEBS, product name "Tuftec H1052" manufactured by asahi chemicals) was used as the second thermoplastic resin instead of the olefin elastomer, and the amount of the flaked graphite (product name "UP-35N" manufactured by japan graphite co., ltd., average particle size 30 μm) was changed to 20 parts by mass.

(example 19)

A resin molded body and a housing were obtained in the same manner as in example 10, except that the amount of the first flaky graphite particles added was changed to 150 parts by mass.

(example 20)

A resin molded article and a shell were obtained in the same manner as in example 19, except that 90 parts by mass of flaky graphite particles having an average particle diameter of 7 μm (trade name "PCH 7", average particle diameter 7 μm, manufactured by itanium graphite co., Ltd.) as the first flaky graphite particles and 10 parts by mass of flaky graphite particles having an average particle diameter of 120 μm (trade name "F # 2", average particle diameter 120 μm, manufactured by japan graphite co., Ltd.) as the third flaky graphite particles were used.

(example 21)

A resin molded article and a housing were obtained in the same manner as in example 19, except that 50 parts by mass of flaked graphite (trade name "UP-35N", average particle diameter 30 μm, manufactured by Nippon graphite Co., Ltd.) was used in place of the first flaky graphite particles.

(example 22)

A resin molded article and a housing were obtained in the same manner as in example 10 except that a cyclic olefin copolymer (COC, product name "8007" manufactured by polyplasics corporation) was used as the first thermoplastic resin in place of polypropylene, and 100 parts by mass of flake graphite particles having an average particle diameter of 7 μm (product name "PCH 7", product name "7 μm" manufactured by ita graphite corporation) were used as the first flake graphite particles.

(example 23)

A resin molded article and a housing were obtained in the same manner as in example 10, except that 150 parts by mass of the first flaky graphite particles (product name "PCH 7" of itanium graphite co., ltd., average particle diameter 7 μm) having an average particle diameter of 7 μm were used.

(example 24)

The same procedures as in example 19 were repeated except for using 70 parts by mass of first flaky graphite particles having an average particle size of 7 μm (trade name "PCH 7", average particle size 7 μm, manufactured by ita graphite co., ltd.) and 30 parts by mass of flaked graphite particles having an average particle size of 100 μm (trade name "iGrafen- α", average particle size 100 μm, manufactured by ITEC corporation).

(example 25)

A resin molded article and a housing were obtained in the same manner as in example 19, except that 80 parts by mass of the first flaky graphite particles (product name PCH7, average particle size 7 μm, manufactured by itao graphite co., ltd.) and 20 parts by mass of the first flaky graphite particles (product name "iGrafen- α", product name 100 μm, manufactured by ITEC) were used.

(example 26)

A resin molded article and a housing were obtained in the same manner as in example 11, except that an acrylic-butadiene-styrene resin (ABS, product name "style IM 30" available from asahi chemicals) was used instead of polypropylene as the first thermoplastic resin, and the amount of flaked graphite (product name "UP-35N" available from japan graphite corporation, average particle diameter 30 μm) was 60 parts by mass without using the first flaky graphite particles.

(example 27)

A resin molded article and a housing were obtained in the same manner as in example 19, except that 90 parts by mass of the first flaky graphite particles (product name "PCH 7" manufactured by itao graphite co., ltd., average particle diameter 7 μm) having an average particle diameter of 7 μm were used, and 10 parts by mass of the first flaky graphite particles were further used, wherein the first flaky graphite particles had an average particle diameter of 100 μm (product name "iGrafen- α" manufactured by ITEC co., ltd., average particle diameter 100 μm).

(example 28)

A resin molded article and a housing were obtained in the same manner as in example 17, except that syndiotactic polystyrene (product name "S105" manufactured by seikagaku corporation, SPS) was used as the first thermoplastic resin in place of the polyamide 6.

(example 29)

A resin molded article and a housing were obtained in the same manner as in example 1, except that copper plating of 10 μm was applied as the plating.

Comparative example 1

A resin molded article and a housing were obtained in the same manner as in example 1 except that 100 parts by mass of spheroidal graphite (trade name "SG-BL 40", 40 μm average particle diameter, manufactured by Ito graphite Co., Ltd.) was used in place of the first flaky graphite particles in example 1.

Comparative example 2

A resin molded article and a housing were obtained in the same manner as in example 1 except that 100 parts by mass of flaky graphite particles having an average particle diameter of 60 μm (trade name "Z-100" manufactured by Ito graphite Co., Ltd., average particle diameter of 60 μm) were used in place of the first flaky graphite particles in example 1.

Comparative example 3

A resin molded article and a housing were obtained in the same manner as in example 1 except that 150 parts by mass of flaky graphite particles having an average particle diameter of 60 μm (trade name "Z-100" manufactured by Ito graphite Co., Ltd., average particle diameter of 60 μm) were used in place of the first flaky graphite particles in example 1.

Comparative example 4

A resin molded article and a housing were obtained in the same manner as in example 1 except that 100 parts by mass of carbon fibers (trade name "XN-100" milled fibers, 50 μm in Fiber length, manufactured by Glass Fiber Co., Ltd.) were used in place of the first flaky graphite particles in example 1.

Comparative example 5

A resin molded article and a housing were obtained in the same manner as in example 1, except that a cyclic olefin copolymer (product name "8007" manufactured by polyplastic corporation) was used instead of polypropylene as the first thermoplastic resin, and 100 parts by mass of flaky graphite particles having an average particle diameter of 120 μm (product name "F # 2" manufactured by japan graphite corporation, average particle diameter 120 μm) were used instead of the first flaky graphite particles.

Comparative example 6

A housing was obtained in the same manner as in comparative example 5, except that polyamide 6(PA, manufactured by toray corporation, trade name "CM 1007") was used instead of COC.

Comparative example 7

A resin molded article and a housing were obtained in the same manner as in example 1, except that 5 parts by mass of flaky graphite particles having an average particle diameter of 60 μm (trade name "Z-100" manufactured by Ito graphite Co., Ltd., average particle diameter of 60 μm) were used in place of the first flaky graphite particles.

Comparative example 8

A resin molded article and a housing were obtained in the same manner as in example 1, except that 210 parts by mass of flaky graphite particles having an average particle diameter of 7 μm (trade name "PCH 7", average particle diameter of 7 μm, manufactured by Ito graphite Co., Ltd.) were used in place of the first flaky graphite particles.

(evaluation method)

The resin molded bodies and housings obtained in examples and comparative examples were evaluated as follows. The results are shown in tables 1 to 3 below.

Ethylene component content;

the ethylene content (concentration) was measured in the following manner. First, in the propylene monomer resin, a known styrene- α -olefin copolymer (trade name "Engage 8100" manufactured by Dow Chemical corporation, ethylene content: 58 mass%) was precisely weighed and blended at a ratio of 5 mass%, 10 mass%, 20 mass%, and 30 mass%, and was completely dissolved in hot xylene. The solution obtained by dissolving was applied to a glass plate to prepare a film, and the absorption of polypropylene (1304 cm) by the polypropylene-based resin was measured under the following infrared spectroscopic measurement conditions^-1) And absorption of polyethylene (720 cm)^-1) Is suckedAnd (5) performing photometric comparison to prepare a detection standard curve. The thermoplastic resins used in the examples and comparative examples were similarly formed into films, and then measured under the following infrared spectroscopic measurement conditions, and the ethylene content was calculated using the standard lines for detection prepared by the above-described methods.

The measurement conditions were as follows: manufactured by Thermo Electron Corporation under the product name NICOLET6700

Measuring frequency: 4000-500cm^-1

Decomposition energy: 4cm^-1

The scanning times are as follows: 32 times (twice)

Volume average particle diameter (average particle diameter)

The volume average particle diameter of the graphite particles was measured by a particle diameter analysis-laser diffraction/scattering method in accordance with JIS Z8825.

Specifically, a test piece cut out from a resin molded body (housing) was heated at 600 ℃ to scatter the resin, and the graphite particles were taken out. The obtained graphite particles were put into an aqueous soap solution (neutral detergent: containing 0.01%) to have a concentration of 2 wt%, and irradiated with ultrasonic waves of 300W output for 1 minute using an ultrasonic homogenizer to obtain a suspension. Then, the suspension was measured for the volume particle size distribution of graphite particles using a laser diffraction/scattering particle size analyzer (product name "Microtrac MT 3300" manufactured by japan ltd.) and the cumulative 50% value of the volume particle size distribution was calculated as the average volume particle size of the graphite particles.

The number of particle size peaks, d1/d2, p/p 2;

the number of particle diameter peaks was determined from the volume particle size distribution obtained in the column of the volume average particle diameter. Fig. 7 is a graph showing the volume particle size distribution of the graphite particles of example 14. For example, for the graphite particles of fig. 7, there are 2 particle size peaks. The same operations as in example 14 were carried out for the other examples and comparative examples, and the number of particle size peaks, d1/d2, and p1/p2 were calculated.

In the volume average particle size distribution of the graphite particles, the volume average particle size is in the range of 150 μm or less, d1 represents the volume average particle size of the smallest particle size peak, and d1/d2 represents the ratio of the volume average particle size of the graphite particles constituting the largest particle size peak to d 2. For example, in fig. 7, the volume average particle diameter constituting the particle diameter peak indicated by the arrow a is d1, and the volume average particle diameter constituting the particle diameter peak indicated by the arrow B is d 2.

The volume average particle diameter of the graphite particles was in the range of 150 μm or less, and when the peak frequency of the minimum particle diameter peak was p1 (%), and the peak frequency of the maximum particle diameter peak was p2 (%), p1/p2 was determined from the ratio thereof. For example, in fig. 7, the peak frequency of the particle size peak shown by the arrow a is p1 (%), and the peak frequency of the particle size peak shown by the arrow B is p2 (%).

Shape and average radial thickness:

the shape and the average radial thickness were measured by using a scanning electron microscope (SEM, product name "JSM-6330F" manufactured by Japan Electron Co., Ltd.). Specifically, a test piece cut out of a resin molded body (housing) was heated at 600 ℃ to scatter the resin, and then graphite particles were taken out, placed on a stage, observed for shape by a scanning electron microscope, and the thickness of the graphite particles was calculated.

Specific gravity;

the obtained resin molded article was pelletized, pressed at 230 ℃ under a pressure of 15MPa to prepare a pellet, and the specific gravity of the resin molded article (housing) was measured by the underwater substitution method in accordance with JIS K7112.

Loss is compared with the tangent temperature;

the loss tangent temperature, which is the temperature at which the maximum value of loss tangent is exhibited, was measured in accordance with JIS K7244-4. Specifically, the obtained resin molded article was prepared as a test piece having a width of 5mm, a length of 24mm and a thickness of 0.3 mm. The test piece thus obtained was subjected to temperature dispersion measurement of dynamic viscoelasticity under conditions of a strain amount of 0.3%, a frequency of 1Hz, and a temperature rise rate of 3 ℃ for minutes. The temperature dispersion of dynamic viscoelasticity was measured by a dynamic viscoelasticity measuring apparatus (manufactured by Rheometrics, Inc., trade name: RSA).

Measuring the thermal conductivity;

a test piece having a size of 100mm X100 mm was cut from the bottom surface of the housing and used for measuring the thermal conductivity.

When an arbitrary direction of a plane or a curved surface of a test piece constituting the housing is an x direction, a direction perpendicular to the x direction is a y direction, and a thickness direction of the test piece is a z direction, a thermal conductivity λ x in the x direction, a thermal conductivity λ y in the y direction, and a thermal conductivity λ z in the z direction are measured by the following formulas.

Thermal conductivity (W/(m.k)). Thermometer (W) × specific gravity × specific thermal … (1)

In the formula (1), the diffusivities in the respective directions were measured using a product name "TA 33" manufactured by Bethel co. Using λ x, λ y, and λ z obtained from the formulas shown above, min (λ x, λ y/λ z, and λ x/λ y) is obtained.

In the case of evaluation by this method, the radiant heat of the xenon flash may not be detected in the in-plane direction, and the thickness of the detectable sample may be adjusted by melting and heating the sample cut out from the case, cooling and pressing the sample to reduce the thickness, if necessary.

The specific gravity was measured under the trade name "MDS-300" manufactured by ALFA MIRAGE. The specific heat was measured using a product name "DSC-6200" manufactured by Seiko Instruments.

Evaluation of Heat diffusibility (evaluation of Heat Release)

A test piece having a length of 100mm, a width of 100mm and a thickness of 1.6mm was cut from the bottom of the housing and used for the measurement of the thermal diffusivity.

For the evaluation of thermal diffusivity, a heater (product name "micro _ seramichester MS-5" manufactured by Sakakou electric heating Co., Ltd.) was disposed at the lower center part of the test piece, and 1g of heat-conductive lubricating oil (product name "GS-04" manufactured by AINEX Co., Ltd., thermal conductivity 3.8W/(m.k)) was uniformly applied between the test piece and the heater to join them, and a thermoelectric pair was fixed with a tape on the upper side of the test piece in contact with the heater directly above, and the temperature was measured by the thermoelectric pair, and it was noted that the thickness of the test piece was 1.6 mm.

The heater was heated at a voltage of 8V using a dc power supply, and the temperature of the upper center portion of the test piece was measured 800 seconds later (basically, the time until the temperature increased slowly and reached the saturation temperature). The lower this temperature, the lower the heat-soaking property, that is, the heat is being diffused to the surroundings, and it can be said that the housing has good heat dissipation performance.

Charpy impact resistance test:

the Charpy impact resistance test was carried out at room temperature under 23 ℃ conditions in accordance with JIS K7111. The test piece is obtained by cutting a basket body into a pellet-shaped product, and injection-molding the pellet-shaped product in a mold for molding the pellet-shaped product into a first test piece shape according to JIS K7111 at a cylinder temperature of 180 to 230 ℃ (appropriately adjusted depending on the material). The test piece thus obtained was processed into an A-shape according to JIS K7111 by using a notch-cutting machine (manufactured by Kayokoku Seisakusho K.K., trade name "No. 189 notch-cutting machine"). Then, the A-type cut based on JIS K7111 was subjected to a Charpy impact resistance test. The test apparatus used in the Charebye impact resistance test was a product name "No. 258 Universal impact tester", manufactured by Kayokoku Seisakusho K.K. The molding machine used for injecting the test piece into the mold was a product name "EC 160 NP" manufactured by toshiba mechanical co.

Falling ball impact strength:

the falling ball impact strength was measured as follows. First, the resin molded body was set on a horizontal surface in a thermostatic chamber at 23 ℃. Thereafter, iron balls (having a weight of 0.5kg) were allowed to naturally fall onto the upper surface of the resin molded body from a position of 0.1m in the vertical direction from the upper surface of the resin molded body. Whether the resin molded article was damaged by dropping the iron balls or not was visually observed. If the resin molded article was not broken, the iron balls naturally dropped from a position raised upward by 0.05m in the vertical direction, and whether or not the resin molded article was broken was visually observed. Therefore, the minimum height of the iron ball when the resin molded body was broken was measured by increasing the height at which the iron ball naturally falls at intervals of 0.05m until the resin molded body was broken. In tables 1 to 3, the unit of the minimum height of the iron ball falling is represented by cm.

Electromagnetic wave shielding properties;

the electromagnetic wave shielding property (electromagnetic wave shielding performance, unit; dB) was measured by the KEC method (KEC, short for the Kyoho electronic industry center). More specifically, the electric field intensity can be obtained by layering the electric field intensity between a probe with a signal transmission antenna for transmitting an analog noise source and a probe with a reception antenna, and the electric field intensity in the case where a sample is inserted between the two probes. The measurement frequency was set to 100 MHz.

As shown in tables 1 to 3, in examples 1 to 29, all of the evaluations of thermal diffusivity were 39.9 ℃ or lower, and the results of the Charpy impact resistance test were 2.1kJ/m²And a falling ball impact strength of 60cm or more. That is, it was confirmed that examples 1 to 29 all had both excellent heat dissipation properties and impact resistance.

Claims (14)

1. A resin molded body having thermal conductivity and a main surface,

the resin molded body contains a thermoplastic resin and graphite particles,

the graphite particles have a volume average particle diameter of 0.1 μm or more and less than 40 μm,

the graphite particles are contained in an amount of 10 to 200 parts by weight based on 100 parts by weight of the thermoplastic resin,

on the main surface, when an arbitrary direction is an x direction, a direction perpendicular to the x direction is a y direction, and a thickness direction of the resin molded body is a z direction,

the thermal conductivity in the x direction λ x, the thermal conductivity in the y direction λ y, and the thermal conductivity in the z direction λ z satisfy: min (lambdax, lambday)/lambdaz is not less than 3,

the main surface is a plane or a curved surface,

in the volume average particle size distribution of the graphite particles, when the peak frequency of the minimum particle size peak is p1 (%) and the peak frequency of the maximum particle size peak is p2 (%), 0.1. ltoreq. p1/p 2. ltoreq.0.9 is satisfied.

2. The resin molded body according to claim 1, wherein the λ x, the λ y, and the λ z satisfy min (λ x, λ y)/λ z ≧ 11.

3. The resin molded body according to claim 1 or 2, wherein the specific gravity is 1.0 or more and less than 1.4.

4. The resin molded body according to claim 1 or 2, wherein λ x and λ y satisfy λ x/λ y of 0.5 or more and 2 or less.

5. The resin molded body according to claim 1 or 2, wherein the λ z satisfies λ z < 2 (W/m-k).

6. The resin molded body according to claim 1 or 2, wherein the graphite particles have a plate shape.

7. The resin molded body according to claim 1 or 2, wherein an average radial thickness of the graphite particles is 0.1 μm or more and less than 10 μm.

8. The resin molded body according to claim 1 or 2, wherein in a range in which a volume average particle diameter in a volume average particle diameter distribution of the graphite particles is 150 μm or less, when a volume average particle diameter of the graphite particles constituting a minimum particle diameter peak is d1 and a volume average particle diameter of the graphite particles constituting a maximum particle diameter peak is d2, 0.1. ltoreq. d1/d 2. ltoreq.0.6 is satisfied.

9. The resin molded body according to claim 1 or 2, further comprising a fibrous filler.

10. The resin molded body according to claim 9, wherein a content of the fibrous filler is 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the thermoplastic resin.

11. The resin molded body according to claim 1 or 2, wherein the thermoplastic resin contains an olefin-based resin.

12. The resin molded body according to claim 11, wherein the olefin-based resin contains an ethylene component, and the content of the ethylene component is 5 to 40% by mass.

13. The resin molded body according to claim 1 or 2, wherein the temperature at which the maximum value of the loss tangent is exhibited by the resin molded body obtained by dynamic viscoelasticity measurement under the conditions of a frequency of 1Hz and a strain of 0.3% is 20 ℃ or less.

14. The resin molded body according to claim 1 or 2, which has a shape of a heat dissipation chassis, a heat dissipation casing or a heat sink.

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