JP2000290514A - Conductive resin composition and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproducibly obtain a composition, which has a desired volume resistivity within a specified range, by using a fibrous filler of high conductivity having a specific volume resistivity and a fibrous filler of low conductivity in combination and specifying a total amount thereof relative to a thermoplastic resin. SOLUTION: A fibrous filler of high conductivity having a volume resistivity of 10-3 Ω.cm or below and a fibrous filler of low conductivity having a volume resistivity of 100 to 103 Ω.cm are compounded in a thermoplastic resin, and the total content of the fibrous fillers is 15 wt.% or below. The resultant resin composition has a volume resistivity ranging from 101 to 108 Ω.cm. For the manufacture of the composition, the components to be compounded are kneaded in a single screw extruder. A preferred fibrous filler of high conductivity includes stainless steel fibers, nickel-coated fibers or graphitized carbon fibers. As the fibrous filler of low conductivity, mention is made of PICH-based carbon fibers sintered at a low temperature. The thermoplastic resin includes an olefin resin, an ABS resin, a styrene resin or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an antistatic or antistatic resin composition. More specifically, the present invention relates to a method for producing a conductive resin composition having a desired volume resistivity.

[0002]

2. Description of the Related Art Heretofore, a conductive resin composition having a desired volume resistivity has been obtained by blending a conductive filler having a volume resistivity lower than that value with a thermoplastic resin. In order to obtain a conductive resin composition having a lower volume resistivity, it was necessary to mix more conductive filler.

[0003] The form of the conductive filler is granular, flake, fibrous, and the like. Among them, the fibrous filler is effective in imparting conductivity with a small amount, and is widely used.

[0004]

However, as the mixing ratio of the fibrous conductive filler increases, kneading becomes more difficult and a large kneading force is required. In particular, when an ABS resin is used as the thermoplastic resin, the viscosity tends to increase in a processing machine, so that the melt-kneading operation is more difficult.
Therefore, even if a strong kneader such as a twin-screw extruder is used, it is difficult to uniformly disperse the fibrous conductive filler.However, the fibrous conductive filler is sheared by the strong kneading action, and the fiber length is shortened. When the conductive resin composition is manufactured, a large amount of the conductive filler must be blended in advance in predicting an increase in the volume specific resistance value due to the fiber length defect when manufacturing the conductive resin composition.

[0005] Above all, in the range of 10 ¹ to 10 ⁸ Ωcm, where the volume resistivity is not so low, it often occurs that the desired value is deviated by more than 10 1 or 2, or the same composition. Even if it was manufactured in a ratio, the value varied from batch to batch, and the reproducibility of the volume resistivity in the manufacture of the conductive resin composition was very poor. As the compounding ratio of the fibrous conductive filler is increased to solve this, the volume resistivity of the molded product is stabilized,
It will be lower than the desired value. Since the desired specific volume resistivity cannot be obtained and the volume specific resistance cannot be adjusted by adding a filler or a resin again to the conductive resin composition, the production is repeated from the beginning, and the productivity is poor. There was a problem.

[0006]

That is, a first aspect of the present invention provides a fibrous high conductive filler having a volume resistivity of 10 ⁻³ Ωcm or less, and a fibrous low conductive filler having a volume resistivity of 10 ⁰ to 10 ³ Ωcm. A conductive resin composition comprising a thermoplastic resin mixed with a conductive filler, wherein the total content of the fibrous filler is 15% by weight or less and the volume resistivity is in the range of 10 ¹ to 10 ⁸ Ωcm.

In the second invention, the volume resistivity is 10 ^-3 Ω.
The conductive resin composition according to the first aspect, wherein the fibrous highly conductive filler having a diameter of not more than 1 cm is stainless steel fiber.

According to a third aspect of the invention, the volume resistivity is 10 ^-3 Ω.
The conductive resin composition according to the first aspect, wherein the fibrous highly conductive filler having a size of not more than 1 cm is a nickel-coated fiber.

According to a fourth aspect of the present invention, the volume resistivity is 10 ^-3 Ω.
The conductive resin composition according to the first invention, wherein the fibrous highly conductive filler having a size of not more than 1 cm is a carbon fiber formed into graphite.

According to a fifth aspect of the present invention, the volume resistivity is 10 ^-3 Ω.
cm or less, and a volume specific resistance value of 10 ⁰ to 10 ³ Ωcm is mixed with a thermoplastic resin and kneaded with a single screw extruder. Total content of fibrous filler is 15% by weight
The method for producing a conductive resin composition according to the first invention, wherein the following volume specific resistance is in a range of 10 ¹ to 10 ⁸ Ωcm.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The fibrous highly conductive filler used in the present invention,
Those having a volume resistivity of 10 ⁻³ Ωcm or less are shown. Examples of the fibrous high conductive filler include a metal fiber, a carbon fiber which has been baked at a high temperature to be graphitized, a metal-coated fiber, and the like.

As the metal fiber, for example, pure iron, carbon steel,
Examples include metal fibers such as stainless steel, copper and copper alloys, aluminum and aluminum alloys, nickel and nickel alloys, gold, and silver, and stainless steel fibers having excellent corrosion resistance are particularly preferable.

As the metal for coating the metal-coated fiber, nickel which is resistant to acid and alkali is particularly preferable. Examples of fibers to be coated include carbon fibers, glass fibers, and organic fibers such as polyamide fibers, and these may be surface-treated. In particular, carbon fibers and polyamide fibers are good because they have good metal adhesion and do not fall off the metal.

Examples of the carbon fiber which has been graphitized by firing at a high temperature include PAN (polyacrylonitrile)
Carbon fiber.

Stainless steel fibers and nickel-coated organic fibers have a desired volume resistivity of mainly 10 ² Ωcm or less, and nickel-coated carbon fibers have a desired volume resistivity of mainly 10 ⁴ Ωcm or more. The desired volume specific resistance value of the graphitized carbon fiber is 1
It is particularly desirable to use it at a resistivity of 0 ³ Ωcm or more.

This is because the specific gravity of each of the fibrous highly conductive fillers is different, so that even if the fibrous highly conductive fillers are blended at the same weight, their bulk and surface area are different. Therefore, even if the fibrous high conductive filler having the same length, diameter and volume specific resistance is blended at the same weight, the finally obtained conductive resin composition has different volume specific resistance.

For example, since carbon fibers having a small specific gravity have a large surface area per unit weight, and metal fibers having a large specific gravity have a small surface area per unit weight, even if fillers having the same length, diameter and volume resistivity are used, In order to obtain the same volume specific resistance, the carbon fiber requires a smaller blending weight.

Further, since the properties of the fibers of each fibrous highly conductive filler are also different, for example, carbon fibers are weaker in physical force such as kneading than metal fibers or organic fibers, and the fibers are easily broken. It is not very suitable to use carbon fibers to obtain a conductive resin composition having a relatively low volume resistivity.

The length of the fibrous highly conductive filler is 2 to 4 m.
m and the diameter are preferably from 6 to 12 μm. If the length is less than 2 mm, the fiber length is further shortened during kneading, so that it becomes difficult to obtain excellent conductivity with a small amount, which is not preferable.
If it exceeds 4 mm, the shape of the pellet may be defective, or the fluidity of the resin may be impaired, which may make it difficult to fill the mold at the time of molding. This is not preferred because

In general, a smaller diameter is preferable because the surface area of the filler per unit weight is increased.
If it is less than this, the bulk becomes relatively bulky and the cost increases, which is not preferable. On the other hand, if the thickness exceeds 12 μm, the surface of the molded article becomes rough, the smoothness is lost, and the surface appearance is poor.

The mixing ratio of the fibrous highly conductive filler to the thermoplastic resin varies depending on the desired volume resistivity.
-7% by weight is preferred, and 1-4% by weight is particularly preferred.
Further, the ratio is preferably smaller than the mixing ratio of the fibrous low conductive filler. This is because the adjustment of the volume specific resistance value is mainly performed by the fibrous high conductive filler, but the fine adjustment depends largely on the fibrous low conductive filler.

Examples of the fibrous low conductive filler used in the present invention, volume resistivity 10 ⁰ to 10 ³ [Omega] cm for P
ICH-based low-temperature fired carbon fibers may be used.

The fibrous low conductive filler also desirably has a fiber length and a fiber diameter substantially equal to those of the fibrous high conductive filler. This is because, in addition to the reasons for the fiber length and fiber diameter of the fibrous highly conductive filler, when the fillers in the thermoplastic resin have substantially the same size, they can be uniformly dispersed during kneading.

The fibrous low conductive filler can finely adjust the volume specific resistance value, uniformly disperse the fibrous high conductive filler in the thermoplastic resin, and prevent breakage and cutting of the fibrous high conductive filler fiber. It seems to have played a supplementary role.

The mixing ratio of the fibrous low conductive filler to the thermoplastic resin varies depending on the desired volume resistivity.
８8% by weight is preferable, and more preferably the mixing ratio of the fibrous highly conductive filler is higher.

The mixing ratio of the fibrous high conductive filler and the fibrous low conductive filler to the thermoplastic resin is appropriately determined according to the desired volume resistivity. Only the fibrous high conductive filler or the fibrous low conductive filler is used. Only the filler is not mixed with the thermoplastic resin, but the two fillers are always mixed to obtain the conductive resin composition.

The total content of the fibrous filler composed of the fibrous high conductive filler and the fibrous low conductive filler in the conductive resin composition of the present invention is preferably 15% by weight or less, more preferably 10% by weight or less. % By weight or less is desirable. 1
If it exceeds 5% by weight, it becomes difficult to knead,
It becomes very difficult to obtain a desired volume resistivity, in particular, 10 ⁶ to 10 ⁸ Ωcm. Further, the fibrous high conductive filler and the fibrous low conductive filler may be blended one by one or in combination of more kinds.

Since the total content of the fibrous filler in the conductive resin composition is suppressed to a low concentration of 15% by weight or less, a strong dispersion for uniform dispersion of the fibrous filler in the thermoplastic resin is obtained. Since no kneading is required, a relatively weak kneading force of a single-screw extruder is sufficient. Therefore, the shearing degree of the fiber length of the fibrous conductive filler is reduced, and as a result, the conductive resin composition is suppressed to a range of ± 10 ¹ Ωcm from the desired volume resistivity or batch-to-batch volume resistivity. Things are obtained.

As the thermoplastic resin used in the present invention, olefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, acid-modified olefin resin, impact-resistant polystyrene, ABS resin and styrene-butadiene copolymer are used. Styrene resin such as coalescence, or polycarbonate resin, polyketone resin,
Examples thereof include polyester and polyamide resins and a mixture of one or more of them.

In order to minimize the shearing of the fibers of the fibrous conductive filler and the resulting deviation of the volume resistivity, the kneading time is desirably minimized.

Since the volume specific resistance value depends on the fiber length of the fibrous conductive filler, etc., the production of a molded article made of the conductive resin composition should be carried out by using the fibrous conductive filler and the thermoplastic resin pellet. A method of directly injection molding a premix of the above is desirable. However, from the viewpoint of uniform dispersibility of the filler and ease of handling as a molding material, a compound type in which the filler is previously mixed in a thermoplastic resin is excellent. In particular, in the form of a pellet, handleability is good and productivity is improved.

Further, the conductive resin composition of the present invention is blended with a heat resistance, a weathering agent, a lubricant, a slip agent, a flame retardant, a nucleating agent, a pigment, a dye, etc. within a range not to impair its function. You may use it.

In the present invention, in order to produce a conductive resin composition, a fibrous high conductive filler, a fibrous low conductive filler and a thermoplastic resin are melt-kneaded by a single-screw extruder.
The mixture can be extruded into strands and pellets can be obtained using a pelletizer.

Now, the present invention will be described in further detail with reference to Examples. However, the present invention is not limited in any way by these examples.

[0035]

The evaluation methods used for the examples and comparative examples are as follows. 1) Pellet moldability: Pellet moldability of the conductive resin composition subjected to melt-kneading. A good result was obtained when pellet molding was possible, and a bad result was impossible when pellet molding was impossible. 2) Volume specific resistance value: 75 m of a molded product having a size of 50 mm × 75 mm × 3 mm obtained by injection-molding the conductive resin composition.
A silver paste (Silcoat RL-10, manufactured by Fukuda Metal Foil & Powder Co., Ltd.) is applied to two sides of mx 3 mm, and the electric resistance value is measured using this part as an electrode. Equation for calculating volume resistivity γ = 4.5 × R (where γ is the volume resistivity, R
Indicates an electric resistance value, and 4.5 indicates a count based on the shape. ) Was substituted for the electric resistance value to determine the volume specific resistance value γ.

3) Dispersibility; volume resistivity value is 10 ¹ to 1
In the range of 0 ⁸ [Omega] cm, to produce a conductive resin composition was examined whether uniform volume resistivity in a batch is obtained (dispersion stability). 5 per batch
The volume resistivity of each of the plate-shaped molded articles was measured, and the difference between the average value of the five plates and the volume resistivity of each plate was within the range of 10 ± 1 (for example, the desired volume resistivity). Is 1 × 10 ³ Ωcm, 1 × 10 ² to 1
(In the range of × 10 ⁴ Ωcm), it is determined that the conductive filler is uniformly dispersed in one batch of the conductive resin composition, and it is determined that there is dispersibility. In this case, it was judged as NG because there was no dispersibility.

4) Reproducibility; volume resistivity value of 10 ¹ to 1
In the range of 0 ⁸ [Omega] cm, the conductive resin composition produced twice, were investigated stable volume whether specific resistance value is obtained (preparation of reproducibility). If the difference between the average values of the volume resistivity values of the first and second batches falls within the range of 10 ± 1 power, it is determined that there is reproducibility. If it exceeds 10 ± 1 power, there is no reproducibility. NG. 5) Surface abrasion: 100 g of copy paper (PPC paper) with a weight placed on the surface of a molded product obtained by injection-molding a conductive resin composition, and reciprocated 500 times at 50 mm intervals to form a molded product Of the surface of the molded product is visually observed, and when the generation of foreign matter such as fibrous conductive filler is observed on the surface of the molded product, N
G, OK if not done.

Examples 1 to 5 and Comparative Examples 1 to 8 A polypropylene resin, an ABS resin, and a polyketone resin were used as thermoplastic resins, and stainless fibers (2 to 4 mm in length, 8 μm in diameter, Specific resistance 10 ^-5 Ω
cm), nickel-coated carbon fiber (length 6 mm, diameter 8μ)
m, volume resistivity 10 ⁻⁵ Ωcm), nickel-coated aramid fiber (length 6 mm, diameter 12 μm, volume resistivity 1)
0 ^-5 Ωcm), PAN-based carbon fiber (length 6 mm, diameter 7μ
m, volume specific resistance 10 ⁻³ Ωcm), PICH-based carbon fiber (length 4 mm, average diameter 11) as a fibrous low conductive filler
[mu] m, a volume resistivity 10 ⁰ to 10 ³ [Omega] cm, Osaka Gas Co., Ltd., trade name: Zairasu the GC over 03J-401) were blended in proportions shown in Table 1, and kneaded melted using a single-screw extruder, A conductive resin composition was extruded in a strand shape and formed into a pellet using a pelletizer.

Next, an electromultimeter CDM-
Using a 5000 (manufactured by Custom Co., Ltd.), the conductive resin composition was injection-molded with a Toshiba IS100F1 type injection molding machine (manufactured by Toshiba Machine Co., Ltd.), and 50 mm × 75 mm ×
A 3 mm molded product was obtained. The resulting plate was evaluated for its volume resistivity, surface wear, and the like. The results are shown in Table 1.

[0040]

[Table 1]

[0041]

The conductive resin composition of the present invention can be uniformly dispersed by kneading with a single-screw extruder since the total compounding ratio of the fibrous conductive filler is low. , A resin composition having a desired value can be produced with good reproducibility when the volume resistivity is in the range of 10 ¹ to 10 ⁸ Ωcm. In addition, the pellet formability is good, the conductive filler does not fall off even if the surface is rubbed, not only the degree of freedom of coloring of the molded article is greatly increased, but also the physical properties such as the Izod value and elongation of the resin composition can be maintained. As a result, the conductive resin composition of the present invention can be used for packaging various electronic components such as a silicon wafer, an IC, an LSI or a substrate incorporating them and a conductive carrier case or a conductive tray used for transferring semiconductor products. It can be used not only for small parts such as materials, but also for large housings and the like that require mechanical strength.

Claims (5)

[Claims] 1. A volume resistivity 10 ^-3 [Omega] cm or less fibrous high conductive filler and a volume resistivity of 10 ⁰ to 10 ³ Omega
cm of a fibrous low conductive filler in a thermoplastic resin, wherein the total content of the fibrous filler is 15% by weight or less and the volume specific resistance is in the range of 10 ¹ to 10 ⁸ Ωcm. Composition. 2. The conductive resin composition according to claim 1, wherein the fibrous highly conductive filler having a volume resistivity of 10 ⁻³ Ωcm or less is a stainless steel fiber. 3. A fibrous highly conductive filler having a volume resistivity of 10 ⁻³ Ωcm or less is a nickel-coated fiber.
3. The conductive resin composition according to item 1. 4. The conductive resin composition according to claim 1, wherein the fibrous highly conductive filler having a volume resistivity value of 10 ⁻³ Ωcm or less is a carbon fiber made of graphite. 5. A fibrous highly conductive filler having a volume resistivity of 10 ^-3 Ωcm or less, and a volume resistivity of 10 ⁰ to 10 ^3.
A fibrous low conductive filler of Ωcm is blended with a thermoplastic resin and kneaded with a single screw extruder. The volume specific resistance value of the total fibrous filler content of 15% by weight or less is 10 ^1. 2. The method according to claim 1, wherein the range is from 10 to 10 ⁸ Ωcm.
3. The method for producing a conductive resin composition according to item 1.