KR20140080115A - Electrically conductive thermoplastic resin composition with excellent thermal conductivity and reduced anisotropy in thermal conductivity - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to an electrically conductive thermoplastic resin composition having excellent thermal conductivity and reduced anisotropy of thermal conductivity, and more particularly, to a thermoplastic resin composition comprising a polyphenylene sulfide resin, graphite, and glass fibers modified with carbon nanotubes, It has excellent physical properties including plasticity and mechanical properties, exhibits reduced anisotropy of thermal conductivity, possesses mass-producibility using a twin-screw extruder, and moldability applicable to an injection process, and thus can be used for automobile interior / exterior materials, And a thermoplastic resin composition that can be usefully applied as a material for lighting parts.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an electrically conductive thermoplastic resin composition having excellent thermal conductivity and reduced anisotropy of thermal conductivity,

TECHNICAL FIELD The present invention relates to an electrically conductive thermoplastic resin composition having excellent thermal conductivity and reduced anisotropy of thermal conductivity, and more particularly, to a thermoplastic resin composition comprising a polyphenylene sulfide resin, graphite, and glass fibers modified with carbon nanotubes, It has excellent physical properties including plasticity and mechanical properties, exhibits reduced anisotropy of thermal conductivity, possesses mass-producibility using a twin-screw extruder, and moldability applicable to an injection process, and thus can be used for automobile interior / exterior materials, And a thermoplastic resin composition that can be usefully applied as a material for lighting parts.

In recent years, there has been an increasing demand for light weight, thin film, and integration depending on the application of resins used as materials for automobiles and electric / electronic parts. Accordingly, there has been a tendency to replace the metal by improving the strength, heat resistance and heat radiation characteristics of the resin composition. The thermoplastic resin exhibits 0.2 to 0.3 W / m · K based on the thermal conductivity, while aluminum, which is a typical example of the high heat dissipating metal, exhibits a high heat radiation property of about 200 W / m · K.

To improve the low thermal conductivity of such resins, many researches on the complexation of thermoplastic resins have been carried out, and a representative method thereof is to combine thermally conductive heat-radiating fillers with thermoplastic resins. As the carbon material, graphite, carbon powder, carbon fine particles, carbon black, carbon fiber, carbon nanotube, carbon nanofiber, carbon nanowire, etc. may be used. And ceramics such as silicon carbide, boron nitride, aluminum nitride, magnesium oxide, diamond, beryllium oxide, boron phosphide, aluminum nitride, beryllium sulfide, boron azide, silicon, gallium nitride, aluminum Phosphide, gallium phosphide, and the like. In some cases, a hybrid material of the carbon material and the ceramic material may be used.

The standard for selecting the above-mentioned heat-radiating filler material is mainly based on the electric conductivity. When the electric conduction characteristic is required and a high thermal conductivity is desired, the carbon-based filler is mainly applied and the electric insulation property is relatively high When an unfavorable thermal conductivity is required, a ceramic filler is mainly applied. Further, it is known that various adjustments of electrical insulation and heat conduction characteristics can be provided by appropriately adjusting the carbon-based filler and the ceramic-based filler.

In order to impart a high degree of thermal conductivity, the following properties are important for the heat-radiating filler: thermal conductivity, shape, aspect ratio (aspect ratio = length / height), true density, bulk density Particularly, the aspect ratio is important because the surface area of the filler increases with an increase in the aspect ratio, thereby improving the heat transfer characteristic.

In addition, in order to exhibit high heat dissipation characteristics, the characteristics of the underlying base resin are also important. Particularly, the thermal conductivity and the crystal structure of the base resin are important. The crystalline resin is more advantageous than the amorphous resin because it exhibits a relatively excellent heat radiation characteristic, and the higher the crystallinity in the crystalline resin, the better the heat radiation characteristic.

In selecting the base resin, the flow characteristics and heat resistance characteristics of the resin are also considered to be very important. The flow characteristics of the resin are related to the impregnation rate of the heat-radiating filler. The higher the fluidity of the base resin, the higher the impregnation than the same filler. In addition, since the heat dissipation material is mainly applied to a region where heat generation is high, a high heat resistance characteristic (i.e., high heat distortion temperature and long-term usable temperature) is basically required depending on the long- A resin which can be easily improved in heat resistance with an increase in crystallinity is preferably used. Examples of the general plastic include polystyrene, polyethylene, and polypropylene. Examples of the engineering plastic include nylon resin (nylon 6, nylon 66, nylon 12 and the like), polyester resin (polybutylene terephthalate, Phthalate and the like), polyarylene oxide based resins such as polyphenylene oxide, and polycarbonate based resins. Examples of super engineering plastics include polyarylene sulfide based resins such as polyphenylene sulfide based resins, A liquid crystal polymer, an aromatic polyamide, a polyarylate, a polysulfone, a polyether sulfone, a polyether imide, a thermotropic liquid crystal polymer resin, and a polyether ketone.

Based on such a base resin, it is advantageous to impregnate a predetermined amount of the filler in a large amount to form a heat conduction path to impart high heat dissipation characteristics. As mentioned above, the shape and density of the heat dissipation filler are advantageously lower. This is because the filler in the heat-dissipating composite material can occupy a high volume fraction. However, such a high volume fraction may cause a high load on the processing equipment during processing, and research on the processing base technology for such processing has been actively conducted.

Japanese Patent Application No. 1996-336364 discloses a resin composition excellent in thermal conductivity and fluidity by high-charging a polyphenylene sulfide resin with? -Alumina. However, since this technique uses a ceramic filler, it exhibits a low heat radiation characteristic with a thermal conductivity of about 3 W / m · K or less, which is difficult to apply to high heat radiation applications.

Japanese Patent Application No. 2000-325377 discloses a composition in which carbon fibers and ceramic fillers are added to polyphenylene sulfide resin to improve thermal conductivity and dimensional stability. However, this technique may exhibit anisotropy of thermal conductivity due to the use of carbon fiber as the main heat sink filler. That is, the carbon fiber has a high thermal conductivity in the longitudinal direction, and a relatively low thermal conductivity in the perpendicular direction, which may cause a difference in thermal conductivity depending on the parts.

Korean Patent Application No. 2007-0027116 discloses a composition in which thermoplastic resin is granulated with carbon fibers and alumina fibers and mixed appropriately to improve the heat conduction characteristics. However, although this technique can solve the anisotropy of thermal conductivity, it is difficult to secure mechanical rigidity and it is difficult to input the raw material by using powdery raw material.

Korean Patent Application No. 2007-0135608 discloses a resin composition comprising a thermoplastic resin mixed with graphite, a ceramic filler, and a fibrous inorganic filler. However, this technique has a disadvantage in that it is difficult to impart high thermal conductivity characteristics because of using a mixture of a carbon-based filler and a ceramic in order to impart an insulating property, and thus it is difficult to apply to parts requiring high thermal conductivity. In addition, there is a disadvantage in terms of material recycling as compared with a single system of a heat-radiating filler.

As described above, attempts have been made to impregnate a thermosetting resin with a heat-radiating filler so as to impart high thermal conductivity and to balance physical properties, but satisfactory results have not yet been obtained.

Disclosure of the Invention The present invention has been made to solve the problems of the prior art described above, and it is an object of the present invention to provide a thermoplastic resin composition having excellent physical properties including thermal conductivity and mechanical properties, exhibiting reduced anisotropy of thermal conductivity, The present invention provides a thermoplastic resin composition which is useful as a material for an automotive interior / exterior material, a housing of an electric / electronic device, and a lighting part.

In order to solve the above technical problems, the present invention provides a method for producing a carbon nanotube, which comprises 10 to 85% by weight of a polyphenylene sulfide resin, 10 to 50% by weight of graphite, and 5 to 40% by weight of glass fibers modified with carbon nanotubes, Conductive, thermoplastic resin composition comprising the thermally conductive, electrically conductive and thermoplastic resin composition.

According to another aspect of the present invention, there is provided a molded article produced by processing the thermally conductive, electrically conductive, and thermoplastic resin composition.

The thermally conductive, electrically conductive, and thermoplastic resin composition according to the present invention has excellent physical properties including thermal conductivity and mechanical properties, exhibits reduced anisotropy of thermal conductivity, and is capable of mass production using a twin-screw extruder and moldability applicable to an injection process . Therefore, the molded article can be usefully used particularly for automobiles (e.g., interior / exterior materials), electrical / electronic products (e.g., housings), or illumination (e.g., LED lights).

Hereinafter, the present invention will be described in detail.

Polyphenylene Sulfide  Suzy

The polyphenylene sulfide resin is typically a resin mainly containing a structural unit represented by the following formula (1). Examples of the method for producing such a polyphenylene sulfide resin include the reaction of a halogen-substituted aromatic compound with an alkali sulfide disclosed in U.S. Patent No. 2513188 and Japanese Patent Publication (Tokukai) No. 44-27671, U.S. Patent No. 3274165 Condensation reaction of thiophenols under air-conditioning such as an alkali catalyst or copper salt, or condensation reaction of an aromatic compound with sulfuric acid under Lewis acid catalyst disclosed in Japanese Patent Publication (Kokoku) No. 46-27255 . Generally, commercially available polyphenylene sulfide resin can be used in the market. There is no particular limitation on the structure, and both linear and cross-linkable types are applicable.

 [Chemical Formula 1]

In the above formula, n is an integer of 10 or more, preferably 20 to 3,000.

The bulk density of the polyphenylene sulfide resin is preferably 0.2 to 1.5 g / cm ³ , and more preferably 0.3 to 1.2 g / cm ³ . If the bulk density of the polyphenylene sulfide resin is less than 0.2 g / cm ³ , it may be difficult to transfer the polyphenylene sulfide resin by a free fall from the constant amount feeder to the feed port of the twin screw extruder. If the bulk density exceeds 1.5 g / cm ³ , Phase separation occurs during agitation with graphite, which has relatively low density, and it may be difficult to make a quantitative feed from a feeder to a feeder of a twin screw extruder.

Further, the melt index (MFR) of the polyphenylene sulfide resin is preferably 10 to 200 g / 10 min, more preferably 50 to 150 g / 10 min at 300 ° C under a load of 1.2 kg. If the flow index of the resin is less than 10 g / 10 min, the workability may be deteriorated. If the flow index exceeds 200 g / 10 min, the mechanical properties of the composition may be rapidly deteriorated.

The polyphenylene sulfide resin is contained in an amount of 10 to 85% by weight, preferably 20 to 75% by weight, and more preferably 20 to 60% by weight within 100% by weight of the resin composition of the present invention. If the content of the polyphenylene sulfide resin in the composition is less than 10% by weight, the flowability of the resin composition is lowered and the extrusion processability becomes difficult to secure. If the content exceeds 85% by weight, the heat dissipation property is difficult to secure.

black smoke

The resin composition of the present invention contains graphite as a heat-radiating filler. Graphite is generally divided into natural graphite and artificial graphite, and has a plate-like structure.

In graphite, graphene forms a continuous plate - like layer, and three electrons formed in planar form have strong covalent bonds, and the remaining one electron is combined with the upper and lower layers. The height of one layer on the hexagonal plate is 3.40 ANGSTROM, and the distance between the closest carbons in the hexagonal ring is 1.42 ANGSTROM. The distance between the upper and lower layers of the platelets is much larger than the center distance of the two carbon atoms (the radius of the carbon atom is 0.77 Å and the carbon ion is tetravalent, 0.16 Å). For this reason, the electrons on the upper side of the hexagonal plate can move somewhat freely, so that graphite has a good electrical conductivity and exhibits a low resistance value of 10 ^-5 Ω · cm based on the volume resistance.

Aspect ratio (length / height) is important for such graphite in the form of plate, because the larger the aspect ratio, the more the heat transfer characteristic is improved due to the increase of the surface area of the filler. In the present invention, the aspect ratio of graphite is preferably 4,000 or more, more preferably 6,000 or more. If the aspect ratio of graphite is less than 4,000, the thermal conductivity characteristics may be degraded due to the reduction of the surface area of the filler.

The fixed carbon content of the graphite is preferably 95% or more, and more preferably 98% or more. The crystallization ratio of graphite is preferably 80% or more, more preferably 90% or more.

The bulk density of graphite is preferably 0.3 to 2 g / cm ³ , more preferably 0.5 to 1.5 g / cm ³ . The bulk density of the graphite 0.3g / cm ³ , It may be too light and bulky to accurately inject into the extruder, and if it exceeds 2 g / cm ³ , the molded product may become heavy and the characteristics of light plastic may not be obtained.

The grain size of the graphite used in the present invention is preferably 10 to 500 mu m, more preferably 100 to 300 mu m. If the particle size of the graphite is too small, there may be a problem that the aspect ratio is reduced and the heat conduction efficiency is lowered. On the other hand, if it is too large, there may be a problem that the surface becomes rough during injection molding. The graphite preferably has a thermal conductivity of 100 W / m · K or more (for example, 100 to 1000 W / m · K), more preferably 150 W / m · K or more (for example, 150 to 1000 W / m · K). If the graphite having too low thermal conductivity is used, the thermal conductivity of the composition becomes low.

The graphite is contained in an amount of 10 to 50% by weight, preferably 30 to 50% by weight in 100% by weight of the resin composition of the present invention. If the content of graphite in the composition is less than 10% by weight, the thermal conductivity is lowered. If the content is more than 50% by weight, the workability is lowered and it is difficult to secure the mass productivity.

With carbon nanotubes Reformed  Glass fiber

The resin composition of the present invention includes glass fibers (Carbon Enhanced Reinforcements, CER) modified with carbon nanotubes as a heat-radiating filler.

In the thermally conductive resin composition, it has been common to apply glass fiber as a reinforcing material and carbon nanotubes together as a heat radiating filler. However, in this case, it is impossible to disperse the entangled carbon nanotubes in the extrusion or injection molding process, and therefore, an additional step of dispersing the carbon nanotubes before processing is inevitable. As an additional physical method for dispersing the carbon nanotubes, there is a method of dispersing by using a surfactant and an ultrasonic wave, and an acid treatment method of introducing a functional group onto the surface of the carbon nanotube with a strong acid such as sulfuric acid or nitric acid by a chemical method have. However, not all of these methods have a limitation on the dispersion capacity, but also affect the carbon nanotube structure and further increase the cost due to the additional process.

However, in the present invention, by using carbon nanotube-modified glass fibers (CER) obtained by directly growing carbon nanotubes on the surface of glass fibers, there is no need for a separate carbon nanotube dispersion step, .

In the glass fiber (CER) modified with the carbon nanotubes, the diameter of the glass fiber is preferably 8 to 15 mu m, more preferably 10 to 13 mu m. If the diameter of the glass fiber is less than 8 占 퐉, the flowability may be lowered during extrusion processing. Conversely, if it exceeds 15 占 퐉, it may be difficult to ensure mechanical properties due to deterioration of adhesion to resin. In the CER, the glass fiber is preferably chopped, and its length is preferably 3 to 10 mm, more preferably 4 to 6 mm. If the length of the glass fiber is less than 3 mm, it may be difficult to secure the mechanical properties. If the length exceeds 10 mm, it may be difficult to secure the workability due to a decrease in fluidity during extrusion processing.

In the CER, the carbon nanotubes grown on the glass fiber surface can be both multi-wall type and single-wall type, and the multi-wall type is more preferable in the manufacturing process, It is not.

In the CER, the length of the carbon nanotubes grown on the glass fiber surface is preferably 100 to 300 mu m, more preferably 150 to 250 mu m. If the length of the carbon nanotubes is less than 100 mu m, the thermal conductivity and the electric conduction characteristics may be deteriorated. If the length is more than 300 mu m, the anisotropy of the thermal conductivity may be increased.

The content of the carbon nanotubes in the CER is preferably 10 to 25% by weight, more preferably 10 to 22% by weight, based on 100% by weight of the total CER. If the content of the carbon nanotubes in the CER is less than 10% by weight, it is difficult to expect the thermal conductivity and the electric conduction property, and if it exceeds 25% by weight, it may become difficult to secure mechanical properties.

The CER is contained in an amount of 5 to 40% by weight, preferably 10 to 40% by weight within 100% by weight of the resin composition of the present invention. If the CER content in the composition is less than 5% by weight, a synergistic effect of thermal conductivity and mechanical properties can not be expected. If the CER content exceeds 40% by weight, the extrusion processability is deteriorated.

Other additives

The composition of the present invention may contain, in addition to the above-described components, various additives commonly used in thermoplastic resin compositions such as heat stabilizers, antioxidants, lubricants, coupling agents, impact modifiers, May be further included. The amount of the additive to be used is not particularly limited and may be further added in an amount of up to about 5 parts by weight, preferably about 0.2 to 5 parts by weight, based on 100 parts by weight of the total resin composition, depending on the intended use and application.

The resin composition of the present invention can be obtained by blending the components through a melt kneading process known in the art. For this purpose, a resin composition such as a ribbon blender, Henschel mixer, Banbury mixer, drum tumbler, single screw extruder, , A multi-screw extruder, or the like.

The resin composition of the present invention thus obtained has excellent physical properties including thermal conductivity and mechanical properties, exhibits reduced anisotropy of thermal conductivity, possesses mass productivity using a twin-screw extruder, and moldability applicable to an injection process . Thus, extrusion / injection molding can be used to obtain molded articles useful for automotive (e.g., interior / exterior), electrical / electronic (e.g., housing) or lighting (e.g., LED lighting) applications.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the scope of the present invention is not limited thereto.

[ Example ]

Component used

1) linear polyphenylene sulfide resin

: HATON PPS hb0 (SCDY), flow index (MFR, 1.2 kg, 300 캜): 60 g / 10 min, bulk density of about 0.5 g / cm ³ , flow index 300 캜, minute

2) Glass fiber

: 910-10P (OCV yarn), diameter: 10 mu m, length: 4 mm

3) Graphite

: SHOCARAISER S grade (Showa Denko Co.), average particle diameter: 200 탆, bulk density: 0.8 g / cm 3

4) CER (glass fiber modified with carbon nanotube (CNT))

: CER chop (OCV yarn), glass fiber length: 4.5 mm, glass fiber diameter: 10 탆, CNT length: 200 탆, CNT content: 20 wt%

Example  1-5

Polyphenylene sulfide resin (HATON PPS hb0, SCDY Co.) having a flow index of 60 g / 10 min was charged into a primary inlet of a twin-screw extruder with L / D = 40 and Φ = 25 (mm) (SHERKARAISER S grade, Showa Denko) was charged into a second charging port. CER (CER chop, OCV) was charged into the third charging port of the twin-screw extruder and extruded at an extrusion temperature of 320 to 350 ° C., And extruded at 150 to 250 rpm to prepare a pelletized resin composition.

Comparative Example  1-4

Polyphenylene sulfide resin (HATON PPS hb0, SCDY Co.) having a flow index of 60 g / 10 min was charged into a primary inlet of a twin-screw extruder with L / D = 40 and Φ = 25 (mm) And a graphite (SHOCARAISER S grade, Showa Denko) was charged into a second charging port. Glass fiber (910-10P, OCV yarn) was charged into the third charging port of the twin-screw extruder and extruded at a temperature of 320 to 350 ° C, And extruded at a rotational speed of 150 to 250 rpm to prepare a pelletized resin composition.

Physical property test

The pelletized resin compositions prepared in each of the Examples and Comparative Examples were fixed at a cylinder temperature of about 300 to 350 DEG C and a mold temperature of 130 DEG C and then injection molded to prepare specimens. . The test results are shown in Table 2 below (parentheses are standards required for the properties).

(1) Through-Plane

: ASTM E1451, thickness: 2.0 mm, unit: W / m · K

(2) Thermal conductivity (In-Plane)

: ASTM E1451, thickness: 2.0 mm, unit: W / m · K

(3) Thermal conductivity

: = Thermal conductivity (In-Plane) - Thermal conductivity (Through-Plane) (must be 15 or less)

(4) Electrical conductivity (electric volume resistance)

: ASTM D257, thickness: 2.0 mm, unit: Ω · cm (should be 10 ⁸ or less)

(5) Flexural modulus

: ASTM D790, crosshead speed: 10 mm / min, unit: kgf / cm ² (must be more than 130,000)

 (6) Extrusion processability

: Measured using torque meter of twin-screw extruder, unit: N · m (should be less than 65)

As can be seen from the results of the physical properties test shown in Table 2, the resin compositions prepared in Examples 1 to 5 of the present invention satisfied the requirements in all of the physical property evaluation items. Particularly, excellent thermal conductivity and reduced thermal conductivity anisotropy Respectively. On the other hand, none of the resin compositions of the comparative examples satisfies the requirements in all of the physical property evaluation items, and in particular, all comparative compositions fail to satisfy the requirements for thermal conductivity anisotropy (thermal conductivity).

Claims (9)

10 to 85% by weight of polyphenylene sulfide resin, 10 to 50% by weight of graphite, and 5 to 40% by weight of glass fibers modified with carbon nanotubes. The resin composition according to claim 1, wherein the polyphenylene sulfide resin has a bulk density of 0.2 to 1.5 g / cm ³ . The resin composition according to claim 1, wherein the graphite has a bulk density of 0.3 to 2 g / cm ³ and a particle size of 10 to 500 μm. The resin composition according to claim 1, wherein the graphite has a thermal conductivity of 100 W / m · K or more. The resin composition according to claim 1, wherein the glass fiber used for the glass fiber modified with carbon nanotubes has a diameter of 8 to 15 mu m and a length of 3 to 10 mm. The resin composition according to claim 1, wherein the length of the carbon nanotubes in the glass fiber modified with the carbon nanotubes is 100 to 300 mu m. The resin composition according to claim 1, wherein the content of the carbon nanotubes in the glass fibers modified with the carbon nanotubes is 10 to 25% by weight based on the total weight of the glass fibers modified with the carbon nanotubes. A molded article produced by processing the thermally conductive, electrically conductive, and thermoplastic resin composition of any one of claims 1 to 7. The molded article according to claim 8, characterized in that it is an automobile, an electric appliance, an electronic appliance or an illumination appliance.