JPS6386755A - Electrically conductive thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain the titled resin composition, containing SUS304 stainless steel fibers having a specific average fiber diameter, average fiber length and aspect ratio and capable of giving molded articles having improved electric conductivity as well as electromagnetic wave shielding ability even after passing through heat cycles. CONSTITUTION:A composition obtained by melt blending (A) 96-85wt% thermoplastic resin with (B) 4-15wt% SUS304 stainless steel fibers, having 2-20mum, preferably 4-12mum average fiber diameter, 0.5-10mm, preferably 2-10mm fiber length and 200-1,000, preferably 200-700 aspect ratio, preferably collected with a binder and, as necessary, melt blending an additive, e.g. flame retardant, colorant, plasticizer, etc., using a Henschel mixer, etc.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to a conductive thermoplastic resin composition.

For more details, molded products with stable conductivity and excellent electromagnetic shielding ability even after undergoing heat cycles! This invention relates to a conductive thermoplastic resin IiL container suitable for personal use.

"Conventional Technology" In recent years, with the rapid spread of electronic devices, a new social problem has arisen: electromagnetic interference. i.e. office equipment,
Electronic devices such as electronic meters and television receivers are not only subject to interference from unnecessary electromagnetic waves generated by other electronic devices, but also generate unnecessary electromagnetic waves from their own circuits and elements.
Other electrons 8! Causes damage to the vessel. The phenomenon in which electronic devices interfere with each other due to these unnecessary electromagnetic waves is called electromagnetic interference.

Measures against electromagnetic interference include so-called secondary measures, which suppress the generation of unnecessary electromagnetic waves themselves, and so-called secondary measures, which prevent the leakage of generated unnecessary electromagnetic waves or the intrusion of unnecessary electromagnetic waves coming from outside. There are certain means.

However, electronic devices are changing from IC to LIS and even VL
As S'I continues to become faster and more highly integrated, the generation of unnecessary electromagnetic waves is even on the rise, and it must be said that the following methods naturally have their limits.

Therefore, expectations for unnecessary electromagnetic wave shielding technology as a secondary means are very high, and it has now been positioned as a pillar of measures to prevent electromagnetic interference.

In order to avoid electromagnetic interference by shielding unnecessary electromagnetic waves coming from the outside, basically it is sufficient to cover the electronic device with a housing having appropriate conductivity, for example, a metal housing.

However, the housings of electronic devices are now mostly made of thermoplastic resin, replacing the previous ones made of sheet metal or aluminum cast. This is due to the excellent material properties of thermoplastic resins, such as ease of molding, freedom of design and coloring, and lightweight molded products.

However, since a normal thermoplastic resin is an electrical insulator, it has no ability to shield electromagnetic waves at all.

Against this background, studies have been conducted on thermoplastic resin 91 casings that have electromagnetic wave shielding ability, and technologies for making thermoplastic resin molded products with conductive surface treatment and thermoplastic resin compositions blended with conductive materials have been developed. Techniques have been proposed to create molded products made of objects.

However, these proposed techniques have the following drawbacks.

First of all, there are known techniques for making thermoplastic resin molded products whose surfaces have been treated to conductivity, such as applying conductive paint to the surface of the molded product or thermally spraying zinc or aluminum to form a conductive coating layer. There is. However, in order to obtain these thermoplastic resin molded products whose surfaces have been treated to make them conductive, a new process is added to form a coating layer of conductive material on the surface of the molded product, and this is also required for the casing. When used as an electronic device, there is always a risk that the coating layer of the conductive material may crack, peel, or come off, leaving concerns about the reliability of the electronic device.

Next, the technology for imparting conductivity to thermoplastic resin is as follows:
Composite materials are known in which conductive fillers such as metal powder, carbon fibers, and metal fibers are blended and dispersed in a thermoplastic resin material as a base material.

However, this type of conductive thermoplastic resin composition obtained using American technology has insufficient electromagnetic wave shielding ability unless it contains a large amount of conductive filler; 1 (physical properties of the fat composition are impaired,
There was a problem that the moldability was deteriorated and the mechanical properties of the obtained molded article were also inferior.

In addition, although molded products made of conventional conductive thermoplastic tree layers exhibit almost satisfactory conductivity and electromagnetic wave shielding ability under normal conditions, repeated temperature changes between, for example, below 0°C and above 70°C When subjected to continuous heat cycle treatments such as the above, the conductivity was gradually lost and the electromagnetic wave shielding ability was insufficient, so that it could not be said to be satisfactory from these five points.

"Second generation of problems to be solved by the invention" Therefore, in view of the problems of the above-mentioned American technology, the present inventors have found that a molded product with good moldability and excellent mechanical properties can be obtained, and this molded product The present invention was completed as a result of intensive research to provide a conductive thermoplastic resin MLrit product that exhibits stable conductivity and excellent electromagnetic shielding ability even when subjected to severe heat cycles.

"Means for Solving the Problems" However, the gist of the present invention is to combine thermoplastic resin (a) and 5O8304 stainless fiber (b) into (a
) component above (/contains the ratio of component (b) to the total amount of component (b) in the range of 4 to 15% by weight, and the 5Us3
04th? Nle xjiJa(b)l! , average am diameter 2~2
0 μm, average fiber length of 0.5 to 10 mm, and aspect ratio of 200 to 1000.

The present invention will be explained in detail below.

The conductive thermoplastic resin composition according to the present invention has a thermoplastic resin (Otori) as its base. Thermoplastic resin (,
) may be any thermoplastic resin that is commonly used as a molding material, and there are no particular restrictions.Specifically, for example, styrenic resins such as polystyrene, impact-resistant polystyrene, AS resin, and ABS resin; polyethylene, polypropylene Olefins such as 11 fats; Polyester PS such as polyethylene terephthalate and polybutylene terephthalate
Resin; polyamide resin, polycarbonate resin,
Examples include vinyl chloride resins and blends of these resins.

SUS 304 stainless steel # & Jli (
b) is SUS specified in JIS G-4303~8
Made of 304 stainless steel, average fiber diameter 2-20 μm & P preferably 1 ± 4-12 μm, average fiber, III 0.5
-10 mm, preferably 2-10 mm, and the aspect ratio (value obtained by dividing the am length by the fiber diameter) is 200-1000.
Preferably it is 200-700.

According to experiments conducted by the present inventors, in order to achieve the object of the present invention, SUS304 stainless steel fibers having the above-mentioned characteristics are suitable as the conductive filler to be blended into the thermoplastic resin that serves as the base. understood.

Instead of the above SUS304 stainless steel fiber, JIs
When stainless steel other than SUS304 stainless steel specified in G-4303 to G-8, for example, stainless fiber made of SUS316 stainless steel is blended, the object of the present invention can be achieved even if the shape is within the above range. I can't.

The average fiber diameter of SUS304 stainless steel fiber (b) is 2μ
- If the strength is below, the strength of the fiber itself will be insufficient, and when blending the stainless steel fiber into the thermoplastic resin (a) that becomes the base, the thin stainless steel fibers will easily become entangled with each other and form a pill, so that the strength of the fiber itself will be insufficient. It is natural to disperse,
Moreover, the stainless steel fibers break during dispersion, making it impossible to impart sufficient electrical conductivity to molded articles obtained from the composition.

Furthermore, if the average fiber diameter of the SUS304 stainless fiber (b) is 20μ or more, the efficiency of imparting conductivity per unit weight of the stainless fiber is low, and the conductive thermoplastic resin composition containing the stainless fiber is low. The molded products obtained from this method have poor surface smoothness and are not practical.

If the average fiber length of the SUS304 stainless steel fiber Jlli (b) is 0.5IIIm or less, the aspect ratio will be small and it will not be possible to impart optical conductivity to a molded article obtained from the composition, making it impractical.

In addition, if the average fiber length of the SUS304 stainless steel fiber (b) is 10 or more, when the stainless steel M&fiber is blended into the base thermoplastic resin Ca, the long stainless steel fibers are likely to become entangled with each other and form a pill. Therefore, it is difficult to disperse uniformly, and this stainless steel a#l
A molded article obtained from a conductive thermoplastic resin IL product containing the above has poor surface smoothness and is not practical.

In addition, if the 7 aspect ratio of SUS304 stainless steel Jlt(b) is less than 200, the efficiency of imparting conductivity and electromagnetic shielding ability to the molded product obtained from the composition is low and impractical, and the aspect ratio is greater than 1000. When blending these stainless steel fibers into the base thermoplastic resin (a), the #I stainless steel fibers tend to get entangled with each other and form a pill shape, making it difficult to uniformly disperse the stainless steel fibers into the base. The fibers break due to the external force applied during the four-crop process, making it impractical to impart sufficient electrical conductivity and electromagnetic wave shielding ability to a molded article obtained from the composition.

In the conductive thermoplastic resin composition of the present invention,
It is necessary that the SUS 304 stainless fiber (b) weighs 4 to 15 percent by weight based on the total amount of the thermoplastic JJI (a) and the SUS 304 stainless steel fiber (b).

The content of the above SUS304 stainless steel fiber II (b) is 4
If it is less than 15% by weight, the conductivity and electromagnetic shielding ability of the molded product obtained from the composition will be insufficient and impractical, and if it exceeds 15% by weight, the molded product will have poor conductivity and electromagnetic shielding ability. This is not preferable because it does not significantly improve the molding processability of the M product, and also impairs the thermoplasticity of the base material (the physical properties inherent in the fat).

Next, in order to produce the conductive thermoplastic resin (fat assembly product) according to the present invention, the thermoplastic resin (a) and the SUS304 stainless steel fiber (b) having the above characteristics are mixed in a Henschel Miser or Banbury mixer. −, Niegoo, single pongee extrusion time,
A method of cross-dispersion using a melt mixer such as a twin-screw extruder can be adopted.

In order to delay this crosstalk dispersion fabrication more smoothly, it is preferable to use S tJ S 304 stainless steel fibers with convergent deafness.

Here, what is SUS304 stainless steel fiber of convergence deafness?
Monofilament-like 5O5304 having the above-described uniform fiber diameter
A plurality of long stainless steel fibers, for example, several to several hundred long fibers, are bundled together using a sizing agent, and the bundle of long fibers has the above-mentioned characteristics such as uniform weave length and aspect ratio. It refers to what is called a titasobud strand that is cut like this.

As a sizing agent that can be used when sizing single-filament SUS304 stainless steel long & tJIII, it is best to use a resin that is compatible with the base thermoplastic O (fat) and does not inhibit its properties. There are no particular restrictions.

Such a sizing agent can be used in the form of a solution or emalnotane.

When such SUS304 stainless steel fibers are bundled with a binding agent, the stainless steel fibers will not be scattered during crosstalk dispersion fabrication, and therefore the working environment can be prevented from deteriorating. In addition, stainless steel a in the kneading process
This is preferred because it can further reduce the entanglement and breakage of fibers, and it can impart excellent conductivity and electromagnetic wave shielding ability to molded products obtained from the composition.

The conductive thermoplastic resin composition according to the present invention includes the above (a)
) In addition to the rjt and ([)) components, as long as they do not inhibit the properties of the M acid, TL retardants, colorants, plasticizers, ultraviolet absorbers, lubricants, heat stabilizers, and antistatic agents may be added as necessary. , and various other additives may also be included.

The conductive thermoplastic resin M acid according to the present invention can be used for various electronic 8
! It can be used as a manufacturing material for equipment casings, containers for integrated circuits, etc., and can also be used as flooring, ceiling, and wall materials in computer rooms, etc. by coloring it in the desired color. .

"Effects of the Invention" The present invention has the contents as described in detail above, and has particularly remarkable effects as described below, so that its industrial utility value is extremely large.

(a) The conductive thermoplastic resin composition according to the present invention has a low content of conductive filler, and thus exhibits good moldability.

2) Since the conductive thermoplastic resin 1jLr& product according to the present invention can be manufactured by the commonly used crosstalk dispersion method, no special equipment or special process is required for manufacturing, and the manufacturing method is rrJ. It's simple.

(3) Since the conductive thermoplastic t34f'XI composition according to the present invention contains 5tJS 304 stainless steel fibers having the characteristics specified in the present invention as a conductive filler,
Despite its low content of 1, molded articles obtained from this composition exhibit excellent electrical conductivity and electromagnetic wave shielding ability.

(4) The conductive thermoplastic according to the present invention (3) The molded product obtained from the resin composite product exhibits good conductivity and electromagnetic wave shielding ability under normal conditions, and is resistant to changes in severe temperature conditions (heat cycle). It exhibits stable conductivity and electromagnetic wave shielding ability even when exposed to high temperatures.

[Example J] Next, the present invention will be explained in more detail based on Examples and Comparative Examples.
The invention is not limited to these examples.

Note that the physical properties of the molded products shown in the following examples were measured by the method described below.

(a) Heat distortion temperature; Compliant with JIS K-7207.

(3) Volume resistivity; The resistance value between 1001 and 1001 of a test piece of 12.7 va×12.7+*m×127 mm was measured and calculated.

(4) Electromagnetic wave shielding ability: Measured inside a coaxial transmission pipe. That is, the thickness is 3mm
A test piece in which a hole with a diameter of 251,111 mm was formed concentrically in the center of a disk with a diameter of 90 mm was installed in a coaxial transmission pipe, and the input and output of electromagnetic wave intensity was measured.

Furthermore, the stainless steel fibers used in the following examples have the following characteristics.

5t JS304 fiber bundle: "Naslon" chopped strand manufactured by Nihonma #l Co., Ltd.

iJT diameter 8μm SUS304 stainless steel #& guarantee 5
000 fibers were bundled with polyethylene terephthalate of 12.5% by weight per fiber bundle, and the bundled long fibers were cut into lengths of 5I, SUS316La fiber bundles: manufactured by Nihonma jQ Co., Ltd. Nasron” Chopped Strand.

Approximately 5,000 SUS31 F3L stainless steel fibers with a diameter of 8μ are bundled with polyethylene terephthalate of 12.5% by weight per am bundle, and the bundled length am is cut into lengths of 511II.

Examples 1 to 5, Comparative Examples 1 to 3 Tufflex 410 (trade name, ABS resin manufactured by Mitsubishi Monsanto Chemical Co., Ltd.) and SUS304 spliced bundle or S
US316L1M fiber bundles are blended in the proportions shown in FL Table 1 (in Table 1, the numbers within 0 mean the proportions of stainless steel and fibers excluding the sizing agent), and 4011 - Single-wheel extruder with φ vent (Isuzu Kakoki (
Melt and mix using Full 7 Light Extrusion W1) manufactured by Co., Ltd.
Eight types of pellets with a diameter of 4 ass and a length of about 8 cm were obtained.

Next, using these pellets as raw materials, an injection molding machine (Model 15-9QB manufactured by Toshiba Machinery Co., Ltd.) was used to mold ordinary A B
A test piece was molded under the molding conditions of S a (fat). Using the test piece for each physical property measurement, each p
A Physical properties were measured.

In determining the physical properties of molded products, the heat distortion temperature and Fizotte impact strength were measured on the test piece before heat cycle treatment, and the volume resistivity and electromagnetic shielding ability were measured on the test piece before heat cycle treatment and the test after heat cycle treatment. Measurements were made for each piece.

Here, heat cycle treatment means that the test piece after molding is
One cycle is 1 hour at 85°C, 1 hour at 23°C, 1 hour at -30°C, and 1 hour at 23°C, and this is repeated 10 times, which means that the temperature was changed. .

These measurement results are shown in Table 1 together with the blending ratio.

From Table 1, the following is clear.

(a) A molded article obtained from the conductive thermoplastic resin composition according to the present invention exhibits excellent conductivity and electromagnetic wave shielding ability not only at room temperature but also when subjected to repeated severe temperature changes. (Examples 1-5).

Claims (1)

[Claims] Thermoplastic resin (a) and SUS304 stainless steel fiber (
b) in a proportion of 4 to 15% by weight of component (b) relative to the total amount of component (a) and component (b);
The SUS304 stainless steel fiber (b) is characterized in that it has an average fiber diameter of 2 to 20 μm, an average fiber length of 0.5 to 10 mm, and an aspect ratio of 200 to 1000.
Conductive thermoplastic resin composition.