JP2006057064A - Thermoplastic resin molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoplastic resin molded article showing high thermal conductivity even on producing the resin molded article by injection molding, and having an excellent molding processability. <P>SOLUTION: This thermoplastic resin molded article is obtained by blending a tetrapod-formed zinc oxide whisker consisting of a core part and needle-like crystal parts extending from the core part in 4 different axial directions and a fine filler material having ≤100 nm mean particle diameter, with a thermoplastic resin. The thermoplastic resin molded article is one that the ratio of total blending amount of the tetrapod-formed zinc oxide whisker and fine filler material is ≥15 vol.%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoplastic resin molded article excellent in thermal conductivity and molding processability obtained by blending a tetrapot-like zinc oxide whisker and a fine filler.

  In recent years, with the miniaturization and high performance of electric / electronic components, heat generation in the components has become remarkable, and there has been a problem that the performance of the equipment is deteriorated due to heat accumulation. Therefore, a material excellent in thermal conductivity is required from the viewpoint of safety and reliability. Conventionally, metal materials have been used for materials that require high thermal conductivity. However, materials are required to be lightweight and easy to process to reduce the size and performance of parts. Substitution is progressing. However, the resin has low thermal conductivity from the beginning, and there is a limit to increasing the thermal conductivity of the resin itself. In view of this, a method has been performed in which a resin having a high thermal conductivity (for example, alumina, magnesium oxide, boron nitride, carbon fiber, or the like) is highly filled in a resin to increase the thermal conductivity of the resin composition (for example, Patent Documents). 1).

JP-A-8-73651

When the particulate filler material is blended with the resin, a large amount of filler material is required to increase the thermal conductivity of the resin molded body. When the filling amount is large, the fluidity of the molded body is lowered and the molding process becomes difficult. When the fibrous filler is blended, the contact probability between the fibers is higher than that of the particulate filler, and a heat conduction path is easily formed. Therefore, a high thermal conductivity can be expected with a smaller filling amount than the particulate filler. However, when a resin molded body is produced by injection molding, the fibers tend to be oriented parallel to the injection direction, so the contact probability between the fibers is lower than that when the fibers are randomly dispersed.
In view of such problems, the present invention is to provide a thermoplastic resin molded body that exhibits high thermal conductivity and has excellent molding processability even when a resin molded body is produced by injection molding. .

  That is, the present invention includes a thermoplastic resin containing a tetrapot-like zinc oxide whisker having a core and needle-like crystal parts extending in different four-axis directions from the core and a fine filler having an average particle size of 100 nm or less. This is related to a thermoplastic resin molded body obtained by molding.

The thermoplastic resin used in the thermoplastic resin molded article of the present invention refers to a synthetic resin that can be molded, but a particularly effective thermoplastic resin for the purpose of the present invention is a liquid crystalline polyester. The liquid crystal polyester is a polyester called a thermotropic liquid crystal polymer, (1) obtained by reacting a combination of an aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid and an aromatic diol, and (2) a different kind of aromatic hydroxy. Obtained by reacting carboxylic acid, (3) obtained by reacting a combination of aromatic dicarboxylic acid and aromatic diol, and (4) reacting aromatic hydroxycarboxylic acid with polyester such as polyethylene terephthalate. What is obtained etc. are mentioned, What forms an anisotropic melt at the temperature of 400 degrees C or less is preferable.
In addition, these ester-forming derivatives may be used in place of these aromatic dicarboxylic acids, aromatic diols and aromatic hydroxycarboxylic acids.
Examples of the repeating structural unit of the liquid crystalline polyester include the following, but are not limited thereto.

（上記の繰り返し構造単位は、ハロゲン原子、アルキル基またはアリール基で置換されていてもよい。） Repeating structural units derived from aromatic hydroxycarboxylic acids:

(The above repeating structural unit may be substituted with a halogen atom, an alkyl group or an aryl group.)

（上記の繰り返し構造単位は、ハロゲン原子、アルキル基またはアリール基で置換されていてもよい。） Repeating structural units derived from aromatic dicarboxylic acids:

(The above repeating structural unit may be substituted with a halogen atom, an alkyl group or an aryl group.)

Repeating structural units derived from aromatic diols:

（上記の繰り返し構造単位は、ハロゲン原子、アルキル基またはアリール基で置換されていてもよい。）

(The above repeating structural unit may be substituted with a halogen atom, an alkyl group or an aryl group.)

A particularly preferred liquid crystalline polyester from the balance of heat resistance, mechanical properties and processability is _one containing at least 30 mol% of the repeating structural unit represented by (A ₁ ).

Specifically, the combination of repeating structural units is preferably those of the following formulas (a) to (f).
(A): (A ₁ ), (B ₁ ) or a mixture of (B ₁ ) and (B ₂ ), (C ₁ ).
(B): (A ₁ ), (A ₂ ).
(C): A combination of structural units of (a), wherein A ₁ is partially replaced by A ₂ .
(D): A combination of the structural units of (a), wherein a part of B ₁ is replaced with B ₃ .
(E): A combination of structural units in (a), wherein a part of C ₁ is replaced with C ₃ .
(F): A combination of the structural units of (b) plus the structural units of B ₁ and C ₂ .
The basic liquid crystal polyesters (a) and (b) are described in, for example, Japanese Patent Publication No. 47-47870 and Japanese Patent Publication No. 63-3888.

  In the present invention, as the filler, a tetrapot-like zinc oxide whisker and a fine filler having an average particle size of 100 nm or less are essential components.

  The tetrapot-like zinc oxide whisker used in the present invention comprises a core part and a needle-like crystal part extending from the core part in different four-axis directions, and the diameter of the base part of the needle-like crystal part is preferably 0.00. The length from the base to the tip of the acicular crystal part is preferably 3 to 200 μm. Such tetrapot-like zinc oxide whiskers are obtained by the method described in JP-A-1-252599, and various grades are commercially available from Matsushita Sangyo Information Equipment Co., Ltd.

  The fine filler material used in the present invention has an average particle size of 100 nm or less, preferably 50 nm or less. Moreover, it is preferable that the thermal conductivity of the fine filling material is 10 W / mK or more at 20 ° C. Particularly effective microfill materials for the purposes of the present invention are zinc oxide and aluminum oxide.

  In the present invention, the volume fraction of the total blended amount of the tetrapot-like zinc oxide whisker and the fine filler is preferably 15% by volume or more. When the total amount is small, the number of contact points between the fillers is small, and it is not effective for improving the thermal conductivity. If the total blending amount is too large, the fluidity at the time of molding processing is lowered and the molded body becomes brittle. Therefore, the total blending amount is preferably 70% by volume or less. Here, the total volume% of the tetrapot-like zinc oxide whisker and the fine filling material is obtained by decomposing the resin at a temperature higher than the decomposition temperature of the resin and lower than the decomposition temperature of the filler, for example. Except for this, it is determined by the ratio of the sum of the volume obtained from the weight of each remaining filler and the true specific gravity at 0 ° C. and the volume of the molded body.

  The blending ratio of the tetrapot-shaped zinc oxide whisker and the fine filler is not particularly limited and may be appropriately selected from a wide range, but is preferably 90:10 to 70:30. Further, like the conventional resin composition, in order to improve the adhesion between the resin and the filler, the surface of the filler can be treated with a silane coupling agent or the like prior to blending.

  In the present invention, a filler such as glass fiber, a mold release improver such as a fluororesin and a metal soap, a colorant such as a dye and a pigment, an antioxidant, a heat, and the like within a range not impairing the object of the present invention. One or more ordinary additives such as stabilizers, ultraviolet absorbers, antistatic agents, and surfactants may be added and used. Moreover, you may add and use 1 or more types which have external lubricant effects, such as a higher fatty acid, a higher fatty acid ester, a higher fatty acid metal salt, and a fluorocarbon type surfactant.

  Further, the blending means in the present invention is not particularly limited. It is preferable that the thermoplastic resin and the filler are mixed using a Henschel mixer, a tumbler or the like and then melt-kneaded using an extruder. The molded article of the present invention includes pellets, but the present invention is particularly suitable for a thermoplastic resin molded article obtained by injection molding. The thermoplastic resin molded article of the present invention is useful as a material for electronic parts such as coil bobbins, relay parts, and connectors.

EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited by an Example.
Example 1 and Comparative Examples 1 and 2
The repeating structural unit is composed of A ₁ , B ₁ , B ₂ , and C ₁ described above, and the molar ratio of A ₁ : B ₁ : B ₂ : C ₁ is 60: 15: 5: 20. Liquid crystal polyester having a flow temperature of 323 ° C., “Panatetra WZ-0511” (trade name, manufactured by Matsushita Sangyo Information Equipment Co., Ltd.) as a tetrapotted zinc oxide whisker, and zinc oxide fine particles having an average particle diameter of 30 nm or 11 μm After mixing with each composition shown in Table 1, using a twin screw extruder (PCM-30 type, manufactured by Ikegai Iron Works Co., Ltd.), melt-kneading, then extruding the strand, cooling the strand with water and cutting it into pellets Got. After drying this pellet at 120 ° C. for 3 hours or more, a molded body having a shape of 100 × 100 × 3 t (mm) was injection-molded, and the thermal conductivity in the thickness direction perpendicular to the injection direction was determined by a hot wire method. It was measured. The results are shown in Table 1.
Comparative Examples 3 and 4
Liquid crystal polyester and zinc oxide fine particles having an average particle diameter of 30 nm or 11 μm were mixed in the composition shown in Table 1 and melt kneaded with a twin screw extruder. Both of them were brittle and continuous pellets could be obtained. could not.

Claims (5)

  Obtained by blending a thermoplastic resin with a tetrapot-like zinc oxide whisker composed of a core part and needle-like crystal parts extending in different four-axis directions from the core part and a fine filler having an average particle size of 100 nm or less. Thermoplastic resin molded product. The thermoplastic resin molded article according to claim 1, wherein the thermoplastic resin is a liquid crystalline polyester resin having a flow temperature defined below of 260 to 400 ° C.
Flow temperature: Using a capillary rheometer with a nozzle with an inner diameter of 1 mm and a length of 10 mm, when a heated melt is extruded from the nozzle at a heating rate of 4 ° C / min under a load of 100 kg / cm ² , the melt viscosity is 48000 Temperature indicating poise   The thermoplastic resin molded article according to claim 1 or 2, wherein the total amount of tetrapot-like zinc oxide whisker and fine filler is 15% by volume or more.   The thermoplastic resin molded body according to any one of claims 1 to 3, wherein the thermal conductivity of the microfilling material is 10 W / mK or more at 20 ° C. The thermoplastic resin molded body according to any one of claims 1 to 4, wherein the minute filler is zinc oxide.