KR20160068762A - Thermally conductive electrically insulating particles and compositions - Google Patents

Abstract

(a) a composite core made by compressing and shearing mixing a plurality of thermally conductive core particles and an organic binder, and (b) an insulating material at least partially coating the composite core, wherein the thermally conductive particles have a volume resistivity of at least 1 X 10 < ⁴ > to 1 x ¹⁰ < 10 >

Description

[0001] THERMALLY CONDUCTIVE ELECTRICALLY INSULATING PARTICLES AND COMPOSITIONS [0002]

Cross reference to related application

This application claims the benefit of priority from Japanese Patent Application No. 2013-209304, filed October 4, 2013, now pending.

Description of invention

Thermally conductive particles which are also electrically insulative, a resin composition containing the particles, and a method for producing the same are described in this specification.

In recent years, electronic devices such as LED modules and hand held have not only become smaller and more integrated, but also have greater performance, requiring greater heat dissipation and electrical isolation of components within these devices . As a result, thermally conductive particles having excellent electrical insulation properties have been sought as building blocks for materials used in electronic devices.

International Patent Application Publication No. WO2011 / 027757 discloses ceramic coated carbon particles, which are thermally conductive and are formed by bonding ceramic particles to carbon particles by adding a slurry of carbon particles to the slurry of ceramic particles. U.S. Patent No. 5,246,897 discloses coated graphite particles formed by a mechanical impact method in which graphite particles and coated particles are collided using a high velocity gas flow. U.S. Patent No. 7,588,826 discloses coated graphite particles formed by mechanical melting in the presence of an interactive functional agent.

Thermally conductive particles are described herein wherein the thermally conductive particles comprise an insulating material that at least partially coats the composite core and the composite core and the composite core is bonded together by an organic binder through a mechanofusion process, And the volume resistivity of the thermally conductive particles is in the range of at least 1 x 10 < ⁴ > to 1 x ¹⁰ < ¹⁰ > In addition, a resin composition is described herein, wherein the resin composition comprises a thermoplastic resin, a thermosetting resin, an aramid resin, a rubber, or a mixture thereof, and 10 to 70 vol% of the particles. Also, a method for producing the particles is described herein.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of a thermally conductive particle according to the invention; Fig.
2 is a schematic view of an apparatus for measuring the volume resistivity of thermally conductive particles.
3 is a top view photograph of a molded article comprising the thermally conductive particles according to the claims.
4 is a cross-sectional photograph of a molded article comprising the thermally conductive particles of the claimed invention.

The following definitions and abbreviations will be discussed herein and will be used to interpret the meaning of the terms in the claims.

Justice

As used herein, the term "volume resistivity" refers to the electrical resistivity of a material and determines the electrical insulation performance of the material. Volumetric resistivity is measured by inserting sample carbon particles in a transparent cylinder between two electrodes with terminals. In the examples herein, a voltage of 500 V was applied through the terminals to measure the resistivity of the particles described herein.

As used herein, the term "aspect ratio" of a particle refers to the ratio of the maximum length of the particle to its width divided by its maximum thickness.

As used herein, the term "composite core" refers to thermally conductive core particles bound by an organic binder by a mechanofusion process.

As used herein, the terms "thermally conductive" or "thermal conductivity" (often denoted k , lambda , or k ) refer to the physical properties of the material that conducts or transfers heat. Heat transfer occurs at a higher rate across the material of lower thermal conductivity across the material of higher thermal conductivity. Accordingly, a material having a high thermal conductivity is widely used for a heat sink application, and a material having a low thermal conductivity is used as a heat insulating material. Thermal conductivity is typically measured as thermal conductance, which means that when the opposite sides of a plate with a certain area and thickness are different in temperature by 1 K (Kelvin) Refers to the calories passed through. For plates with a thermal conductivity k, area A and thickness L, the calculated thermal conductance is kA / L and is measured in W / m 占 되고 and is equivalent to W / 占 폚.

여기서As used herein, the term "thermal diffusivity" refers to a value obtained by dividing the thermal conductivity of an article by the density and specific heat capacity of the article at a certain pressure, and in contrast to the ability of the article to store thermal energy, Measure the ability to evangelize. It has an SI unit of m2 / s. Thermal diffusivity is denoted the normal α. The expression is:

here

k is the thermal conductivity (W / (mK));

rho is the density (kg / m3);

c _p is the specific heat capacity (J / (kg · K)).

Abbreviation

As used herein, "%" refers to percent.

As used herein, "weight%" refers to weight percent.

As used herein, "volume%" refers to volume percent.

As used herein, "hr" refers to time; "m" refers to minutes; "s" refers to seconds.

As used herein, "g" refers to grams.

As used herein, "μm" refers to a micrometer.

As used herein, "nm" refers to nanometers.

As used herein, "rpm" refers to the number of revolutions per minute.

As used herein, "mm" refers to millimeters.

As used herein, "cm" refers to centimeters.

As used herein, "ml" refers to milliliters.

As used herein, "V" refers to a bolt.

As used herein, "? Cm" refers to ohm centimeters.

As used herein, "W" refers to watts.

As used herein, "m" refers to a meter.

As used herein, "K" refers to Kelvin.

As used herein, "mPa s" refers to millipascal seconds.

range

Any ranges described herein explicitly include their endpoints unless explicitly stated otherwise. When describing an amount, concentration, or other value or parameter as a range, it specifically discloses all ranges formed from any pair of any range upper limit and any range lower limit, Whether or not it is. The processes and articles described herein are not limited to the specific values disclosed therein for defining the scope in the description.

Preferred variant

The disclosure of this specification with respect to any modifications in terms of the processes, compositions and articles described herein, whether material, method, step, value, and / or range, such as those identified as preferred variants, , Steps, values, ranges, and the like, unless the context clearly dictates otherwise. It is intended that any such disclosed combination be a preferred variation of the processes, compositions, and articles described herein, with the aim of providing a very real and sufficient backing for the claims.

Generally

Thermally conductive particles are described herein and one of which is shown as element 10 in Figure 1 wherein the element 10 is a composite of core particles 11 joined together by an organic binder 12, core; And an insulating material 13 at least partially coating the composite core.

Also disclosed herein are the thermoconductive particles and thermoplastic resins, thermosetting resins, aramid resins, rubbers, or resin compositions comprising mixtures thereof, as described herein.

A method of at least partially coating a composite core with an insulating material is also described herein,

The composite core comprises a plurality of core particles and an organic binder that binds the core particles together,

The core particles are thermally conductive and selected from the group consisting of metal particles, ceramic particles, carbon-based particles, and mixtures thereof,

The insulating material is selected from the group consisting of sericite, boehmite, talc, and mixtures thereof,

The thermally conductive particles have a volume resistivity in the range of at least 1 x 10 < ⁴ > OMEGA .cm to 1 x ¹⁰ < 10 > OMEGA .cm as measured for the cylinders of thermally conductive particles having a diameter of 10 mm and a height of 3.0 mm at a voltage of 500 V .

Thermally conductive particles

Composite cores are produced by combining a plurality of core particles with an organic binder using a compression shear mixing method, which can be made to have a desired particle size or shape. The volume of organic binder per 100 parts by volume of core particles is in the range of 1 to 30 parts skin, preferably 2 to 26 parts skin, and more preferably 4 to 22 parts skin.

The composite core is partially or wholly coated with an insulating layer, wherein the thickness of the insulating layer is in the range of 0.1 to 10 [mu] m, and preferably 0.5 to 6 [mu] m. The volume of the insulating material per 100 parts by volume of the composite core is in the range of 3 to 48 parts, preferably 5 to 35 parts, and more preferably 10 to 32 parts. Such a volumetric concentration of the insulating material and the thickness of the insulating coating impart sufficient thermal conductivity to the thermally conductive particles and the desired volume resistivity described in the claims.

The average particle size of the thermally conductive particles described herein ranges from 0.5 to 300 μm, preferably from 20 to 250 μm, and more preferably from 90 to 190 μm. The average particle size can be determined by measuring its longest axis 14 through scanning electron microscopy (SEA).

The aspect ratio of the thermally conductive particles described herein ranges from 1 to 100, preferably from 2 to 50, more preferably from 3 to 35, and even more preferably from 4 to 15. [ Figure 1 shows the aspect ratio as a value obtained by dividing the particle length (along the long axis 14) by the particle thickness 15. The aspect ratio of the thermally conductive particles described herein is preferably greater than 2, and is preferably in the range of from 3 to about 7. When the thermally conductive particles have a flat shape, if they are molded into an article together with the resin, an anisotropic thermal conductivity can be provided to the molded article.

The volume resistivity of the thermally conductive particles as disclosed herein is at least 1 × 10 Ω · in the range of cm Ω · cm, preferably 1.0 × 10 ⁴ to 1.0 × 10 ¹⁸ Ω · cm, more preferably from 1.0 × 10 ⁴ to in the range of 1.0 × ¹⁰ 10 Ω · cm.

In any of the thermally conductive particles, compositions, or methods described herein, any of or all of the following elements may be combined to produce a wide variety of variations, each of which is considered as the described invention:

- The core particles can be carbon-based particles and / or;

- The carbon-based particles are graphite and / or;

- The core particles are / are naturally occurring graphite and flaky carbon-based particles in a ratio of 3: 2 to 99: 1;

- When a mixture of graphite and flaked carbon-based particles is used, the flaked carbon-based particles have an average thickness smaller / smaller than the average thickness of the naturally occurring graphite;

- The core particles are 100 parts skin of the thermally conductive particles described herein;

- The organic binder is in the range of 3 to 25 parts skin of the volume of core particles and / or;

- The insulating material is in the range of 4 to 48 parts skin of the core particles and / or;

- The organic binder is a thermosetting resin and / or;

- The average particle size of the thermally conductive particles described herein ranges from 0.5 [mu] m to 300 [mu] m and / or;

- The insulating material is selected from the group consisting of sericite, boehmite, talc, mica, and mixtures thereof;

- In the thermally conductive resin composition described in this specification, the thermally conductive particles are in the range of 10 to 70% by volume of the total volume of the composition and / or;

- The thermally conductive resin composition may include a thermoplastic resin, a thermosetting resin, an aramid resin, a rubber, or a mixture thereof.

a) Composite core

The composite core exhibits a sufficient thermal conductivity of 100 W m ^-1 K ^-1 or more and preferably 800 W m ^-1 K ^-1 or less. The maximum value is generated for a composite core having an anisotropic thermal conductivity.

Core particles

The composite core may comprise core particles of metal, ceramic, or carbon or mixtures thereof. The metal particles include copper, silver, nickel, aluminum, or an alloy thereof. The ceramic particles include aluminum nitride, silicon carbide, and alumina. The carbon-based particles include graphite, carbon nanotubes, fullerene, graphene, carbon black, glassy carbon, carbon fiber, amorphous carbon, boron carbide, or a mixture thereof.

Preferably, the composite cores comprise carbon-based particles. The carbon-based particles preferably include graphite, and graphite may be natural or synthetic, and natural graphite is preferred due to its thermal conductivity and cost.

In particular, the carbon-based particles include graphite blends of platy graphite, also known as flake, as well as somewhat spherical graphite, which have spherical graphite to flake graphite in a ratio of 3: 2 to 99: 1 By volume, and preferably in a volume ratio of 1: 1 to 6: 1. Flaked carbon-based particles thinner than natural graphite include expanded graphite, graphene, and mixtures thereof. Expanded graphite is a flake natural graphite in which graphite is expanded and separated in the direction in which the interlayer spaces are expanded by chemical treatment and heat treatment so that the layers are laminated. Graphene is a flake phase particle whose carbon atoms are arranged in hexagonal lattices. T is a few μm thick for natural graphite and less than 1 μm thick for expanded graphite and graphene.

By mixing relatively thick natural graphite with flaked carbon-based particles, a somewhat flat thermally conductive composite core is formed. Molded articles formed from a resin composition comprising somewhat flat thermally conductive particles impart an anisotropic path of heat conduction, which increases the thermal conductivity of the shaped article.

The average particle size of the composite core ranges from 1 to 150 μm, preferably from 15 to 100 μm, and more preferably from 30 to 90 μm. The average particle size of the composite core is determined by measuring the longest axis of the composite core by scanning electron microscopy (SEM).

The aspect ratio of the composite core is preferably at least 1, more preferably at least 2, and even more preferably at least 5. The composite core may include two or more types of particles having different aspect ratios.

Organic binder

The composite core may be formed into a desired shape by bonding one or more core particles together with an organic binder. The organic binder is a polymer having a weight average molecular weight of 300 or more. The weight average molecular weight is preferably less than 1,000,000.

The type of organic binder is not particularly limited, but is preferably a thermoplastic resin, a thermosetting resin, or a mixture thereof, more preferably a thermosetting resin. The thermosetting resin may be at least one selected from the group consisting of epoxy, novolac, isothiocyanate, melamine, urea, imide, aromatic polycarbodiimide, phenoxy resin, phenol, methacrylate, unsaturated polyester, vinyl ester, ureaurethane, Silicon, and mixtures thereof. The thermosetting resin is preferably melamine.

The organic binder may be in solution or may be dispersed in a solvent. A preferred solvent is water; An organic binder aqueous solution is preferred.

Manufacture of composite core

The composite core can be formed by mixing the core particles with the organic binder and bonding and mixing the core particles with the organic binder. The organic binder is filled in the gap between the core particles and increases the mechanical strength of the core particles.

Compression shear mixing can be used to bond the core particles by blending the core particles with the organic binder. Compressive shear mixing is a method of applying a compressive force and a shearing force to a plurality of particles (mixture of core particles and organic binder) of different materials so that the particles are bonded to each other.

A Mechanofusion System (Hosokawa Micron Ltd.) or Theta Composer System (Tokuju Corp.) can be used to provide compression shear mixing. When a mechanofusion system is used, a rotating blade inside a compression vessel presses the core particles and the organic binder against the inner wall of the vessel and provides strong compressive and shear forces to couple and mix the core particles with the organic binder do.

When used in the dry particle composite machine, for example, NOB-130 ^® (Hosokawa Micron available from limited available) is bonded, and the gap between the blade and the vessel wall is in a range of 1 to 3 mm, the rotational speed of the blade is preferably 1,000 rpm to 6,000 rpm, and more preferably from 1,800 rpm to 4,500 rpm.

When the theta composer system (THC model theta composer available from Tokushu Corporation) is used, the vessel of the system rotates in one direction while the elliptical rotor inside the vessel rotates in the opposite direction and the gap between the vessel wall and the rotor Compression and shearing are applied within the core to bond the core particles with the organic binder. The gap between the rotor and vessel wall is in the range of 1 to 3 mm, and the rotational speed of the blade is preferably in the range of 1,000 rpm to 6,000 rpm, and more preferably in the range of 1,800 rpm to 4,500 rpm.

The organic binder may also be diluted beforehand with the solvent, before mixing with the core particles. By diluting the organic binder with a solvent, carbon particles can be combined with fewer binders. The solvent may be of any type as long as the solvent dissolves the organic binder. The solvent may be water, isopropyl alcohol (IPA), methanol, ethanol, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate Ethanol amine (MEA), dipropylene glycol diacrylate (DPGDA), or mixtures thereof. The solvent is preferably a solution in which the organic binder is uniformly dispersed. When the organic binder is water-soluble, the solvent is preferably water.

The mixing temperature of the core particles and the organic binder is not particularly limited, but depends on the type and viscosity of the organic binder. In particular, when the organic binder is an aqueous solution, the mixing temperature is preferably in the range of from 10 캜 to less than 80 캜, and more preferably from 25 캜 to less than 50 캜 to avoid evaporation of water.

The viscosity of the organic binder or mixture of organic binder and solvent is preferably in the range of 0.5 to 1,000 mPa · s at 20 ° C. The composite core can achieve the desired shape by adjusting the viscosity of the organic binder and solvent during mixing. The composite core is somewhat flat at 0.5 to 100 mPa · s at 20 ° C and more spherical at 100 to 1,000 mPa · s.

The mixing time can be adjusted so that the core particles and the organic binder are properly combined and mixed with each other. The mixing time is preferably in the range of 1 minute to 30 minutes, and more preferably in the range of 3 minutes to 10 minutes.

b) Insulating material

The insulating material of the thermally conductive particles described in this specification has a volume resistivity of 1 x 10 < ⁹ > OMEGA .cm or more and preferably 1 x 10 < ²² > Suitable insulating materials are not particularly limited and may be naturally occurring or synthetic and include, without limitation, metal oxides, metal carbonates, carbonate minerals, metal nitrides, metal sulfides, phosphate minerals, clay minerals, silicate minerals, .

The metal oxide is aluminum oxide (Al ₂ O _3), zinc (ZnO), titanium oxide (TiO _2), iron oxide (FeO), magnesium oxide (MgO), silicon oxide (SiO _2), boehmite (Al ₂ O ₃ H ₂ O), or mixtures thereof. Metal carbonates include calcium carbonate (CaCO _3), magnesium carbonate (MgCO _3), or a mixture thereof. Carbonate minerals include calcite (polymorphic CaCO ₃ ), aragonite (crystalline CaCO ₃ ), dolomite (CaMg (CO ₃ ) ₂ ), hydrotalcite (Mg ₆ Al ₂ CO ₃ (OH) ₁₆ · 4 (H ₂ O) ), fatigue Au Added _{(Mg 6 Fe 2 (CO 3} ) (OH) 16 · 4 (H 2 O)), mana three children agent _{(Mg 6 Al 2 (CO 3} ) (OH) 16 · 4H 2 O), Or mixtures thereof. The metal nitride includes boron nitride (BN), aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), or a mixture thereof. The metal sulfides include molybdenum sulfide (MoS ₂ ), tungsten sulfide (WS ₂ ), zinc sulfide (ZnS), or mixtures thereof. Phosphate minerals include apatite (Ca ₅ (PO ₄ ) ₃ (F, Cl, OH)), hydroxyapatite (Ca ₅ (PO ₄ ) ₃ (OH)), or mixtures thereof. The silicate minerals include monoclinic crystalline clay minerals such as sericite ((Mg, Fe) ₃ Si ₂ O ₅ (OH) ₄ ), pyrophyllite (Al ₂ Si ₄ O ₁₀ (OH) ₂ ), kaolin clay, (KAl ₂ AlSi ₃ O ₁₀ (OH) ₂ ), montmorillonite ((Na, Ca) _0.33 (Al, Mg) ₂ Si ₄ O ₁₀ (OH) ₂ .nH ₂ O), chlorite minerals, talc, and smectite group minerals), include mica, diatomite _{(SiO 2 · nH 2 O)} , or mixtures thereof.

Since the formulas of the insulating materials listed above can be applied to the classes of insulating material, any paper of insulating material identified by the formula is contemplated in the thermally conductive particles described herein.

Suitable insulating materials include aluminum oxide (alumina), zinc oxide, talc, magnesium oxide, silicon dioxide, boehmite, boron nitride, mica, aluminum nitride, silicon nitride, zinc sulphide, or mixtures thereof. More preferred insulating materials include talc, boehmite, sericite, mica, or mixtures thereof. Talc is particularly preferred.

The average particle size of the insulating material is preferably 10 nm to 50 占 퐉, more preferably 100 nm to 30 占 퐉, and still more preferably 300 nm to 15 占 퐉.

The volume concentration of the insulating material relative to the thermally conductive core particles is from about 4 to about 40% by volume, preferably from about 5 to about 30% by volume, more preferably from about 8 to about 30% by volume, and most preferably from about 10 To about 25% by volume.

Coating of composite core by insulating material

The composite core is at least partially coated with an insulating material, which preferably has a volume resistivity of 1 x 10 < ⁹ > to 1 x 10 < ²⁰ >

Similar to forming a composite core, a mechanofusion system or a theta composer system can be used to coat the composite core with an insulating material, wherein the insulation material is intrinsically fused to the surface of the composite core by compressive and shear forces. Alternatively, different methods can be used to coat the composite core. However, in order to maximize manufacturing efficiency, it is desirable to form a composite core using the same system and coat it with an insulating material. Preferably, a mechanofusion process is used to form and coat the composite core.

In this process, the core particles and the organic binder are first subjected to compression shear mixing to form a composite core, to which an insulating material is added, which is then subjected to compression shearing mixing to form a composite core Thermally conductive particles are produced. The temperature at which the composite core is coated with the insulating material is preferably in the range below the curing temperature of the organic binder, and in the case where the solvent is used, it is in the range below the boiling point of the solvent. The coating temperature is preferably in the range of from 10 캜 to less than 80 캜, and more preferably from 25 캜 to less than 50 캜. The insulating material will at least partially coat the surface of the composite core, thereby creating the thermally conductive particles described herein.

In addition, the duration of the compressive shear mixing of the composite core and the insulating material can be adjusted to fuse the insulating material to the surface of the composite core, preferably in the range of 5 seconds to 5 minutes, and more preferably 10 seconds to 120 seconds .

The insulating material preferably covers or covers the entire surface of the composite core. Alternatively, the insulating material may cover or coat a portion of the surface of the composite core sufficient to maintain the volume resistivity of the thermally conductive particles above 1 x 10 < ⁴ >

Resin composition

The composition described herein comprises the thermally conductive particles described herein dispersed in a thermoplastic resin, a thermoset resin, an aramid resin, a rubber, or a mixture thereof. The compositions described herein exhibit both thermal conductivity and volume resistivity sufficient for use in molded articles, films, sheets, adhesives, and the like. For example, the compositions described herein may be manufactured as an insulating film and applied to the surface of an electronic component, or may be injection molded and used as a housing for a heat generating electronic component such as an LED bulb component or the like.

In the case of thermoplastic resins, any suitable resin may be used in the compositions described herein, including polyolefin resins such as polyethylene and polypropylene, polyamide resins such as nylon 6, nylon 66, nylon 610, nylon 12, and aromatic polyamides , Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polycyclohexylmethylene terephthalate, cyclic polyester oligomers, ABS resins, polycarbonate resins, modified polyphenylene ether resins, polyacetal resins, poly A phenylene sulfide resin, a wholly aromatic polyester resin, a polyether ether ketone resin, a polyether sulfone resin, a polysulfone resin, and a polyamide-imide resin. Copolymers obtained by selectively blending the components constituting these resins may also be used. Thermoplastic resins may be blended. Preferably, the thermoplastic resin is selected from the group consisting of a polyamide resin, a polyester resin, a polyphenylene sulfide resin and a wholly aromatic polyester resin.

In the case of thermosetting resins, any suitable resin may be used in the compositions described herein, and may be an epoxy resin, a novolak resin, an isothiocyanate resin, a melamine resin, a urea resin, an imide resin, , A phenoxy resin, a phenol resin, a methacrylate resin, an unsaturated polyester resin, a vinyl ester resin, a urea urethane resin, and a resol resin. Preferably, the thermosetting resin contains a melamine resin, an epoxy resin, or an unsaturated polyester resin.

Any suitable solvent may be added to the composition described herein so long as it dissolves the resin or rubber or adjusts its viscosity. Most of the solvent is expected to evaporate at the drying stage. Suitable solvents include water, isopropyl alcohol (IPA), methanol, ethanol, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA) Monoethanolamine (MEA), dipropylene glycol diacrylate (DPGDA), or mixtures thereof.

The volume of the thermally conductive particles described herein relative to the total volume of the composition described herein is preferably 10 to 70% by volume, more preferably 15 to 50% by volume, and even more preferably 20 to 38% . When the volume percent of the thermally conductive particles relative to the total volume of the composition is within these ranges, sufficient thermal conductivity and volume resistivity will be obtained.

The compositions described herein may contain additives such as antioxidants, glass fibers, and lubricants.

The volume resistivity of an article made from the composition described herein is preferably 1.0 x 10 ¹⁰ to 1.0 x 10 ¹⁸ Ω · cm, more preferably 1.0 x 10 ¹³ to 1.0 x 10 ¹⁵ Ω · cm. The thermal conductivity of the surface of a 1 mm thick molded article made from the compositions described herein is preferably from 0.5 W / mK to 10.0 W / mK and more preferably from 1.0 W / 5.0 W / mK or less.

The method for producing thermally conductive particles described in this specification

The thermally conductive particles described herein exhibit the volume resistivity described because of the process in which it is made, i.e. because of the following two-step process:

First, as shown in Fig. 1, a composite core is prepared by bonding together thermoconductive core particles and an organic binder, and then the composite core is at least partially coated with an insulating material. Both steps - producing the composite core and coating the composite core - are performed by compression shear mixing.

In particular, the thermally conductive particles described herein are prepared by the following steps:

First, a dry particle composite apparatus, for example, NOB-130 ^® (available from Hosokawa Micron, Ltd.) in a rotation speed of 3,000 rpm 5 bun both compresses the heat-conductive core particles and the organic binder as described herein for Shear mixing to form a composite core; And

The step of compression shearing mixing the composite core and the insulating material in the dry particle hybridization apparatus such that the surface of the composite core is at least partially coated with the insulating material to form thermally conductive particles.

The duration of the first compression shear mixing may range from about 30 seconds to about 90 minutes; The organic binder may be dissolved or suspended in a solvent, preferably water, to prepare an organic binder solution or suspension. The second shear mixing time may range from 30 seconds to less than about 10 minutes.

Preferably, these particles can then be heat treated at 120 DEG C for 3 hours to remove moisture. If the organic binder is a thermosetting resin such as methylol melamine, the resin may cause further crosslinking by heat treatment.

The thermally conductive particles may then be made into a thermally conductive resin composition added to any suitable resin or polymer as described herein.

Example

The present invention is exemplified by the following Example (E) and Comparative Example (C), but is not limited thereto.

material

- Natural graphite particles - Flake graphite having an average particle size of 60 占 퐉 available as graphite X-100 from ITO Graphite Co. Ltd.

- Methylol melamine (MM) - An organic binder available from Nikon Carbide Industries Co. Inc. as Nikaresin S-176.

- Aqueous Polyester (PE) - Water soluble polyester available from Goo Chemical as Z730.

- Polyamide (PA) - polyamide suspension in water available from Sumitomo Seika Chemicals as PA200.

- Sodium polystyrene sulfonate (SPS) - 20% aqueous solution of sodium polystyrene sulfonate available from PSO 50 from Tosoh Organic Chemical.

- Talc 1 - average D50 The particle size is 0.65 μm and available as HTP Ultra 5 from IMI FABI Co., Ltd.

- Talc 2 - average D50 particle size of 2.4 μm, available from HIP 2C from IM AVI Fabry Company Limited.

- Talc 3 - average D50 particle size of 5 μm, available from Fuji Talc Industrial as LMS200.

- Sericite-fine grain mica, average D50 particle size of 1.6 占 퐉 and available from Serine Site J from Kinsei Matic, Co. Ltd.

- Mica-average D50 particle size of 5 μm, available from Yamaguchi Mica.

- Boehmite-average D50 particle size of 3 to 5 [mu] m and available as BMF from Kawai Line Industry.

- titanium dioxide (TiO ₂₎ - D50 and the average particle size exceeds 0.5 μm, of Wilmington, Delaware, USA Will this material. children. DuPont de four together & Company (EI du Pont de Nemours and Company ) to obtain pure Ti (Tipure) ^® R108 available from [DuPont (DuPont)].

- Boron Nitride (BN) - average D50 particle size of 12 μm, available as SGP from Denki Kagaku.

- Calcium hypobromite (CaF ₂ ) - average D50 particle size of 6 μm, available from Sankyo Seifun as HO # 100.

- Expanded graphite - obtained from Ito Kokuen Co., Ltd., EC300.

- a polybutylene terephthalate (PBT) - available ^® Klein sustaining (Crastin) available from DuPont.

Way

Measurement of volume resistivity

The volume resistivity of the thermally conductive particles in the examples and comparative examples was measured by the two-terminal method using the device 20 in Fig. A transparent cylinder 22 having a 10 mm inner diameter connected to the terminal electrode 21 at two positions on both sides was filled with graphite particles 23 to a height of 3.0 mm. The charge amount was 0.2 g. The surface area of one of the terminal electrodes 21 in contact with the transparent cylinder 22 was 0.785 cm 2. Volumetric resistivity was obtained by applying a 500 V voltage to the cylinder between the two terminals.

Methods of making the thermally conductive particles described herein

All examples of the thermally conductive particles described in the following table were prepared using Method A. Comparative Example C1 was prepared using Method B, and Comparative Example C2 was prepared using Method B.

Method A: Two compression shear mixing steps to produce thermally conductive particles

The first step was compression shear mixing of graphite and organic binder to produce composite core, and the second step was compressive shear mixing of composite core and insulation material.

Natural graphite particles and an organic binder were added into a dry particle hybridization device (NOB-130 ^® , available from Hosokawa Micron Limited) and compression shear mixed at a rotation speed of 3,000 rpm for 5 minutes to form a composite core. The organic binder in the table is obtained by dissolving or suspending a specific binder in a large amount of water to be used as a solvent to produce an organic binder solution or suspension.

Insulating materials including talc, boehmite, sericite, and mica were then added to the dry particle hybridization apparatus containing the composite core and subjected to a second compression shear mixing for 30 seconds at a rotation speed of 3,000 rpm to form a composite And partially formed on the surface of the core to produce thermally conductive particles. The thermally conductive particles were heat-treated at 120 DEG C for 3 hours to remove the remaining solvent. When methylol melamine was used as the organic binder, methylol melamine was further crosslinked by the heating step.

Method B: Single Compression Shear Mixing Step: Premix mixing of the organic binder and the insulating material, then adding the thermally conductive core particles, followed by compression shearing mixing of all elements

The talc and methylol melamine aqueous solutions were premixed together to form a talc / methylol amine mixture. This premixing was not a compression shear step. The premix was then added to the dry particle hybridization apparatus as described in Method A with natural graphite particles and compression shear mixed for 5 minutes to form the thermally conductive particles. The thermally conductive particles were heat-treated at 120 ° C for 3 hours to remove the solvent, and thermally conductive particles having a volume resistivity of 8 × 10 ² Ω · cm were produced at a voltage of 500 V.

This method uses only one compression shear mixing step. Thus, in Method B, a composite core was not created first.

Method C: Single Compression Shear Mixing Step: Mixing the organic binder, thermoconductive core particles and insulating material together by compression shearing

This method has no preliminary mixing step, and all the elements are added together and compression shear mixed. The natural graphite particles, the organic binder (melamine aqueous solution) and the insulating material (talc) were added together in a dry particle hybridization apparatus as described in Method A and compression shear mixed for 5 minutes to form thermally conductive particles. Then, the thermally conductive particles were heat-treated at 120 ° C for 3 hours to remove the solvent, thereby producing thermally conductive particles having a volume resistivity of 8 × 10 ³ Ω · cm at a voltage of 500 V. Similar to Method B, Method C also uses only one compression shear step and does not create a composite core.

result

[Table 1]

Table 1 compares the volume resistivity of the thermally conductive particles produced by mechanofusion processes A, B, and C with the same rotational speed, curing temperature and duration. E1 was prepared by the mechanofusion process A and the mechanofusion process A achieved the described volume resistivity thermally conductive particles while the mechanofusion process B or C achieved C2 and C3, Volume resistivity.

[Table 2]

All examples and comparative examples in Table 2 were prepared by Method A and provided an aspect ratio of 5.85, with an average length along the major axis of 131.7 μm and an average thickness of 22.5 μm. Each of E2 to E5 had different amounts of organic binder in the composite core. C3 had no organic binder and had a volume resistivity of 5 Ω · cm. This is in contrast to the minimum volume resistivity of E2 to E5 of 1.5 x 10 < ⁷ > Table 2 shows that when the volume percentage of the organic binder with respect to the amount of thermally conductive core particles is in the range of 3 to 20, a volume resistivity described above of 1 x 10 ⁴ ? · Cm or more is obtained.

Table 2 also shows thermally conductive particles, E6, having two types of graphite in a composite core, formed in the same manner as in E2, except that 20 parts of natural graphite 100 parts skin was replaced with expanded graphite . The volume resistivity of E6 was 5.5 × 10 ⁵ Ω · cm, which was almost five times better than the volume resistivity of E2.

[Table 3]

The examples in Table 3 were formed in the same manner as the example in Table 2, except that the amount of insulating material was varied. E7 to E10 each had a different amount of insulating material, i.e., talc. C4 lacked talc. The volume resistivities of C4 and E7 to E10 were measured as for Examples 2 to 6.

Table 3 shows that the volume resistivity of E7 to E10 increases as the amount of talc increases. The volume resistivity of E10, which contains twice the amount of talc as in E9, was equal to the volume resistivity of E9. These results show that a relatively more effective amount of insulating material ranges from about 10 to about 20 parts skin of the total volume of thermally conductive particles.

[Table 4]

The thermally conductive particles in Table 4 were formed in the same manner as in Examples 2 to 10 except that the average particle size of the talc insulating material was varied. E11 had talc particles of about the same average size as in E9. E11, E12, and E13 had average particle size talc of 650 nm, 2.4 μm, and 5.0 5.0 μm, respectively. Thus, the average talc particle size for E12 was about four times larger than the average talc particle size for E11 (E9). The average talc particle size for E13 was about twice the mean talc particle size for E12 and about 8 times larger than the average talc particle size for E11 (E8). The volume resistivities of E11 (E9) and E12 were virtually similar, regardless of the difference in the average insulating particle size four times. However, a decrease in the volume resistivity of E13 relative to the volume resistivity of E12 implies that when the talc is an insulating material, optimal results are achieved when the average talc particle size is in the range of 600 nm to about 3.0 μm. Nevertheless, in all three embodiments, E11 to E13, the volume resistivity of the thermally conductive particles was greater than 1.0 x 10 < ⁸ > [Omega] cm, which is a 10,000-fold increased value compared to the minimum listed.

[Table 5]

In Table 5, C5, C6, and C7, respectively having titanium dioxide, boron nitride, and calcium fluoride as insulating materials, failed to achieve thermally conductive particles having the volume resistivity described. Calcium fluoride has a Mohs hardness of 4.0; Boron nitride has a particle size of about 12 [mu] m; Titanium oxide in C5 had a spherical shape with an aspect ratio of about 1.

In contrast, Table 5 shows that E14, E15, and E16, each having sericite, mica, and boehmite as insulating materials, achieved respective thermally conductive particles having a volume resistivity of 1.0 x 10 ⁴ or more. Both boehmite, sericite, and mica have a Mohs hardness value of less than 3.5 and a particle size of about 5 탆 or less.

[Table 6]

Table 6 shows the volume resistivity of thermally conductive particles with different organic binders. Each of the organic binders used in Table 6 produced thermally conductive particles having a volume resistivity of 1 x 10 < ⁴ > The use of methylol melamine or aqueous polyester as the organic binder resulted in thermally conductive particles having the best volume resistivity.

[Table 7]

Table 7 shows a resin composition in which thermally conductive particles are dispersed in a resin and a resin composition in which an article is formed by injection molding.

A resin composition as described herein was prepared as follows:

67 parts of skin polybutylene terephthalate resin (of the total volume of the resin composition) and 7 parts of skin polyester elastomer were mixed at 290 占 폚 using a MC15 micromixer manufactured by DSM Xplore Min. The thermally conductive particles from E10 were added to 26 parts of skin (of the total volume of the resin composition) and stirred at 290 DEG C for an additional 30 seconds to produce a resin composition.

The resin composition was injection molded at a mold temperature of 125 캜 to produce molded articles of 21 mm length, 16 mm width, and 1 mm thickness (Fig. 3). By using an ohmmeter (Hiresta-UP manufactured by Mitsubishi Chemical Corp.), the volume resistivity at the surface of the molded article was 1.0 × 10 ¹⁴ Ω · cm or more Respectively. In addition, the thermal diffusivity of the molded article in the direction of injection of the molded article was measured by means of a laser flash method using a Bruker AXS model LFA 447 NanoFlash ^® in an area of 15 mm x 15 mm, And the heat diffusivity was found to be 1.4 W / mK, as calculated by the specific heat and density.

When the cross section of this molded article was observed with an electron microscope, thermally conductive particles containing the graphite-containing composite material 41 and the insulating layer 42 coating the surface thereof were observed as shown in Fig. In addition, the thermally conductive particles were aligned in the resin 43 almost in parallel.

Claims (15)

As thermally conductive particles,
Composite core; And
An insulating layer,
The composite core comprises a plurality of core particles and an organic binder that binds the core particles together,
The core particles are thermally conductive and selected from the group consisting of metal particles, ceramic particles, carbon-based particles, and mixtures thereof,
The insulating material may coat at least a portion of the composite core,
The thermally conductive particles have a volume resistivity in the range of at least 1 x 10 < ⁴ > OMEGA .cm to 1 x ¹⁰ < 10 > OMEGA .cm as measured for the cylinders of thermally conductive particles having a diameter of 10 mm and a height of 3.0 mm at a voltage of 500 V Of the thermally conductive particles. The thermally conductive particles of claim 1, wherein the core particles are carbon-based particles. The thermally conductive particles according to claim 1, wherein the carbon-based particles are graphite. 3. The method according to claim 1 or 2,
The core particles are naturally occurring graphite and flaky carbon-based particles in a 3: 2 to 99: 1 ratio,
The flaked carbon-based particles are thermally conductive particles whose average thickness is less than the average thickness of naturally occurring graphite. 3. The method according to claim 1 or 2,
The core particles are 100 parts skin,
Wherein the organic binder is in the range of 3 to 25 parts skin of the core particles and the insulating material is in the range of 4 to 48 parts skin of the core particles. 6. The method of claim 5,
The core particles are naturally occurring graphite and flaked carbon-based particles in a 3: 2 to 99: 1 ratio,
The flaked carbon-based particles are thermally conductive particles whose average thickness is less than the average thickness of naturally occurring graphite. 3. The method according to claim 1 or 2,
The organic binder is a thermosetting resin. The method according to claim 6,
The organic binder is a thermosetting resin. 3. The method according to claim 1 or 2,
Wherein the average particle size of the thermally conductive particles is in the range of 0.5 mu m to 300 mu m. 9. The method of claim 8,
Wherein the average particle size of the thermally conductive particles is in the range of 0.5 mu m to 300 mu m. 3. The method according to claim 1 or 2,
Wherein the insulating material is selected from the group consisting of sericite, boehmite, talc, mica, and mixtures thereof. 11. The thermally conductive particles of claim 10, wherein the insulating material is selected from the group consisting of sericite, boehmite, talc, mica, and mixtures thereof. As a method for producing thermally conductive particles,
At least partially coating the composite core with an insulating material,
The composite core comprises a plurality of core particles and an organic binder that binds the core particles together,
The core particles are thermally conductive and selected from the group consisting of metal particles, ceramic particles, carbon-based particles, and mixtures thereof,
The insulating material is selected from the group consisting of sericite, boehmite, talc, mica, and mixtures thereof,
The thermally conductive particles have a volume resistivity in the range of at least 1 x 10 < ⁴ > OMEGA .cm to 1 x ¹⁰ < 10 > OMEGA .cm as measured for the cylinders of thermally conductive particles having a diameter of 10 mm and a height of 3.0 mm at a voltage of 500 V Lt; / RTI > 14. The method of claim 13,
Wherein the composite core is formed by applying a compressive force and a shear force so that the core particles are mixed with the organic binder. As the resin composition,
Thermally conductive particles, and
A resin selected from the group consisting of:
The thermally conductive particles comprise a composite core and an insulating layer,
The composite core comprises a plurality of core particles and an organic binder that binds the core particles together,
The core particles are thermally conductive and selected from the group consisting of metal particles, ceramic particles, carbon-based particles, and mixtures thereof,
The insulating material may coat at least a portion of the composite core,
The thermally conductive particles have a volume resistivity in the range of at least 1 x 10 < ⁴ > OMEGA .cm to 1 x ¹⁰ < 10 > OMEGA .cm as measured for the cylinders of thermally conductive particles having a diameter of 10 mm and a height of 3.0 mm at a voltage of 500 V Lt; / RTI >
Wherein the thermally conductive particles are in a range of 10 to 70% by volume of the total volume of the resin composition.

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