JPS6392672A - Conductive thermoplastic resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which gives a molded article having stable conductivity and excellent electromagnetic wave shielding ability even after repeated heat cycles, by incorporating specified SUS304 stainless steel fibers and specified short metal fibers in specified weight proportions into a thermoplastic resin. CONSTITUTION:A thermoplastic resin (A) (e.g., a polystyrene) is mixed with SUS304 stainless steel fibers (B) having an average fiber diameter of 2-20mum, an average fiber length of 0.5-10mm, and an aspect ratio of 200-1,000, and short fibers (C) having an average fiber diameter of 10-100mum, an average fiber length of 0.7-7mm, and an aspect ratio of 200 or less and comprising metal fibers (e.g., aluminum fibers) and/or metal-coated fibers (e.g., nickel-coated glass fibers), in such proportions that component B comprises 2-15wt% and component C comprises 3-25wt% based on the total of components A, B, and C, the giving an objective conductive thermoplastic resin composition.

Description

[Detailed description of the invention] "Industrial application field" The present invention relates to conductive thermoplastic Frrt compositions.

More specifically, it relates to a conductive thermoplastic $3 (Jll'1 composition) suitable for producing molded products that exhibit stable conductivity and excellent electromagnetic shielding ability even after undergoing heat cycles.

1"Prior art 1 In recent years, with the rapid spread of electronic equipment, a new social problem of electromagnetic interference has arisen. Namely, office equipment,
Electronic devices such as electronic calculators 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, which can cause interference with other electronic devices. give. Due to these unnecessary electromagnetic waves,
Interference between electronic devices is called electromagnetic interference.

Countermeasures 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 prevent the intrusion of unnecessary electromagnetic waves coming from outside. There are secondary means.

However, electronic equipment has changed from IC to LSI, and furthermore, V l
, SI continues to become faster and more powerful, so the generation of unnecessary electromagnetic waves is even on the rise.
-Next methods naturally have their limits.

Therefore, expectations are very high for unnecessary electromagnetic wave shielding technology as a secondary means, 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, design, freedom of coloring, and easy kickability of molded products.However, since normal thermoplastic resins are electrical insulators, , has no electromagnetic shielding ability at all.

Against this background, studies have been conducted on thermoplastic O (resin casings) with electromagnetic wave shielding ability, and technologies have been developed to make thermoplastic resin molded products with conductive surface treatment, and thermoplastic resin casings with electroconductive Techniques have been proposed to produce molded products made of plastic resin compositions.

However, these conventionally proposed techniques have the following drawbacks.

First, there are technologies to make thermoplastic resin molded products with conductive surface treatment, such as coating the surface of the molded product with conductive paint or spraying zinc or aluminum to form a conductive coating layer. It has been known. However, in order to obtain these thermoplastic resin molded products whose surfaces have been treated to be electrically conductive, a new process is added to form a coating layer of a conductive material on the surface of the molded product, and this process is ! When used as a casing for a 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, as a technique for imparting conductivity to thermoplastic resin, conductive fillers such as metal powder, charcoal It is known that it has become

However, this type of conductive thermoplastic resin composition obtained by conventional techniques has insufficient conductivity and electromagnetic wave shielding ability unless it contains a large amount of conductive filler.
On the other hand, those containing a large amount of conductive filler have the problem of impairing the physical properties of the thermoplastic resin composition, worsening its moldability, and further resulting in poor mechanical properties of the resulting molded product. .

In addition, although conventional molded products made of conductive thermoplastic resin exhibit almost satisfactory conductivity and electromagnetic wave shielding ability under normal conditions, for example, when tan changes between 0°C or lower and 70'C or higher, However, when subjected to continuous heat cycle treatment, the conductivity is gradually lost and the electromagnetic wave shielding ability is insufficient, and from this point of view as well, it cannot be said to be satisfactory.

[Problem to be Solved by the Invention 1] Therefore, in view of the above-mentioned problems of the prior art, the present inventors have found that a molded product with good moldability and excellent mechanical properties can be obtained, and that this molded product can be subjected to severe stress. The present invention was completed as a result of intensive research to provide a conductive thermoplastic O (fatty acid) that exhibits stable conductivity and excellent electromagnetic shielding ability even when subjected to heat cycle treatment. .

[Measures for solving the problem 1'i1 However, the gist of the present invention is that thermoplastic resin (
a), containing SUS304 stainless steel fiber A11 (+1) and short metal fibers and/or metal-coated short fibers (c), component (b) relative to the total amount of component (a), component (b), and component (c). The ratio is in the range of 2 to 15%,
(c) I#, the proportion of minutes is in the range of 3 to 25% by weight,
1 Portrait S tJ S 304 people Stainless fiber AI1. (1
)) is an average fiber diameter of 2'20 μm and an average fiber length of 0.5
・S10ImIn and aspect ratio is 200-100
0, t-, rl, the metal-covered short fibers and metal-coated short fibers (c) have an average fiber diameter of 10 to 100 μm, an average fiber length of 0.7% 7 mm, and an aspect ratio of 2.
A conductive thermoplastic resin composition characterized in that the conductive thermoplastic resin composition has a conductive thermoplastic resin composition of less than 0.00.

The present invention will be explained in detail below.

The conductive thermoplastic (j) resin composition according to the present invention has a thermoplastic resin (a) as a base.
(The resin (a) may be any thermoplastic resin that is normally used as a molding material, and there are no particular restrictions.1゜Specifically,
For example, polystyrene, high impact polystyrene, A S
Styrenic resins such as Jjllm and ABS resins; Olefin ↑h (fats) such as polyethylene and polypropylene; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polyamide O (
Examples include resins, polycarbonate resins, vinyl chloride resins, and blends of these resins.

According to the experiments conducted by the present inventors, the conductive filler to be added to the above-mentioned thermoplastic resin (a) serving as the base together with the metal short fibers and/or still metal-covered short M fibers (C) described below is as follows:
Stainless steel fibers made of SUS304 stainless steel are much better than stainless steel fibers made of other stainless steels such as SUS31G stainless steel, and the purpose of the present invention is achieved by incorporating 5t JS304 stainless steel fibers having the shape characteristics described below. I found out that it can be done.

According to the experiments of the present inventors, furthermore, S tJ S 3
04 stainless steel a fiber (b) is JIS G-4303
It is made of SO8304 stainless steel specified in 8 to 8, with an average fiber diameter of 2·s 20 μm, preferably 4 to 12 μm, and an average fiber length of 0.5 to 10 mm, preferably 2 to 10+sm,
and aspect ratio <m fiber diameter divided by fiber Mt diameter) is 2
To 00, 1000 preferably 200□y 7 (')
It was found that one having a characteristic of 0 is good.

If the average fiber M1-diameter of SUS304 stainless steel fiber (b) is less than 2 μr, the strength of the fiber itself will be insufficient, and when blending this stainless steel fiber into the base thermoplastic & (a), thin stainless steel Ja#F: It is difficult to uniformly disperse the stainless steel fibers on the substrate because they tend to get entangled with each other and become pill-like, and the stainless steel fibers break during the dispersion operation, making it difficult to impart sufficient conductivity to the molded product obtained from the composition. I can't. Furthermore, if the average fiber ME diameter is 20μ+6 or more, the efficiency of imparting conductivity per weight f of the stainless steel #& fiber is low, and the conductive thermoplastic 0 (fat group 1& The molded product obtained from the product has poor surface smoothness and is not practical.

If the average fiber length of the 5tJS 304 stainless steel fiber (b) is 0.5 In1s or less, the aspect ratio will be small, and the molded product obtained from the composition will have sufficient conductivity! It is impractical as it cannot be tested. In addition, if the average fiber length is 1oIO+a or more I-, when blending the second stainless steel fiber into the base thermoplastic resin (a), it is difficult to uniformly disperse the long stainless steel fibers because they tend to get entangled with each other and become pill-like. Molded products obtained from conductive thermoplastic resin compositions containing this stainless steel vLML have poor surface smoothness and are not practical.

Also, SUS 304 stainless steel fiber, 14t(b)
If the aspect ratio is smaller than 200, the efficiency of imparting conductivity and electromagnetic shielding ability to the molded product obtained from the composition is low and impractical, and if the aspect ratio is larger than 1000, the stainless steel kI&IT is When blending with O (fat (a)), the long and thin stainless steel fibers tend to get entangled with each other and form pill-like shapes, making it difficult to uniformly disperse the fibers onto the substrate. The molded product obtained from the composition may be damaged and damaged, making it impractical to provide sufficient conductivity and electromagnetic shielding ability.

ノ, (S blended into the thermoplastic tJim(a) that forms the body)
US304 stainless steel fiber (1) is rated as 1. if it has the characteristics listed below. +tt WL The fibers may be in the form of fibers or in a bundled state, but the latter is preferable in consideration of the kneading operation into the thermoplastic resin (a). Here, the fiber in the Kaito state refers to a plurality of monofilament S (l 8304 stainless steel fibers) having the above-mentioned average fiber diameter, and several hundred fibers for six shells. A so-called chopped strand V-shaped product is obtained by bundling 100 fibers together, converging them using a sizing agent, and cutting this bundle of navy blue fibers to have the above-mentioned characteristics such as average fiber length and aspect ratio. means.

Single-filament SUS304 stainless steel fibers can be used as a sizing agent when sizing fibers, as it has compatibility with the base thermoplastic 04 resin (n) and has a lower melting point than this. There are no restrictions as long as it is a 04 fat that does not inhibit. Such sizing agents can be used in the form of solutions or emulsions.

The conductive thermoplastic υ (fat composition) according to the present invention is
The above S t, J S 304 stainless steel fiber (b),
Menji thermoplasticity! 44 fat (a), SUS304 stainless steel fiber (b), metal short fiber and/or metal covering 1 short YLM\, (C) total type, 4.15
It is necessary that the content be within a range of % by weight.

The above SUS 304 stainless steel V1. If the content of fiber (b) is less than 4%, the molded product obtained from the composition will have insufficient conductivity and electromagnetic shielding ability, making it impractical. %, there is no significant improvement in both the conductivity and electromagnetic shielding ability of the molded product.
1], and furthermore, it deteriorates the moldability of the composition and impairs the original physical properties of the thermoplastic 111 (II\Ha) that serves as the base, which is not preferable.

Component (c) in the present invention consists of Group 8 short fibers, metal-coated short fibers, or a mixture thereof, and has an average fiber diameter of 10
~100μ rings, average ylL fibers of 0.7 x 7 pairs, and aspect ratio of less than 200, preferably 10 or more and less than 200.

Specific examples of the component (c) in 1- are metal fibers made of aluminum, aluminum alloys, copper, copper alloys, iron, iron alloys, etc., or the surface of non-penetrating fibers such as lath fibers 7 and carbon fibers. Metal coated kl&dark blue, which is formed by disposing a metal coating made of aluminum, zinc, copper, nickel, silver, etc., on the surface of the metal and has the above-mentioned shape characteristics can be mentioned.

When the average fiber diameter of component (c) is 10 μIll or less and the average fiber length is 0.7 ml or less, the efficiency of imparting conductivity is low, so the molded product obtained from this composition will not have sufficient electromagnetic wave shielding ability. It will not be effective and is not practical. Also, Yuyun #! iL fiber diameter is 100μω or more1
- or when the average length is 7 mm or more than 11 m, the molding processability of this composition will not only deteriorate, but the surface smoothness of the resulting molded product will be poor. Therefore, it is not practical.

In addition, when the 7-spectral ratio of the component (c) is 200 or more, the component (c) and the SUS304 stainless steel fibers become intertwined when dispersed in the thermoplastic resin that serves as the base material.
This is not preferable because the dispersibility deteriorates. Furthermore, those having an aspect ratio of less than 5 are undesirable because the efficiency of imparting conductivity and electromagnetic wave shielding ability to a molded article obtained from the composition is low.

Component (c) in the present invention, that is, the short metal fibers and/or the metal-coated short fibers, may be in the form of short fibers, or may be a plurality of short fibers bundled with resin.

And, the conductive thermoplastic Of fat composition according to the present invention has 1
- Component (c) is the thermoplastic +34 fat (a), SU
It is necessary that the content be 3 to 25% by weight based on the total amount of S304 stainless steel i41 [1)) and component (c).

If the content of component (c) is less than 3% (11:%), the conductivity and electromagnetic wave shielding ability of the molded product obtained from the composition when subjected to heat cycle treatment will decrease, The purpose of the present invention cannot be achieved, and if it exceeds 25% by weight, the molding processability of the composition will deteriorate and the original physical properties of the thermoplastic 04 fat (a), which is the base material, will be impaired. Undesirable.

In order to prepare the conductive thermoplastic resin composition according to the present invention, the thermoplastic resin (a), S U having the above characteristics
Dry planing the S 304 stainless steel fiber AM (b) and the above-mentioned fibers and/or metal-coated iσ woven fibers c) using a Henschel mixer, or dry-blending the same with a Henschel mixer or Banbury mixer. It is possible to adopt a method of dispersing cross-wires by using T8 fused mixed iso such as -, Niegoo, single-sleeved extruded iso, and Nitsumugi extruded iso.

In order to smoothly perform this tri-blend treatment and cross-dispersion operation, SUS 304 stainless steel fiber a (+
] > and Kinkutantan NILMt t; upper/main C earth order belonging to t. During operation and cross-dispersion operation, the fibers do not fly away, so it is possible to prevent the working environment from deteriorating.

Further, it is possible to further reduce entanglement and breakage of fibers during the kneading process, and it is possible to impart excellent conductivity and electromagnetic wave shielding ability to a molded article obtained from the composition, which is preferable. In addition, when using WL navy blue in a focused state, the pure content of SUS 304 stainless steel [1] and inorganic fiber excluding the resin impregnated and attached to the focused fibers is as follows: It is necessary to determine the charge combination of the focused i-fibers so that it falls within the range specified in i1.

The conductive thermoplastic resin composition according to the present invention includes the above ([
In addition to component I), component (b), and component (c), flame retardants, colorants, plasticizers, ultraviolet absorbers, lubricants, heat stabilizers,
This can be done by incorporating anti-static agents and various other resin additives.

The conductive thermoplastic resin composition according to the present invention can be used as a manufacturing material for various electronic device casings, integrated circuit containers, etc., and can also be used as flooring, ceiling, and wall materials for computer rooms, etc. It can also be used as a forming material.

1゛Effects of the Invention 1 The present invention has the contents as explained in detail below-1〉, and has particularly remarkable effects as follows, so its industrial utility value is extremely high6( 1) The conductive thermoplastic resin composition according to the present invention exhibits good moldability because the content of SUS 304 stainless steel fibers, metal 1u fibers ML and/or metal-coated staple fibers is appropriately selected.

(2) The conductive thermoplastic resin composition according to the present invention can be manufactured by the commonly used tri-blend method and/or cross-dispersion method, so no special equipment or special process is required for manufacturing. First, it is easy to prepare.

(3) The conductive thermoplastic resin composition according to the present invention uses SUS304 as a filler, which has the characteristics specified in the present invention.
Since it contains stainless steel fibers and metals wLM and/or metal-coated short fibers, S as a conductive filler
Despite the low content of US 304 stainless steel fibers, molded articles obtained from this composition exhibit excellent electrical conductivity and electromagnetic shielding ability.

(4) The molded article obtained from the conductive thermoplastic 04 resin composition of the present invention exhibits good conductivity and electromagnetic wave shielding ability under normal conditions, and even when subjected to severe changes in temperature conditions (heat cycle). Shows stable and good conductivity and electromagnetic wave shielding ability.

[Example 1] Next, the present invention will be explained in more detail based on Examples and Comparative Examples.
It 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.

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

(2) Izot impact strength: Compliant with J Is K-7mm10 (with tick).

(3) Volume resistivity; 12.7+a+aX 12.7mmX 127+111
The resistance value between 100 ++ ua of the test piece No. 6 was measured and calculated.

(4) Electromagnetic wave shielding ability: Measured by the coaxial transmission line method. That is, thickness 3II
II111 A test piece in which a hole with a diameter of 25+ am was formed solidly and concentrically in the center of a disk with a diameter of 90+ am,
It was installed inside a coaxial transmission pipe and measured the input and output of electromagnetic wave intensity.

In addition, the stainless steel fibers, metal short fibers, and metal-coated short fibers used in the following examples had the following characteristics.

(1) Stainless steel #a fiber s u 8304 aV Lt4)+: "NASLON" Titanobutsu strand manufactured by Nippon Seisen Co., Ltd.

SO8304 stainless steel old OL with a diameter of 23μm approx. 500
After converging 0 fibers with polyethylene terephthalate of 12.5% polydispersity per vL fiber bundle,
Cut the accent to length 5InI11.

(2) Metal 1σ fiber and metal coated pheasant fiber a brass HL & navy blue: manufactured by Aisin Seiki Co., Ltd., Aisin Metal 7 Eyeper.

Average fiber diameter 60μm prepared by chatter cutting method
, brass fiber with an average fiber length of 3+I1 m.

Aluminum fiber: Aisin Metal Fiber manufactured by Aisin Seiki Co., Ltd.

Prepared by chattering cutting method, average abrasive diameter 60μ
Aluminum fiber with average line 4U 3τ01.

Nickel coated glass fiber: Manufactured by Asahi Fiberglass Co., Ltd., Ni coated lath fiber mX
EM-1,00゜Diameter 23μl double gamma Kel plating〃Russei fiber approx. 3000
After books are bundled with a resin binding agent containing 10% heavy electric current per fiber bundle, the bundled long fibers are cut into lengths of 3+a+n.

Example 1.3.5.7 Tufflex 410 (trade name, Mitsubishi Monsanto (t, +
&(4UW, ABSlfJlt, SUS304#a
, J4j bundle t3 and brass fibers are shown in Table 1, respectively. j combination (fj In the S1 table, the numbers within 0 exclude the sizing agent (meaning the proportion of stainless steel Ja, stt only). , melted using a full-flight extrusion method) 11, diameter 4 + Il + a, Ex approximately 8
11) 4 types of bullets of In+n.゛Next, using these pellets as raw materials, injection molding (manufactured by Toshiba Machinery Co., Ltd., Model 1S-90B) is used to mold ordinary AB.
A test piece was molded under the molding conditions of S resin.

Various physical properties of the obtained test piece were measured according to the above method.

In addition, in measuring the physical properties of molded products, the heat distortion temperature and Fizot impact strength were determined by heat cycle treatment J+I! The volume resistivity and electromagnetic wave shielding ability were measured for the test piece before heat cycle treatment and the test piece after heat cycle treatment.

Here, the heat cycle treatment means that the test piece after molding is
1 hour at 5℃, 1 hour at 23℃, 1 hour at -30℃
One cycle is defined as leaving the sample at 23° C. for 1 hour, and this is repeated 10 times to change the temperature.

The surfaces of the molded products obtained in these Examples were all smooth. The measurement results for each physical property are shown in the first column along with the blending ratio.

Example 2.4.6 In the example described in Example 1, nickel-coated plus fibers (Example 2) and aluminum fibers MF (Example 4.6) were used in place of the brass fibers, and the first Same as in the same example except that it was mixed in the proportion shown in the table.
Three types of pellets having shapes similar to those of the same example were obtained.

Next, using these pellets as raw materials, test pieces were molded in the same manner as in the same example. 1) Various physical properties of the obtained test pieces were measured in the same manner as in the same example.

The surfaces of the molded products obtained in Example t; were all smooth.The measurement results of each physical property were as follows.
They are shown in Table 1 together with 1 go.

Comparative Example 1 The same example as described in Example 1 was used, except that copper fiber was not blended and 8N S resin and SUS3044a fiber bundle were blended in the proportions shown in Table 1. and
A pellet having a shape similar to that of the same example was obtained.

Next, using this pellet as a raw material, a test piece was molded in the same manner as in the same example. Regarding the obtained test piece, various physical properties were measured in the same manner as in the same example. The measurement results are shown in the same 1's1 table along with the blending ratio.

Comparative Example 2.3 In the example described in Example 1, SUS 3041&
11) Two types having the same shapes as in Example 11) were prepared in the same manner as in the same example except that the navy blue bundle was not blended and A B S +33 fat and aluminum fiber were blended in the proportions shown in Table 1. got a beret.

Next, using these pellets as raw materials, test pieces were molded in the same manner as in the same example. Regarding the obtained test piece,
Various physical properties were measured in the same manner as on the ipsilateral side. The respective measurement results are also shown in Table 1 along with the blending ratio.

The following is clear from the first person.

(1) The molded product obtained from the conductive thermoplastic composition of 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. (Go to Example 1/7).

(2) Molded products obtained from compositions that do not contain metal fibers and/or metal coating [A fibers, which are essential requirements in the present invention, will decrease in conductivity and electromagnetic wave shielding ability when subjected to repeated temperature changes. (Comparative Example 1).

(3) The conductive thermoplastic rubber (IR, - molded product obtained from the resin composition) according to the present invention is made of expensive SUS304Jil [which is derived from a composition containing a relatively low electrical charge in the bundle]. However, it exhibits a practical level of conductivity and electromagnetic wave shielding ability not only at room temperature but also after repeated severe temperature changes (Examples 3 to 7).

(4) Molded products obtained from compositions that do not contain SUS 304 stainless steel fibers, which are essential requirements in the present invention, exhibit practical levels of conductivity and electromagnetic wave shielding ability at room temperature, but cannot be subject to repeated temperature changes. As a result, the conductivity and electromagnetic wave shielding ability are significantly reduced, making it impossible to put it into practical use (Comparative Example 2.3).

Patent applicant: Mitsubishi Monsando Kasei Co., Ltd. Fii
Person Patent Attorney Atsuya - (1 idiot)

Claims (1)

[Claims] Thermoplastic resin (a), SUS304 stainless steel fiber (b)
) and metal short fibers and/or metal coated short fibers (c
), the ratio of component (b) to the total amount of components (a), (b) and (c) is in the range of 2 to 15% by weight, and the ratio of component (c) is in the range of 3 to 25% by weight. The SUS304 stainless steel fiber (b) 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, and Fiber (c) has an average fiber diameter of 10
100 μm, an average fiber length of 0.7 to 7 mm, and an aspect ratio of less than 200.