JPH07103291B2 - Conductive resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a conductive resin composition, and more specifically, it has excellent impact resistance, high conductivity, and unnecessary electromagnetic wave shielding performance. The present invention relates to a conductive resin composition suitable for electric and electronic parts, electronic device housings and automobile parts that require

(Problems to be Solved by Conventional Techniques and Inventions) In recent years, with the rapid spread of OA equipment, malfunctions due to unnecessary electromagnetic waves radiated from these equipment, loss of magnetic recording information, etc. have been greatly highlighted. .

As a countermeasure against unnecessary electromagnetic waves, conventionally, a conductive resin, which is a metal plate or resin itself having conductivity, has been used as a material for a device housing. In particular, conductive resins are excellent in molding processability, so they are powdery, flaky,
Alternatively, many products containing a fibrous conductive filler have been developed and put on the market.

In particular, the one in which the metal fiber is mixed as the fibrous conductive filler can obtain an excellent electromagnetic wave shielding effect with a relatively small amount of the compound, but the mechanical properties, especially the impact resistance are inevitably deteriorated.

On the other hand, polybutylene terephthalate resin (PBT resin)
Has excellent chemical resistance, low water absorption, and moldability.
In recent years, it has attracted attention as a molding material for injection molding and the like, and its great utility value has been recognized as electric and electronic parts, mechanical parts, and automobile parts. However, the PBT resin as a molding material has a drawback that the impact strength in a notched Izod test piece is small because of its crystallization behavior, and when a metal fiber is added to impart electromagnetic wave shielding performance, the impact resistance is low. The sex is practically unbearable.

As a method for improving the impact resistance of the PBT resin, alloying with a rubber component has been studied. For example, in JP-A-49-97081, the impact strength of the PBT resin is obtained by mixing the PBT resin and the ABS resin. However, when metal fibers were added to this composition, the impact strength was reduced and the impact resistance was insufficient.

The present inventors have completed the present invention as a result of intensive studies to solve the above-mentioned problems. An object of the present invention is to provide a conductive resin composition having excellent impact resistance and conductivity.

(Means for Solving the Problems) That is, the conductive resin composition of the present invention contains 10-150 parts by weight of an acrylate copolymer and 8 parts by weight of metal fibers with respect to 100 parts by weight of a polybutylene terephthalate resin. 800 parts by weight of the acrylic acid ester copolymer, wherein the acrylic acid ester copolymer has 1 to 5 carbon atoms and an acrylic acid ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon group.
It is a copolymer with a methacrylic acid ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon of -5.

The present invention will be described in detail below.

The polybutylene terephthalate resin used in the present invention is
It is a polymer obtained by reacting an aromatic dicarboxylic acid or its diester with a glycol containing tetramethylene glycol as a main glycol component by a known method. Specifically, the main component is terephthalic acid or dimethyl terephthalate, and isophthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,
An aromatic dicarboxylic acid prepared by appropriately combining 4'-diphenoxyethanedicarboxylic acid, p-oxybenzoic acid, sebacic acid, adipic acid and the like, and tetramethylene glycol as a main component, ethylene glycol or ethylene oxide, trimethylene glycol , Hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol, and the like, which are polycondensed with a glycol which is appropriately used in combination.

The acrylic acid ester copolymer used in the present invention comprises an acrylic acid ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 5 carbon atoms and 1 carbon atom.
It is a copolymer with a methacrylic acid ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon group of -5.

Here, as the acrylate ester having a saturated or unsaturated straight chain or branched chain aliphatic hydrocarbon group having 1 to 5 carbon atoms, methyl acrylate, ethyl acrylate, isobutyl acrylate, diacrylic acid-1,4 are preferable. -Butanediol, 1,3-butylene diacrylate.

Further, as the methacrylic acid ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 5 carbon atoms, methyl methacrylate, ethyl methacrylate,
There are isobutyl methacrylate, 1,3-butylene dimethacrylate, and n-butyl methacrylate. As such an acrylic acid ester copolymer, those commercially available from Roll & Haas Company under the trade name "Paraloid KM-330" are preferable.

In the present invention, the amount of the acrylic ester copolymer blended is important to be 10-150 parts by weight, particularly 20-1
20 parts by weight is preferred.

If the amount of the acrylic acid ester copolymer is less than 10 parts by weight, the impact resistance is insufficient. On the other hand, if the amount of the acrylic acid ester copolymer to be blended exceeds 150 parts by weight, it causes poor heat resistance.

The metal fibers used in the present invention include, but are not limited to, iron, aluminum, nickel, copper and alloys of these metals. Particularly preferred are brass fiber, low carbon steel alloy fiber, and stainless steel fiber.

The shape of the metal fiber is usually 5-150μ in diameter and 0.5-15 in fiber length.
The mm one is used.

In the present invention, it is essential that the amount of the metal fiber compounded is 8-800 parts by weight, preferably 15-500 parts by weight, per 100 parts by weight of the polybutylene terephthalate resin. When the amount of the metal fibers is less than 8 parts by weight, the effect of imparting conductivity is insufficient. On the other hand, when it exceeds 800 parts by weight, the fluidity is lowered and the molding process by the injection molding method becomes extremely difficult.

A colorant, a heat stabilizer, a lubricant, a crystal nucleating agent and the like can be further added to the composition of the present invention, if necessary.

It is important that the composition of the present invention is sufficiently kneaded and dispersed until it becomes a final molded product. As a method for this purpose, for example, a pellet-shaped resin may be produced by using a different-direction rotating twin-screw kneading extruder and subjected to a molding step.

(Example) Hereinafter, the present invention will be specifically described with reference to examples. Incidentally, the evaluation of physical properties was carried out according to the following methods.

1. Izod impact strength (1/4 inch, notched): ASTM
D-256 2. Heat distortion temperature (18.6 kg / cm ² ): ASTM D-648 3. Volume resistivity: ASTM D-257 Example 1-6, Comparative example 1-4 Polybutylene terephthalate resin (Kanebo Corp.) Kanebo PBT719) 100 parts by weight, brass fiber (KC-Metal Fiber C-2600 manufactured by Kobe Cast Iron Co., Ltd.) and acrylic ester copolymer (Paraloid KM manufactured by Rohm & Haas)
-330) was compounded in the composition shown in Table 1 and pelletized using a 25 mm diameter single-screw kneading extruder.

The obtained pellets were molded into a test piece using an injection molding machine, and the test piece was evaluated. These results are shown in Table-1.
Shown in.

Example 7, Comparative Example 5-7 100 parts by weight of polybutylene terephthalate resin (Kanebo PBT719, manufactured by Kanebo Co., Ltd.) was added to low carbon steel alloy fiber (S15C, Kobe Cast Iron Co., Ltd., diameter 50 μmφ, length 2 mm). ) 100
Parts by weight and 50 parts by weight of the impact resistance modifier shown in Table 2 were blended and pelletized using a 30 mm diameter biaxial counter-rotating kneading extruder. Then, the test piece was molded, and the physical properties of the test piece were evaluated. The results are shown in Table-2.

As can be seen from Table-1 and Table-2, the conductive resin composition according to the present invention is a conductive resin composition excellent in impact resistance and conductivity.

(Effects of the Invention) The conductive resin composition of the present invention is excellent in impact resistance and conductivity, and is suitable for electric / electronic parts, electronic equipment casings, or automobile parts.

Claims (1)

[Claims] 1. A polybutylene terephthalate resin of 100 parts by weight is blended with 10 to 150 parts by weight of an acrylic acid ester copolymer and 8 to 800 parts by weight of a metal fiber, and the acrylic acid ester copolymer is Acrylic ester having a saturated or unsaturated linear or branched aliphatic hydrocarbon group having 1 to 5 carbon atoms and methacryl having a saturated or unsaturated linear or branched aliphatic hydrocarbon having 1 to 5 carbon atoms A conductive resin composition, which is a copolymer with an acid ester.