JP7537169B2 - Thermoplastic resin composition, its manufacturing method, and electronic device - Google Patents

Description

The present invention relates to a thermoplastic resin composition and a manufacturing method thereof, and to an electronic device. More specifically, the present invention relates to a thermoplastic resin composition that can provide molded products having both high levels of rigidity and toughness (impact resistance), a manufacturing method thereof, and an electronic device that uses parts manufactured using the thermoplastic resin composition.

Resin compositions used to mold interior and exterior materials for office equipment and the like are required to produce resin parts that have both high rigidity and toughness. In particular, when thinner resin parts are required to reduce the size and weight of office equipment and the like, it is necessary to maintain the same level of rigidity and toughness as the parts before thinning, even when the thickness is reduced. In other words, resin compositions are required to have a composition that allows the resulting resin parts to have both high rigidity and toughness.

In response to such demands, Patent Document 1 discloses a resin composition in which a polypropylene resin is blended with a surface-modified inorganic filler and an elastomer of a specific structure, and describes how the molded article obtained thereby maintains a balance between rigidity and toughness. However, with the resin composition described in Patent Document 1, the molded article obtained has a large decrease in toughness due to the filler and a large decrease in rigidity due to the elastomer, and it is difficult to say that a high level of rigidity and toughness is achieved.

Furthermore, Patent Document 2 describes a flame-retardant resin composition that contains metal hydrate particles and a whitening inhibitor that satisfies the following (a) to (c):
(a) The average particle size (arithmetic mean diameter) calculated based on the volume-based particle size distribution measured using a laser light diffraction/scattering particle size distribution measuring device is in the range of 1 to 10 μm. (b) From a morphological photograph taken with a scanning electron microscope, it is observed that secondary particles consisting of aggregates formed from primary particles are included, and the length-average particle size based on the number-based particle size distribution in the major axis direction of the primary particles measured from the morphological photograph is in the range of 0.01 to 0.5 μm, with particles of 5 μm or more accounting for 0.1% or less. (c) The specific surface area measured by the BET method is 8.0 ^m2 /g or more.

In Patent Document 2, the shape and particle size of metal hydrate particles to be blended into a resin composition are specified based on three types of measurement methods in order to obtain a flame-retardant resin composition, particularly a polyolefin-based resin composition, that combines excellent ease of cutting (end cutting treatment) and resistance to scratching and whitening while maintaining flame retardancy and mechanical properties. However, this configuration does not impart both high levels of rigidity and toughness to the resin composition.

Japanese Patent Application Publication No. 5-311032 JP 2008-7723 A

The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved is to provide a thermoplastic resin composition that enables a molded article obtained using the thermoplastic resin composition to have both high levels of rigidity and toughness, and a method for producing the same. Also, the present invention is to provide an electronic device that includes a molded article produced using the above thermoplastic resin composition that has both high levels of rigidity and toughness.

Means for Solving the Problems The present inventors, in the course of investigating the causes of the above problems in order to solve the above problems, discovered that when inorganic fine particles having a specific average primary particle size are contained in a thermoplastic resin composition, a molded article obtained from the thermoplastic resin composition can have both high levels of rigidity and toughness by containing a specific number of agglomerated particles having a specific maximum diameter derived from the inorganic fine particles and in a specific ratio to the total particles, and thus arrived at the present invention.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. A thermoplastic resin composition containing a thermoplastic resin, inorganic fine particles, and a dispersant,
The inorganic fine particles have an average primary particle size in the range of 0.1 to 0.5 μm,
In an image of a cross section of an injection-molded product of the thermoplastic resin composition photographed with an electron microscope, ten visual fields of 150 μm×200 μm are randomly selected, and the number of agglomerated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm observed in the visual field is within a range of 5 to 20 on average in the 10 fields, and the ratio of the number of agglomerated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm to the total number of particles observed in the visual field is within a range of 0.1 to 1% on average in the 10 fields,
the content of the inorganic fine particles is within a range of 1 to 50 mass% based on the total amount of the thermoplastic resin composition,
The thermoplastic resin composition , wherein the content of the dispersant is within a range of 0.1 to 10 mass % based on the total amount of the thermoplastic resin composition .

2. The thermoplastic resin composition described in paragraph 1, characterized in that the constituent material of the inorganic fine particles is at least one selected from aluminum hydroxide, calcium carbonate, boehmite, silica, and kaolin.

3. The thermoplastic resin composition according to item 1 or 2 , wherein the dispersant is a fatty acid or a fatty acid metal salt.

4. The thermoplastic resin composition according to any one of items 1 to 3 , wherein the thermoplastic resin is a polypropylene-based resin.

5. An electronic device, comprising a molded article of the thermoplastic resin composition according to any one of items 1 to 4 as a part of the device.

6. A method for producing a thermoplastic resin composition according to any one of items 1 to 4 , comprising the steps of:
a first step of melt-kneading the thermoplastic resin, a portion of the inorganic fine particles, and the dispersant to obtain a resin mixture;
A second step of melt-kneading the resin mixture obtained in the first step and the remaining part of the inorganic fine particles to obtain a thermoplastic resin composition;
A method for producing a thermoplastic resin composition comprising the steps of:

7. The method for producing a thermoplastic resin composition according to item 6 , wherein the content of the inorganic fine particles in the resin mixture is within a range of 30 to 90 mass% of the total amount of the inorganic fine particles contained in the thermoplastic resin composition.

The above-mentioned means of the present invention can provide a thermoplastic resin composition that can provide a molded article having both high levels of rigidity and toughness, and a method for producing the same. It can also provide an electronic device that includes a molded article having both high levels of rigidity and toughness, produced using the above-mentioned thermoplastic resin composition.

Although the mechanism by which the effects of the present invention are expressed or acted upon has not been clarified, it is speculated as follows.

The thermoplastic resin composition of the present invention contains a thermoplastic resin, a dispersant, and inorganic fine particles with an average primary particle size of 0.1 to 0.5 μm. In the thermoplastic resin composition, the primary particles of the inorganic fine particles and aggregated particles formed by aggregation of these primary particles are mixed and dispersed, and this state is reflected in the molded product.

In the molded article obtained from the thermoplastic resin composition of the present invention, it is believed that upon impact, minute voids are formed at the interface between the primary particles of the inorganic fine particles and the thermoplastic resin, thereby absorbing the impact energy and improving the impact strength.

Here, generally, inorganic particles with a particle size larger than the above inorganic fine particles are used to impart rigidity to molded articles of thermoplastic resin compositions. However, in this case, it is known that the interface of the thermoplastic resin peels off upon impact, becoming the starting point of fracture, resulting in a decrease in impact strength.

In the molded article obtained from the thermoplastic resin composition of the present invention, the role of providing rigidity is given to the aggregated particles of the inorganic fine particles instead of the inorganic particles having a large particle size. When impacted, the aggregated particles of the inorganic fine particles deform due to collisions between the primary particles in the aggregated particles and the aggregated particles themselves deform. As a result, in the molded article obtained from the thermoplastic resin composition of the present invention, peeling at the interface of the thermoplastic resin is limited and is less likely to become the starting point of fracture when impacted, and a decrease in impact strength can be suppressed, compared to when the inorganic particles having a large particle size are added.

Specifically, in a cross section of an injection molded product of a thermoplastic resin composition, a visual field of 150 μm x 200 μm has an average of 5 to 20 aggregated particles with a maximum diameter of 5 to 35 μm in 10 locations in the visual field, and the ratio of the number of aggregated particles with a maximum diameter of 5 to 35 μm to the total number of particles observed in the visual field is within a range of 0.1 to 1% in the average of 10 locations in the visual field, thereby suppressing the number and size of fracture origins and improving bending strength (imparting rigidity) without reducing impact strength.

An image of a cross section of an injection molded product of the thermoplastic resin composition 1 (present invention) obtained in the example taken with an electron microscope (500x magnification). An image of a cross section of an injection molded product of the thermoplastic resin composition 1 (present invention) obtained in the example taken with an electron microscope (5000x magnification). An image of a cross section of an injection molded product of the thermoplastic resin composition 7 (comparative example) obtained in the example, taken with an electron microscope (500x magnification). An image of a cross section of an injection molded product of the thermoplastic resin composition 7 (comparative example) obtained in the example, taken with an electron microscope (5000x magnification).

The thermoplastic resin composition of the present invention is a thermoplastic resin composition containing a thermoplastic resin, inorganic fine particles, and a dispersant, wherein the inorganic fine particles have an average primary particle diameter in the range of 0.1 to 0.5 μm, and in an image of a cross section of an injection-molded product of the thermoplastic resin composition photographed with an electron microscope, 10 viewing areas of 150 μm x 200 μm are randomly selected, and the number of aggregated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm observed in the viewing area is in the range of 5 to 20 on average in the 10 locations, and the ratio of the number of aggregated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm to the total particles observed in the viewing area is in the range of 0.1 to 1% on average in the 10 locations. This feature is a technical feature common to each of the following embodiments.

In an embodiment of the thermoplastic resin composition of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the constituent material of the inorganic fine particles is at least one selected from aluminum hydroxide, calcium carbonate, boehmite, silica, and kaolin.

In an embodiment of the thermoplastic resin composition of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the content of the inorganic fine particles is within the range of 1 to 50 mass % based on the total amount of the thermoplastic resin composition.

In an embodiment of the thermoplastic resin composition of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the dispersant is a fatty acid or a fatty acid metal salt.

In one embodiment of the thermoplastic resin composition of the present invention, from the viewpoint of manifesting the effects of the present invention, it is preferable that the content of the dispersant is within the range of 0.1 to 10 mass % based on the total amount of the thermoplastic resin composition.

As an embodiment of the thermoplastic resin composition of the present invention, it is preferable that the thermoplastic resin is a polypropylene-based resin, since the effects of the present invention are more pronounced.

The electronic device of the present invention is characterized in that a molded article made from the thermoplastic resin composition of the present invention is used as an electronic device part.

The method for producing a thermoplastic resin composition of the present invention is a method for producing a thermoplastic resin composition of the present invention, and is characterized by comprising a first step of melt-kneading the thermoplastic resin, a portion of the inorganic fine particles, and the dispersant to obtain a resin mixture, and a second step of melt-kneading the resin mixture obtained in the first step and the remaining portion of the inorganic fine particles to obtain a thermoplastic resin composition.

By carrying out the above-mentioned two melt-kneading processes, the inorganic fine particles added in the first process are melt-kneaded together with the dispersant and are dispersed in the form of mostly primary particles, while the inorganic fine particles added in the second process are less susceptible to the action of the dispersant and are more likely to form aggregated particles. This makes it possible to easily produce the thermoplastic resin composition of the present invention.

In one embodiment of the method for producing a thermoplastic resin composition of the present invention, the content of the inorganic fine particles in the resin mixture is preferably within a range of 30 to 90 mass % of the total amount of the inorganic fine particles contained in the thermoplastic resin composition.

The present invention, its components, and the forms and modes for implementing the present invention are described in detail below. Note that in this application, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits.

[Summary of Thermoplastic Resin Composition]
The thermoplastic resin composition of the present invention is a thermoplastic resin composition containing a thermoplastic resin, inorganic fine particles, and a dispersant, and satisfies the following requirements (1) to (3).
(1) The inorganic fine particles have an average primary particle size in the range of 0.1 to 0.5 μm.
(2) In an image of a cross section of an injection-molded product of the thermoplastic resin composition photographed with an electron microscope, ten viewing areas of 150 μm x 200 μm are randomly selected, and the number of agglomerated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm observed within the viewing areas is within the range of 5 to 20 on average for the ten viewing areas.
(3) The ratio of the number of aggregated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm to the total number of particles observed within the viewing area is within the range of 0.1 to 1% on average for the 10 locations.

In the above requirement (1), the average primary particle diameter of the inorganic microparticles is the volume-based median diameter (D50). The volume-based median diameter (D50) can be measured, for example, by a laser diffraction/scattering method using an LA-960S2 (manufactured by HORIBA, Inc.). In the following description, inorganic microparticles that satisfy the condition (1) are also referred to as inorganic microparticles (P).

The above requirements (2) and (3) are specifically measured by the following method. The cross section of an injection-molded product of a thermoplastic resin composition is formed by cutting out a thin sample from any part of a test piece that has been machined into any shape by an injection molding machine using a microtome equipped with diamond teeth. There are no particular limitations on the position or direction in which the cross section is cut from the test piece.

As an injection molding machine, for example, a J55ELII manufactured by Japan Steel Works, Ltd. is used. The cylinder temperature during injection molding is adjusted appropriately depending on the type of thermoplastic resin. The shape of the test piece can be the same as that of a test piece used for impact testing, etc., with a length of 80 mm, a width of 10 mm, and a thickness of 4 mm.

Regarding (2) above, the cross section formed above is observed at 500x magnification with a transmission electron microscope, for example, a JEM-2000FX (manufactured by JEOL Ltd.), at an accelerating voltage of 5.0 kV, and an image is taken. In the image, the thermoplastic resin is identified as a gray area that serves as the matrix. Agglomerated particles of inorganic fine particles (P) are identified as white areas. Note that with an observation at 500x magnification, it is difficult to identify inorganic fine particles (P) that exist in the state of primary particles. In general, it is possible to identify agglomerated particles of inorganic fine particles (P) with a maximum diameter of 1 μm or more.

In a field of view measuring 150 μm x 200 μm, the maximum diameter of the aggregated particles of the identified individual inorganic fine particles (P) whose entire image is captured within the field of view is measured, and the number of aggregated particles of inorganic fine particles (P) whose maximum diameter is in the range of 5 to 35 μm is determined. The image analysis is performed on 10 locations of the field of view (150 μm x 200 μm) randomly selected from the cross section formed above. Hereinafter, aggregated particles of inorganic fine particles (P) whose maximum diameter is in the range of 5 to 35 μm are also referred to as aggregated particles (A1).

In the above (3), for each region of the 150 μm × 200 μm field of view where (2) was measured, the magnification is increased to a level where the primary particles of the inorganic fine particles (P) can be observed, specifically, the number of all particles present in the field of view is determined at a magnification of 5000 times, and then the proportion of aggregated particles (A1) to the total number of particles is determined, and further, the average of 10 fields of view is determined. The analysis of the images in the above (2) and (3) can be performed using the image analysis software ImageJ.

In the above (2), the number of agglomerated particles (A1) is 5 to 20, preferably 10 to 18. The number of agglomerated particles (hereinafter also referred to as agglomerated particles (A2)) that is larger in maximum diameter than the agglomerated particles (A1) observed in the above visual field, i.e., that exceeds 35 μm, as determined by the same method as in the above (2), is preferably 3 or less on average at 10 locations, and more preferably none exists (hereinafter, the above requirement related to the number of agglomerated particles (A2) is also referred to as requirement (4)). In addition, the number of agglomerated particles that is smaller in maximum diameter than the agglomerated particles (A1) observed in the above visual field, i.e., that is less than 5 μm, is not particularly limited. Agglomerated particles with a maximum diameter of 1 μm or more and less than 5 μm are also referred to as agglomerated particles (A3) hereinafter. Agglomerated particles with a maximum diameter less than 1 μm are also referred to as agglomerated particles (A4) hereinafter. The number of aggregated particles (A3) is, for example, preferably in the range of 50 to 250, and more preferably in the range of 100 to 200 (hereinafter, the above requirement regarding the number of aggregated particles (A3) is also referred to as requirement (5)).

In the above (3), the ratio of the number of agglomerated particles (A1) to the number of all particles is 0.1 to 1%, and preferably 0.1 to 0.5%. The total particles are composed of primary particles and agglomerated particles of inorganic fine particles (P), and the agglomerated particles are composed of the above agglomerated particles (A1), agglomerated particles (A2), agglomerated particles (A3), and agglomerated particles (A4).

The ratio of agglomerated particles (A2) to the number of all particles observed in the above field of view, which is determined by the same method as in (3) above, is preferably 0.05% or less, and more preferably 0% (hereinafter, the above requirement related to the ratio of agglomerated particles (A2) is also referred to as requirement (6)). The ratio of agglomerated particles (A3) to the number of all particles observed in the above field of view is preferably 0.25 to 10%, and more preferably 0.25 to 5% (hereinafter, the above requirement related to the ratio of agglomerated particles (A3) is also referred to as requirement (7)). The primary particles and agglomerated particles (A4) are treated equally, and the total ratio thereof to the number of all particles observed in the above field of view is preferably 90 to 99%, and more preferably 95 to 99% (hereinafter, the above requirement related to the ratio of primary particles and agglomerated particles (A4) is also referred to as requirement (8)). Table I summarizes the number of (2) and the percentage [%] of (3) in the aggregated particles (A1), as well as the preferred ranges of the numbers of (4) and (5) and the percentages [%] of (6) to (8) for the other aggregated particles and primary particles.

The thermoplastic resin composition of the present invention contains inorganic fine particles (P) and a dispersant that satisfy the requirement (1), and by satisfying the requirements (2) and (3), a molded article obtained using the composition can achieve both high levels of rigidity and toughness. In addition to the requirements (2) and (3), it is preferable to satisfy one or more of the requirements (4) to (8) in order to enhance the effects of the present invention, and it is more preferable to satisfy all of the requirements (4) to (8).

[Composition of Thermoplastic Resin Composition]
The thermoplastic resin composition of the present invention contains a thermoplastic resin, inorganic fine particles (P), and a dispersant. The inorganic fine particles (P) are contained in the thermoplastic resin composition of the present invention so as to satisfy the above requirements (2) and (3).

(Thermoplastic resin)
In the present invention, known thermoplastic resins can be used as the thermoplastic resin without any particular limitation. Examples of the thermoplastic resin include polyolefin resins, polystyrene resins, acrylonitrile-butadiene-styrene copolymers (ABS resins), polycarbonate resins, and polyester resins such as polyethylene terephthalate. These resins may be used alone or in combination of two or more.

The thermoplastic resin preferably contains a polyolefin-based resin as a main component. The content of the polyolefin-based resin in the thermoplastic resin is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more, based on the total amount of the thermoplastic resin. In the thermoplastic resin composition of the present invention, it is particularly preferable that the thermoplastic resin consists only of a polyolefin-based resin.

The content of the thermoplastic resin in the thermoplastic resin composition of the present invention is the amount obtained by excluding the contents of the inorganic fine particles (P), the dispersant, and various other additives that are optionally contained from the thermoplastic resin composition.

In the thermoplastic resin composition of the present invention, the content of the thermoplastic resin can be about 40 to 98% by mass, preferably 50 to 90% by mass, and more preferably 60 to 80% by mass, based on the total amount of the thermoplastic resin composition, from the viewpoint of the balance between rigidity and toughness.

<Polyolefin resin>
A polyolefin resin is a homopolymer or copolymer polymerized with an olefin as the main monomer component. In this specification, "olefin" refers to an aliphatic chain unsaturated hydrocarbon having one double bond.

Here, the main component constituting the resin (polymer) refers to a component that is 50% by mass or more of the total monomer components constituting the polymer. Polyolefin-based resins are homopolymers or copolymers that contain olefins in an amount of preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 80 to 100% by mass of the total monomer components.

Olefin copolymers include copolymers of olefins and other olefins, or copolymers of olefins and other monomers copolymerizable with olefins. The content of the other monomers in the polyolefin resin is preferably 30% by mass or less, more preferably 0 to 20% by mass, of the total monomer components.

As the olefin, an α-olefin having 2 to 12 carbon atoms is preferable. Examples of the olefin include ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-butene, 1-hexene, 1-octene, and 1-decene. When polymerizing the polyolefin resin, one type of olefin may be used alone, or two or more types may be used in combination.

Other monomers copolymerizable with olefins include, for example, cyclic olefins such as cyclopentene and norbornene, and dienes such as 1,4-hexadiene and 5-ethylidene-2-norbornene. In addition, monomers such as vinyl acetate, styrene, (meth)acrylic acid and its derivatives, vinyl ether, maleic anhydride, carbon monoxide, and N-vinylcarbazole may also be used. When polymerizing the polyolefin resin, the above other monomers may be used alone or in combination of two or more. Note that "(meth)acrylic acid" means at least one of acrylic acid and methacrylic acid.

Specific examples of polyolefin resins include polyethylene resins whose main component is ethylene, such as high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE); polypropylene resins whose main component is propylene, such as polypropylene (propylene homopolymer), ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer, and ethylene-propylene-diene copolymer; polybutene; and polypentene.

Specific examples of polyolefin resins include ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer, polyketone, and copolymers produced with metallocene catalysts. Also included are those produced by chemically reacting or modifying these polymers, specifically ionomer resins, saponified EVA, and olefin elastomers produced by dynamic vulcanization in an extruder.

As the polyolefin-based resin, polyethylene-based resin and polypropylene-based resin are preferred, and polypropylene-based resin is more preferred. The stereoregularity of the structure derived from propylene in the polypropylene-based resin may be any of isotactic, syndiotactic, and atactic. As the polypropylene-based resin, polypropylene is more preferred.

(Inorganic fine particles (P))
The thermoplastic resin composition of the present invention contains inorganic fine particles (P) having an average primary particle diameter in the range of 0.1 to 0.5 μm. The inorganic fine particles (P) are primary particles and the primary particles The particles are dispersed in the thermoplastic resin composition so as to satisfy the above requirements (2) and (3). The aggregated/dispersed state of the inorganic fine particles (P) in the resin composition preferably further satisfies one or more of the above requirements (4) to (8), and more preferably satisfies all of them.

The inorganic fine particles (P) may be made of one type, or may be made of two or more different types. Here, different inorganic fine particles include those made of different constituent materials, as well as those made of the same constituent materials but with different average primary particle diameters. In other words, the inorganic fine particles (P) may be made of a single type or two or more types of constituent materials, or may be made of two or more different types of constituent materials.

When inorganic fine particles (P) are composed of two or more kinds, the average primary particle diameter of each inorganic fine particle constituting the inorganic fine particles (P) does not necessarily have to be in the range of 0.1 to 0.5 μm, and it is sufficient that the average primary particle diameter of the inorganic fine particles (P) as a mixture of each inorganic fine particle is in the range of 0.1 to 0.5 μm. In order to easily adjust the average primary particle diameter of the inorganic fine particles (P) within the specified range, when inorganic fine particles (P) are composed of two or more kinds, the average primary particle diameter of each inorganic fine particle constituting the inorganic fine particles (P) is preferably in the range of 0.1 to 0.5 μm. It is more preferable that the average primary particle diameter of the inorganic fine particles (P) is in the range of 0.2 to 0.4 μm.

The constituent material of the inorganic fine particles (P) is not particularly limited as long as it is an inorganic compound, but specific examples include aluminum hydroxide, calcium carbonate, boehmite, silica, kaolin, magnesium hydroxide, talc, mica, clay, calcium sulfate, barium sulfate, glass, carbon black, and graphite. Among these, from the viewpoint of economy and safety to the human body, at least one selected from aluminum hydroxide, calcium carbonate, boehmite, silica, and kaolin is preferable. The constituent material of the inorganic fine particles (P) may be one type or two or more types. The particle shape of the inorganic fine particles (P) is not particularly limited, and examples include spherical, spindle-shaped, plate-shaped, scaly, needle-shaped, and fibrous shapes.

The inorganic fine particles (P) may be surface-modified with a surface modifier in the state of primary particles, if necessary. Examples of surface modifiers that can be used for surface modification include alkylsilazane compounds such as hexamethyldisilazane (HMDS), alkylalkoxysilane compounds such as dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, methyltrimethoxysilane, and butyltrimethoxysilane, chlorosilane compounds such as dimethyldichlorosilane and trimethylchlorosilane, silicone oil, and silicone varnish. These surface modifiers may be used alone or in combination of two or more.

In the thermoplastic resin composition of the present invention, the content of inorganic fine particles (P) is preferably within the range of 1 to 50% by mass, and more preferably 2 to 35% by mass, relative to the total amount of the thermoplastic resin composition. The content of inorganic fine particles (P) per 100 parts by mass of thermoplastic resin is preferably 1 to 120 parts by mass, and more preferably 20 to 85 parts by mass. If the content of inorganic fine particles (P) is within the above range, it is easy to satisfy the above (2) and (3), and it is easy to achieve both rigidity and toughness in a molded product obtained using the thermoplastic resin composition of the present invention.

(Dispersant)
In the thermoplastic resin composition of the present invention, the dispersant acts on the interface between the thermoplastic resin and the inorganic fine particles (P) and has the function of adjusting the aggregation/dispersion state of the inorganic fine particles (P) in the thermoplastic resin composition. By containing a dispersant in the thermoplastic resin composition of the present invention, excessive aggregation of the inorganic fine particles (P) is suppressed, making it possible to satisfy the above requirements (2) and (3).

As the dispersant, one that acts on the interface between the thermoplastic resin and the inorganic fine particles (P) and has the function of improving the dispersibility of the inorganic fine particles (P) in the thermoplastic resin can be used. Specifically, the dispersant is preferably one that functions to improve the dispersibility by adsorbing to the surface of the inorganic fine particles (P) and making the surface hydrophobic, thereby making it easier for the inorganic fine particles (P) to enter between the thermoplastic resin molecules. Examples of the dispersant include fatty acids, fatty acid metal salts, fatty acid esters, fatty acid amides, higher alcohols, hardened oils, silane coupling agents, and alcohol phosphate esters. The dispersant is preferably a fatty acid or a fatty acid metal salt. As the dispersant, one of these may be used alone, or two or more may be used in combination.

As fatty acids, higher fatty acids are preferred, such as stearic acid, oleic acid, palmitic acid, linoleic acid, lauric acid, caprylic acid, behenic acid, montanic acid, etc. As fatty acid metal salts, metal salts of the above higher fatty acids are preferred, such as stearic acid salts, oleic acid salts, palmitic acid salts, linoleic acid salts, lauric acid salts, caprylic acid salts, behenic acid salts, montanic acid salts, etc., and the types of metals include Li, Na, K, Al, Ca, Mg, Zn, Ba, etc.

Examples of fatty acid esters include monoesters such as methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl erucate, methyl behenate, butyl laurate, butyl stearate, isopropyl myristate, isopropyl palmitate, octyl palmitate, coconut fatty acid octyl ester, octyl stearate, special beef tallow fatty acid octyl ester, lauryl laurate, stearyl long stearate, long-chain fatty acid higher alcohol ester, behenyl behenate, and cetyl myristate.

Furthermore, as fatty acid esters, it is possible to use heat-resistant special higher fatty acid esters such as neopentyl polyol long chain fatty acid esters, partial esterification products of neopentyl polyol long chain fatty acid esters, neopentyl polyol fatty acid esters, neopentyl polyol medium chain fatty acid esters, neopentyl polyol C9 chain fatty acid esters, dipentaerythritol long chain fatty acid esters, and complex medium chain fatty acid esters.

Examples of fatty acid amides include stearic acid amide, oleic acid amide, palmitic acid amide, linoleic acid amide, lauric acid amide, caprylic acid amide, behenic acid amide, and montanic acid amide. Examples of higher alcohols include octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol. Examples of hardened oils include hardened beef tallow oil and hardened castor oil.

In the thermoplastic resin composition of the present invention, the content of the dispersant is preferably within the range of 0.1 to 10 mass % relative to the total amount of the thermoplastic resin composition, and more preferably 0.5 to 5 mass %, from the viewpoint of adjusting the aggregation/dispersion state of the inorganic fine particles (P) so as to satisfy the above (2) and (3), and not inducing a decrease in the rigidity of the molded article obtained from the thermoplastic resin composition. The content of the dispersant is preferably 1 to 30 mass parts, and more preferably 5 to 20 mass parts, relative to 100 mass parts of the inorganic fine particles (P).

(Other additives)
In addition to the thermoplastic resin, inorganic fine particles (P) and dispersant, the thermoplastic resin composition of the present invention may contain known additives within the range not impairing the effects of the present invention. Examples of other additives include flame retardants, anti-drip agents, antioxidants, tougheners, etc.

<Flame retardants>
The flame retardant may be an organic flame retardant or an inorganic flame retardant. Examples of organic flame retardants include bromine compounds and phosphorus compounds. Examples of inorganic flame retardants include antimony compounds and metal hydroxides. It is preferable that at least a part of the flame retardant is a phosphorus compound. This is because phosphorus compounds are easy to impart high flame retardancy to the resin composition and are not environmentally toxic.

The phosphorus compound is typically a phosphate ester compound, and specific examples of phosphate esters include triphenyl phosphate, tris(nonylphenyl)phosphate, tris(2,4-di-t-butylphenyl)phosphate, distearyl pentaerythritol diphosphate, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphate, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphate, tributyl phosphate, bisphenol A bis-diphenyl phosphate, and aromatic condensed phosphate esters, of which aromatic condensed phosphate esters are particularly preferred. Flame retardants may be used alone or in combination of two or more.

<Anti-drip agent>
The anti-drip agent is added for the purpose of preventing dripping of the resin material during combustion and improving flame retardancy, and examples of the anti-drip agent include fluorine-based anti-drip agents, silicone rubbers, layered silicates, etc. The anti-drip agents may be used alone or in combination of two or more.

<Antioxidants>
Antioxidants include hindered phenols, phosphite antioxidants or a mixture of both.

<Toughener>
The toughener is, for example, a resin having rubber elasticity, which is used for the purpose of improving the flexibility, processability, impact resistance, etc. of the resin composition. As described above, when the toughener is added, it is expected that the stiffness will decrease as a side effect. Therefore, when using it, the content should be adjusted and care should be taken not to impair the effect of the present invention.

The toughener is preferably a thermoplastic elastomer containing a soft segment composed of a polymer of a monomer containing butadiene and a hard segment composed of a polymer of a monomer having an aromatic group such as styrene. Examples of the thermoplastic elastomer include methyl methacrylate-butadiene-styrene copolymer (MBS), acrylonitrile-butadiene-styrene copolymer (ABS), styrene butadiene styrene copolymer (SBS), and butyl acrylate-methyl methacrylate copolymer. In particular, it is preferable that the toughener is one or more selected from the group consisting of MBS and ABS from the viewpoints of compatibility and flame retardancy of the thermoplastic resin composition and dispersibility of the thermoplastic elastomer in the thermoplastic resin composition. The toughener may be used alone or in combination of two or more types.

The content of other additives in the thermoplastic resin composition of the present invention is within a range that does not impair the effects of the present invention, and is, for example, within a range of about 0.1 to 30% by mass, and preferably within a range of 0.1 to 20% by mass, relative to the total amount of the thermoplastic resin composition. In addition, a total of 30% by mass or less is preferable.

[Method of producing thermoplastic resin composition]
The thermoplastic resin composition of the present invention can be obtained by melt-kneading a thermoplastic resin, inorganic fine particles (P), a dispersant, and other additives that may be contained as necessary, so that the aggregation/dispersion state of the inorganic fine particles (P) satisfies the requirements of (2) and (3).

The thermoplastic resin composition of the present invention is preferably produced by a production method including, for example, a first step of melt-kneading a thermoplastic resin, a portion of the inorganic fine particles (P) and a dispersant to obtain a resin mixture, and a second step of melt-kneading the resin mixture obtained in the first step and the remaining inorganic fine particles (P) to obtain a thermoplastic resin composition, since this makes it easier for the aggregated/dispersed state of the inorganic fine particles (P) to satisfy the requirements of (2) and (3) in the obtained thermoplastic resin composition.

In addition, it is preferable that the majority of the thermoplastic resin and dispersant finally contained in the thermoplastic resin composition, for example 95 mass% or more of the total amount, are melt-kneaded in the first step, and it is preferable that the entire amount of each is melt-kneaded in the first step.

In the first step, the inorganic fine particles (P) are melt-kneaded in an amount of preferably 30 to 90% by mass of the total amount of inorganic fine particles (P) finally contained in the thermoplastic resin composition, and more preferably 45 to 80% by mass. In the second step, the remaining amount of inorganic fine particles (P) added in the first step is melt-kneaded with the resin mixture. That is, the amount of inorganic fine particles (P) in the second step is the amount obtained by subtracting the amount melt-kneaded in the first step from the total amount of inorganic fine particles (P) finally contained in the thermoplastic resin composition. Specifically, the amount of inorganic fine particles (P) in the second step is preferably 10 to 70% by mass of the total amount of inorganic fine particles (P), and more preferably 20 to 55% by mass.

In the first step, a part of the inorganic fine particles (P), preferably the amount in the above proportion relative to the total amount, is melted and kneaded with a thermoplastic resin and a dispersant to obtain a resin mixture in which a part of the inorganic fine particles (P) is dispersed as primary particles or aggregated particles with a sufficiently small maximum diameter by the action of the dispersant. Next, in the second step, the remaining part of the inorganic fine particles (P), preferably the amount in the above proportion relative to the total amount, is melted and kneaded with the resin mixture obtained in the first step, so that the remaining part of the inorganic fine particles (P) aggregates with almost no action of the dispersant to form aggregated particles with a large maximum diameter, for example, a maximum diameter of 5 μm or more.

In the thermoplastic resin composition thus obtained, the aggregated and dispersed state of the inorganic fine particles (P) satisfies the requirements (2) and (3). In the thermoplastic resin composition thus obtained, the aggregated and dispersed state of the inorganic fine particles (P) preferably further satisfies one or more of the above requirements (4) to (8), and more preferably satisfies all of them.

When the thermoplastic resin composition of the present invention contains other additives, the other additives may be melt-kneaded together with the thermoplastic resin, a portion of the inorganic fine particles (P) and the dispersant in the first step, and may be added to the resin mixture obtained in the first step together with the remaining inorganic fine particles (P) and melt-kneaded in the second step.

In the manufacturing method of the present invention, the melt kneading in the first and second steps is carried out using a kneading device such as a Banbury mixer, a roll, a plastograph, an extruder (such as a single-screw extruder or a multi-screw extruder (e.g., a twin-screw extruder)), or a kneader. Among these, it is preferable to use an extruder for melt kneading because of its good production efficiency. Furthermore, it is preferable to use a multi-screw extruder for melt kneading because it can impart high shear properties, and it is more preferable to use a twin-screw extruder. Here, the term extruder is used in a category that includes an extrusion kneader.

In the manufacturing method of the present invention, different kneading devices may be used for the first and second steps, but it is preferable to use an extruder, particularly a twin-screw extruder, for both steps.

The temperature during melt kneading (melt kneading temperature) is set to be equal to or higher than the melting temperature of the thermoplastic resin in both the first and second steps. When the thermoplastic resin is a polyolefin-based resin, the melt kneading temperature is preferably 150 to 280°C, for example, and is selected appropriately depending on the polyolefin-based resin used. When a polypropylene-based resin is used as the polyolefin-based resin, the melt kneading temperature is preferably 180 to 270°C, more preferably 180 to 230°C. Within the above temperature range, the melt kneading temperatures in the first and second steps may be the same or different. When an extruder is used for melt kneading, the kneading melt temperature corresponds to the cylinder temperature.

When an extruder is used for melt kneading, the screw rotation speed is preferably in the range of 50 to 300 rpm in both the first and second steps. The screw rotation speeds in the first and second steps may be the same or different. The discharge rate of the resin mixture or thermoplastic resin composition from the extruder in the first and second steps is preferably in the range of 1 to 50 kg/hr, respectively.

Before the melt-kneading step in the first step, the components may be mixed in advance using various mixers, such as a tumbler or a high-speed mixer known as a Henschel mixer.

In the manufacturing method of the present invention, the kneaded material is extruded into a strand shape in the second step, and then the kneaded material extruded into a strand shape can be processed into a pellet shape, a flake shape, or other shape.

The thermoplastic resin composition of the present invention can take various forms, such as powder, granules, tablets, pellets, flakes, fibers, and liquid.

When the thermoplastic resin composition of the present invention is used, the resulting molded article has high levels of rigidity and toughness.

For example, the flexural modulus of the molded article made from the thermoplastic resin composition of the present invention, as measured in a bending test carried out in accordance with JIS-K7171, is preferably 30 MPa or more, and more preferably 40 MPa or more. If the flexural modulus is 30 MPa or more, the rigidity of the molded article can be evaluated as being practically acceptable.

For example, the molded article formed from the thermoplastic resin composition of the present invention preferably has a Charpy impact strength of 10 kJ/ ^m2 or more, more preferably 15 kJ/ ^m2 or more, as measured in a Charpy impact test carried out in accordance with JIS-K7111. If the Charpy impact strength is 10 kJ/ ^m2 or more, the toughness of the molded article can be evaluated as being practically acceptable.

(Molded products)
A molded article can be produced using the thermoplastic resin composition of the present invention. This molded article can provide a product having both high levels of rigidity and toughness. When producing a molded article, the thermoplastic resin composition can be melted and molded in various molding machines. The molding method can be appropriately selected depending on the shape and application of the molded article, and examples of the molding method include injection molding, extrusion molding, compression molding, blow molding, calendar molding, and inflation molding. In addition, a sheet-like or film-like molded article obtained by extrusion molding, calendar molding, or the like can be subjected to secondary molding such as vacuum molding or pressure molding.

The molded articles molded from the thermoplastic resin composition of the present invention are not particularly limited, and examples thereof include electric and electronic parts, electrical components, exterior parts, and interior parts in the fields of home appliances and automobiles, as well as various packaging materials, household goods, office supplies, piping, and agricultural materials.

[Electronic devices]
The present invention can provide an electronic device characterized by using the above molded article as a mechanical part. The electronic device is not particularly limited, and examples thereof include office automation equipment such as computers, scanners, copiers, printers, facsimile machines, and multifunction machines called MFPs (Multi Function Peripherals) that combine the functions of these devices. The molded article molded from the thermoplastic resin composition of the present invention is preferably used as an exterior part of the electronic device.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these. In the examples, the terms "parts" and "%" are used, but unless otherwise specified, they represent "parts by mass" or "% by mass."

[Preparation of Thermoplastic Resin Composition]
The following commercially available products were prepared as raw material components to be contained in the thermoplastic resin composition. The abbreviations used in Table II are shown in parentheses after the general names of the raw material components.
<Thermoplastic resin>
・Polypropylene resin (PP): Prime Polypro J715M (product name, manufactured by Prime Polymer Co., Ltd.)

<Inorganic fine particles (P)>
Calcium carbonate particles (Ca carbonate): Calsees P (product name, manufactured by Konoshima Chemical Co., Ltd., average primary particle size: 0.2 μm, surface modified with fatty acid)
Aluminum hydroxide particles (Al(OH) ₃ ): KH-108 (product name, manufactured by Hayashi Kasei Co., Ltd., average primary particle size: 0.5 μm)
Boehmite particles (boehmite): BMB-03 (product name, manufactured by Kawai Lime Industry Co., Ltd., average primary particle diameter: 0.3 μm)
Silica particles (silica): NAX-50 (product name, manufactured by Evonik, average primary particle size: 0.1 μm, surface modified with HMDS)
Kaolin particles (kaolin): Hydrite TS90 (product name, manufactured by Hayashi Kasei Co., Ltd., average primary particle size: 0.3 μm)

<Dispersant>
Magnesium stearate (Ste-Mg): Daiwax M (product name, manufactured by Dainichi Chemical Industry Co., Ltd.)
Calcium stearate (Ste-Ca): Daiwax C (product name, manufactured by Dainichi Chemical Industry Co., Ltd.)
・Zinc stearate (Ste-Zn): Daiwax ZP (product name, manufactured by Dainichi Chemical Industry Co., Ltd.)
Lithium stearate (Ste-Li): Daiwax L (product name, manufactured by Dainichi Chemical Industry Co., Ltd.)

(Production of Thermoplastic Resin Composition 1)
Using a twin-screw extruder kneader "KTX-30" (manufactured by Kobe Steel, Ltd.), 84 parts by mass of polypropylene-based resin, 7.5 parts by mass of calcium carbonate particles, and 1 part by mass of magnesium stearate were melt-kneaded at a cylinder temperature of 190°C, a screw rotation speed of 200 rpm, and a discharge rate of 10 kg/hr to prepare resin mixture 1 (first step).

Next, 92.5 parts by mass of resin mixture 1 and 7.5 parts by mass of calcium carbonate particles were melt-kneaded using a twin-screw extruder kneader "KTX-30" (manufactured by Kobe Steel, Ltd.) at a cylinder temperature of 190°C, a screw rotation speed of 200 rpm, and a discharge rate of 10 kg/hr (second process), and the extruded kneaded product was pelletized to obtain pellet-shaped thermoplastic resin composition 1.

(Production of Thermoplastic Resin Compositions 2 to 10)
In the above, except that the types and contents of the thermoplastic resin, the inorganic fine particles (P) and the dispersant were changed as shown in Table II, the thermoplastic resin compositions were melt-kneaded twice in the first and second steps in the same manner as in the thermoplastic resin composition 1, and then pelletized to produce pellet-shaped thermoplastic resin compositions 2 to 10.

(Production of Thermoplastic Resin Compositions 11 and 12)
In the above, the types and contents of the thermoplastic resin, inorganic fine particles (P) and dispersant were changed as shown in Table II, and all the raw material components were melt-kneaded in one go using a twin-screw extruder kneader "KTX-30" (manufactured by Kobe Steel, Ltd.) under conditions of a cylinder temperature of 190°C, a screw rotation speed of 200 rpm and a discharge rate of 10 kg/hr, and then pelletized to produce pellet-shaped thermoplastic resin compositions 11 and 12.

<Measurement of the aggregation/dispersion state of inorganic fine particles (P)>
The thermoplastic resin compositions 1 to 12 obtained above were dried at 80 ° C. for 4 hours, and then a rectangular test piece having a length of 100 mm x width of 10 mm x depth of 1.6 mm was molded by an injection molding machine (J55ELII, manufactured by Japan Steel Works, Ltd.). A thin-section sample was cut out from any part of the obtained test piece using a microtome equipped with diamond teeth to prepare a measurement cross section. For 10 points randomly selected from the obtained measurement cross section, an image of a field of view having a size of 150 μm x 200 μm was taken at 500 times with an acceleration voltage of 5.0 kV using a transmission electron microscope (JEM-2000FX (manufactured by JEOL Ltd.)), and the following measurements and calculations of (1) and (2) were performed using the image analysis software ImageJ. The classification of the aggregated particles (A1) to (A4) is as described above.

(1) Number of agglomerated particles (A1) to (A3) In each of the above-mentioned viewing regions, the maximum diameter of the agglomerated particles of the specified individual inorganic fine particles (P) whose entire image was photographed in the viewing region was measured, and the numbers of agglomerated particles (A1) (5 μm≦D≦35 μm, D indicates the maximum diameter, and the same applies below), agglomerated particles (A2) (35 μm<D) and agglomerated particles (A3) (1 μm≦D<5 μm) were counted, and the average of 10 points was calculated. The results are shown in Table II.

Figure 1 shows an image of a 150 μm×200 μm field of view of the cross section of thermoplastic resin composition 1 taken at 500x magnification using a transmission electron microscope. In the image of Figure 1, the number of aggregate particles (A1) is measured to be 17, the number of aggregate particles (A2) is measured to be 0, and the number of aggregate particles (A3) is measured to be 215. Figure 3 shows an image of a 150 μm×200 μm field of view of the cross section of thermoplastic resin composition 7 taken at 500x magnification using a transmission electron microscope. In the image of Figure 3, the number of aggregate particles (A1) is measured to be 0, the number of aggregate particles (A2) is measured to be 0, and the number of aggregate particles (A3) is measured to be 3. Table II shows the average value of the number of aggregate particles (A1) to (A3) measured in this way for 10 images.

(2) Proportion of Aggregated Particles (A1) to (A3) and Primary Particles + Aggregated Particles (A4) For each of the above-mentioned viewing regions, the number of all particles present at a magnification of 5000 times, at which the primary particles of the inorganic fine particles (P) can be observed, was determined, and the proportions of the aggregated particles (A1) to (A3) and primary particles + aggregated particles (A4) (the sum of primary particles and aggregated particles (A4) (D < 1 μm)) to the total number of particles were determined, and further the average of 10 viewing regions was determined.

Figures 2 and 4 show images of a portion of the 150 μm × 200 μm field of view in which the above (1) is measured for thermoplastic resin composition 1 and thermoplastic resin composition 7, enlarged at a magnification of 5000 times. Image analysis is performed for the entire 150 μm × 200 μm field of view by combining the images enlarged at a magnification of 5000 times, counting the number of each particle in the region, and calculating the ratio of the number of each particle to the total number of particles.

<Evaluation>
The thermoplastic resin compositions 1 to 12 obtained above were evaluated for stiffness and toughness as follows, and the results are shown in Table II.

(1) Rigidity Evaluation After drying pellets of each thermoplastic resin composition at 80°C for 4 hours, they were molded into prismatic test pieces of 80 mm x 10 mm x 4 mm using an injection molding machine (J55ELII, manufactured by Japan Steel Works, Ltd.), and a three-point bending test was performed in accordance with JIS-K7171 to measure the flexural modulus [MPa] and evaluate it according to the following criteria. If the flexural modulus is 30 MPa or more, it can be evaluated that the rigidity of the molded product is practically acceptable.

(Evaluation Criteria)
◎: 40 MPa or more ◯: 30 MPa or more, less than 40 MPa △: 20 MPa or more, less than 30 MPa ×: less than 20 MPa

(2) Toughness Evaluation After drying the pellets of each thermoplastic resin composition at 80°C for 4 hours, a rectangular column-shaped test piece of 80 mm x 10 mm x 4 mm was prepared using an injection molding machine (J1 40AD-110H, manufactured by Japan Steel Works, Ltd.), and molded using a ROBOSHOT S-2000i50Bp (manufactured by Fanuc Corporation) so that a V-notch of 2 mm depth was formed in the center. The obtained V-notched test piece was subjected to a Charpy impact test in accordance with JIS-K7111, and the Charpy impact strength [kJ/m ² ] was measured and evaluated according to the following criteria. If the Charpy impact strength is 10 kJ/m ² or more, the toughness of the molded product is considered to be satisfactory for practical use.

(Evaluation Criteria)
◎: 15 kJ/ ^m2 or more 〇: 10 kJ/ ^m2 or more, less than 15 kJ/ ^m2 △: 5 kJ/ ^m2 or more, less than 10 kJ/ ^m2 ×: Less than 5 kJ/ ^m2

For thermoplastic resin compositions 1 to 12, the composition, the amount of materials added in each step of the manufacturing method, the state of aggregation and dispersion of the inorganic fine particles (P), and the evaluation results of the physical properties (rigidity and toughness) of the molded products are summarized in Table II.

From Table II, it can be seen that the molded articles obtained from the thermoplastic resin composition of the present invention have both high levels of rigidity and toughness.

Claims (7)

A thermoplastic resin composition containing a thermoplastic resin, inorganic fine particles, and a dispersant,
The inorganic fine particles have an average primary particle size in the range of 0.1 to 0.5 μm,
In an image of a cross section of an injection-molded product of the thermoplastic resin composition photographed with an electron microscope, ten visual fields of 150 μm×200 μm are randomly selected, and the number of agglomerated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm observed in the visual field is within a range of 5 to 20 on average in the 10 fields, and the ratio of the number of agglomerated particles of the inorganic fine particles having a maximum diameter of 5 to 35 μm to the total number of particles observed in the visual field is within a range of 0.1 to 1% on average in the 10 fields,
the content of the inorganic fine particles is within a range of 1 to 50 mass% based on the total amount of the thermoplastic resin composition,
The thermoplastic resin composition , wherein the content of the dispersant is within a range of 0.1 to 10 mass % based on the total amount of the thermoplastic resin composition . The thermoplastic resin composition according to claim 1, characterized in that the constituent material of the inorganic fine particles is at least one selected from aluminum hydroxide, calcium carbonate, boehmite, silica and kaolin. 3. The thermoplastic resin composition according to claim 1, wherein the dispersant is a fatty acid or a fatty acid metal salt. The thermoplastic resin composition according to any one of claims 1 to 3 , wherein the thermoplastic resin is a polypropylene-based resin. 5. An electronic device comprising a molded article of the thermoplastic resin composition according to claim 1 as a part of the device. A method for producing a thermoplastic resin composition according to any one of claims 1 to 4 , comprising the steps of:
a first step of melt-kneading the thermoplastic resin, a portion of the inorganic fine particles, and the dispersant to obtain a resin mixture;
A second step of melt-kneading the resin mixture obtained in the first step and the remaining part of the inorganic fine particles to obtain a thermoplastic resin composition;
A method for producing a thermoplastic resin composition comprising the steps of: The method for producing a thermoplastic resin composition according to claim 6 , characterized in that the content of the inorganic fine particles in the resin mixture is within a range of 30 to 90 mass% of the total amount of the inorganic fine particles contained in the thermoplastic resin composition.