JPS6160760A - Electromagnetic wave shielding composition - Google Patents

Abstract

PURPOSE:To provide an electromagnetic wave shielding compsn. having an excellent electromagnetic wave shielding effect, by adding an incompletely annealed metallic fiber to a thermoplastic resin. CONSTITUTION:A metallic fiber (A) (e.g. aluminum or stainless steel fiber) annealed at an annealing temp. of 85-95% of complete annealing temp., and pref. 0.1-52pts.wt. metallic compd. (B) (e.g. titanium oxide or ultramarine) selected from among oxides and silicates Group IVa metals, compds. of iron family element, composite oxides composed of two or more metal oxides and zinc oxide, and 0.1-2ps.wt. lubricant (C) (e.g. stearamide or zinc laurate) selected from among fatty acid amides and metallic soaps are added to 100pts. wt. thermoplastic resin (D) (e.g. polypropylene resin or ABS resin) to obtain the desired electromagnetic wave shielding compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a conductive resin composition used for shielding electromagnetic waves, particularly an electromagnetic wave shielding composition that has a better electromagnetic wave shielding effect than conventional electromagnetic wave shielding compositions. It is related to.

[Background of the invention]

In Western countries, housings of electronic devices such as computers, word processors, etc. are often It is mandatory to use equipment that has been treated to shield electromagnetic waves emitted by the equipment.

Electromagnetic wave shielding in electronic equipment as described above will be required sooner or later in Japan (IJI is on the way, and various electromagnetic wave shielding methods are being considered).

Shielding of 1i magnetic waves as mentioned above can basically be achieved by imparting appropriate conductivity to the housing that covers the electronic device, and conventionally, zinc was sprayed on the inner wall of the housing to form a zinc coating. A method of imparting conductivity to the housing, and a method of applying conductive paint to the inside of the housing.
Methods of imparting electrical conductivity to the housing are well known.

Furthermore, it is also known that a conductive material is introduced into the thermoplastic resin that forms the main body of the housing, thereby making the housing itself conductive.

However, in the method of zinc spraying or applying conductive paint to the inner wall of the housing as described above, the manufacturing time is reduced because zinc is sprayed or the conductive paint is applied to the inner wall of the housing that has been formed in advance. In addition, especially in the case of conductive paints, the conductive paint itself is expensive, so there is a drawback that the cost is inevitably high.

In addition, the housing made by mixing conductive material with thermoplastic resin has a volume resistivity of 10, which has a conductivity and electromagnetic wave shielding effect.
-1 to 10-3Ω If you try to hold the housing at the opening, you have to mix a large amount of conductive material, which has the disadvantage of lowering the strength.On the other hand, if you try to manufacture a housing with sufficient strength, Therefore, there is a need for an electromagnetic wave shielding composition that has a good electromagnetic wave shielding effect with a small amount of conductive material added.

[1 Summary of the Invention] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an electromagnetic shielding composition that can produce an electromagnetic shielding product having sufficient strength and conductivity. do.

Therefore, the electromagnetic wave shielding composition according to the present invention is characterized in that incompletely annealed metal fibers are added to a thermoplastic resin.

Furthermore, the second electromagnetic wave shielding composition according to the present invention is prepared by adding incompletely annealed metal fibers to a thermoplastic resin, and adding a periodicity of Na to 100 parts by weight of the thermoplastic resin.
oxides of the group Nax Alx Si〈x2-X)O
zJay O
It is characterized by adding 01 to 52 parts by weight.

Further, the third electromagnetic wave shielding composition according to the present invention includes the addition of incompletely annealed metal fibers to a thermoplastic resin, and the addition of at least 0.1 lubricant selected from the group consisting of fatty acid amides and metal soaps. It is characterized by the addition of ~2 parts by weight.

Furthermore, the fourth composition for shielding electromagnetic waves according to the present invention is obtained by adding incompletely annealed metal fibers to a thermoplastic resin, and at the same time, the thermoplastic resin
oxides of the group NaxAlχSi<12-x)024
One or more metal compounds selected from the group consisting of silicates represented by NaγS, iron group compounds, double oxides with a composite structure of two or more metal oxides, and zinc oxide at 0.1
~52 parts by weight, and 0.1 to 2 parts by weight of one or more lubricants selected from the group consisting of fatty acid amide and gold soap.

According to the present invention, since an appropriate amount of incompletely annealed metal fiber is added, there is an advantage that the electromagnetic wave shielding effect can be improved without reducing the strength of the electromagnetic wave shielding molded product.

Further, according to the second electromagnetic wave shielding composition according to the present invention, in addition to the incompletely annealed metal fibers described above, an appropriate amount of an oxide of group IVa in the periodic table, NaxAlxSi(12-X
>OzJay S Z The addition of one or more metal compounds selected from the group consisting of silicates, iron group compounds, double oxides with a composite structure of two or more gold mud oxides, and zinc oxide increases the strength. Even better electromagnetic wave shielding effects can be obtained without deterioration.

Further, according to the third aspect of the present invention, a lubricant is added together with the incompletely annealed gold ita fibers, thereby achieving an even better electromagnetic wave shielding effect and preventing the formation of fiber balls of the metal fibers. Therefore, the metal fibers can be uniformly dispersed, and a large amount of metal fibers can be added at once. Therefore, there are advantages in that workability is significantly improved and reproducibility is improved.

Furthermore, according to the fourth aspect of the present invention, together with the incompletely annealed metal fibers described above, an appropriate amount of an oxide of group IVa of the periodic table, Nax Alx St(12-x)02
Since a lubricant and one or more metal compounds selected from the group consisting of silicates, iron group compounds, double oxides with a complex structure of two or more gold mud oxides, and zinc oxide, as shown in aNayS a, are added, Not only can a good electromagnetic wave shielding effect be achieved, but also the formation of fiber balls of gold i-fibers can be prevented. Therefore, the metal fibers can be uniformly dispersed,
It becomes possible to introduce a large amount of gold WkuA fiber at once. Therefore, workability is significantly improved and reproducibility is improved.

[Detailed description of the invention]

The present invention will be explained in more detail.

The electromagnetic wave shielding composition according to the present invention is basically a mixture of gold R fibers in a thermoplastic resin, but such thermoplastic resin is not fundamentally limited, and conventional Resins used for housings of this type of electronic equipment can be effectively used. For example, it can be one or more of polypropylene resin, ABS resin, modified PPO resin, polyamide resin, polycarbonate resin, PPS resin, and the like.

The conductive substance used in the present invention is incompletely annealed gold N fiber as described above, but the incompletely annealed gold GUI fiber used in the present invention is manufactured using a manufacturing method that stops work hardening.
For example, aluminum fibers, stainless steel fibers, AI-Mg, AI C, etc. manufactured by chatter vibration cutting method, pultrusion method, etc., and for which incomplete annealing treatment is effective.
One or more types of alloy fibers such as U^1 alloy fibers, Cu alloy fibers such as brass, etc. can be effectively used.

The incomplete annealing treatment according to the present invention is characterized by not completely annealing, but by performing the treatment at a temperature range of 85 to 95% of the complete annealing temperature, so that some work hardening remains. By performing a treatment that leaves only a slight amount of work hardening, it is possible to maintain a good balance of strength and malleability to resist the cutting action in the kneading and injection molding processes, without reducing workability. As a result, the electromagnetic wave shielding hardening of the molded article can be significantly improved.

said temperature is less than 85% of the full annealing temperature;
Because the elongation is insufficient compared to the tensile strength, it is easy to break during the molding process, and if it exceeds 95%, the work hardening does not remain sufficiently, so it is easy to form fiber balls and the dispersibility is poor. This is because it decreases.

For example, aluminum alloy (7) 1050.1100.2o
17.5005.5052.5056 (according to JIS) is 300-350℃, four-hole brass is 410-470℃,
Semi-brass is 420-470℃, stainless steel is 310.3
16L, 403.420 (JIS) is 540-6
20°C is the desired temperature for incomplete annealing. Such incomplete annealing treatment is performed by heating to the above-mentioned predetermined temperature and then allowing it to cool naturally in an inert atmosphere.

The amount of incompletely annealed metal fibers added to the thermoplastic resin according to the present invention is preferably 3 to 25% by volume,
The number of pieces per unit volume is preferably 500 pieces/c
It is a1 or more. If the amount of metal fiber added is less than 3% by volume, there is a risk that sufficient electrical conductivity cannot be imparted;
This is because if the amount exceeds % by volume, workability and dispersibility will decrease, and there is a possibility that molding of the electromagnetic wave shielding composition will become difficult.

Further, if the number of fibers per unit volume is less than 500 fibers/c11, there is a risk that sufficient conductivity may not be exhibited.

According to a second aspect of the present invention, such a composition contains an oxide of group rVa of the periodic table, NaxAlχ5t(12-
0.1 to 52% of one or more metal compounds selected from the group consisting of silicates represented by χ ) Oz4Nay Sχ, iron group compounds, double oxides with a composite structure of two or more metal oxides, and zinc oxide Part by weight is added.

Although it is not necessarily clear why the addition of one or more of these metal compounds improves the electromagnetic shielding effect, it is possible to suppress the formation of an oxide film on the gold mud fibers by adding the metal compounds mentioned above, and Since the metal compound has semiconductor properties, it has a conductive effect on its own, and the addition of the metal compound improves the rigidity of the resin, which has a combined effect such as preventing separation of metal fibers. Therefore, it can be expected that the electromagnetic wave shielding effect will be improved.

Examples of the above-mentioned oxides of Group IVa of the periodic table include one or more of oxides of titanium (Ti) and zirconium (Zr).

Also, Nax Alx Si<12-X>Oz4N
Examples of silicates represented by ay S z include ultramarine, and examples of iron group compounds include iron (F).
e), cobalt (Co), nickel (Ni), and other compounds. Specific examples of such iron group compounds include (X-Fe304, Sr-Fez
03, PaS z ,, Mn5n-Fez O3,N
iZn-Pe203, Ba-Fe203, Co-F
One or more types such as e03 can be mentioned.

Examples of the double oxide include one or more of rutile type double oxide, spinel type double oxide, reverse spinel type double oxide, and perovskite type double oxide. To give a more specific example, as a rutile type double oxide, for example, Ti02 NiO5b203 (titanium yellow)
, CoOZnO-MgO, etc., and spinel-type double oxides include MgAl20A, Fe
Al104, C0Al204, NagMoOh,
Examples include Na2W 04 and 8gMoo 4. Furthermore, as an inverse spinel type double oxide, Fe”
(Fe”Fe”) Oa, Fe” (TiFe”)
04, Cr(Fe”Cr) Oa, Zn (ZnS
n) Oa, Fe” (Ox /3 Fe”ゝS/3
)04, etc., and peropskite type double oxides include CaTi03, BaTi03, etc.
, Ba5n03, etc. can be cited as examples.

One or more of these gold mud compounds are thermoplastic resins 100%
It is added in an amount of 0.1 to 52 parts by weight based on the weight of the inn.

This is because if the amount of one or more metal compounds added is less than 0.1 part by weight, no improvement in the electromagnetic wave shielding effect can be expected and fluidity will deteriorate.

The particle size of one or more of such metal compounds is preferably 0.
．． 1 to 10 μm, most preferably 0°2 to 5 μm
It is m. If it is smaller than 0.1 μm, it will increase the melt viscosity when added to the resin, so gold rF! 4. It promotes the cutting of fibers, making it difficult to recognize the effect of addition, and
If it is larger than m, even a small amount of addition may cause a decrease in resin strength, resulting in a drawback that impairs practicality.

In the third composition for shielding electromagnetic waves according to the present invention, one or more lubricants selected from the group consisting of fatty acid amides and total soaps are added together with incompletely annealed metal fibers.

Such a lubricant is added so as to be uniformly dispersed in the metal fiber resin by preventing the metal fibers from becoming fiber balls, that is, the gold Eta fibers from curling into a ball shape. Therefore, a molded article manufactured using the electromagnetic wave shielding composition according to the present invention exhibits a stable 'Ei magnetic wave shielding effect, and it becomes possible to manufacture the electromagnetic wave shielding composition with good reproducibility. In addition, by adding this lubricant, it is possible to add a large amount of metal fibers at once, and it also prevents clogging of the extruder nozzle and cutting of the metal fibers, which improves the electromagnetic wave shielding effect. can.

Examples of such fatty acid amides include one or more of ethylene bisstearamide, oxystearamide, stearamide, palmitic acid amide, etc., and metal soaps include:
Cadmium stearate, cadmium laurate, cadmium ricinoleate, cadmium naphthenate, cadmium 2-ethylhexoate, barium stearate, barium laurate, barium ricinoleate, barium naphthenate, barium 2-ethylhexoate, calcium stearate , calcium laurate, calcium ricinoleate, strontium stearate, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, tin stearate. , aluminum stearate, magnesium stearate and the like.

The amount of one or more lubricants selected from the group consisting of fatty acid amides and metal soaps is 0.1 to 2 parts by weight, preferably 0.5 to 1.0 parts by weight, based on 100 parts by weight of the thermoplastic resin.
5 parts by weight is added. This is because if the amount of the lubricant added is less than 0.1 part by weight, there is no effect of adding the lubricant, while if it exceeds 2 parts by weight, there is a risk that the resin molded product will lack mechanical strength.

Further, in the fourth electromagnetic wave shielding composition according to the present invention, one or more of the above-mentioned total bending compounds is added to 100% of the thermoplastic resin.
0.1 to 52 parts by weight are added to the thermoplastic resin, and 0.1 to 2 parts by weight of one or more lubricants are added to 100 parts by weight of the thermoplastic resin.

By adding one or more metal compounds and one or more lubricants in combination in this way, the electromagnetic wave shielding effect can be further improved and an electromagnetic wave shielding composition with good workability can be obtained.

Next, examples of the present invention will be described.

Example 1 To 100 parts by weight of ABS resin, 22% by volume (72 parts by weight) of incompletely annealed fibers with a diameter of 30 μm, a length of 2 mm, and an aspect ratio of 670330°C and ethylene bisstearamide as a lubricant were added. 1.2 parts by weight of was added to measure the electromagnetic wave shielding effect. Measurement was done using Takeda Riken T.
Electric field waves and magnetic field waves were conducted using R-17301 and TR-4172 in combination [electromagnetic wave shielding effect is 100 M for both) average of Iz to 600 MHz].

The results are shown in Figure 1. In the figure, O indicates a magnetic field wave, and Δ indicates an electromagnetic wave shielding effect on electric field waves. For reference, the electromagnetic wave shielding effect of a composition to which the same amount of aluminum fibers that have not been subjected to conventional incomplete annealing treatment is added is shown by (magnetic field wave) and m.

As is clear from FIG. 1, when incomplete annealing was not performed, the electromagnetic wave shielding effect was 20 dB for electric field waves and 10 dB for magnetic field waves when 22% by volume of All1i fiber was added. On the other hand, when the incomplete annealing treatment according to the present invention was performed, a remarkable electromagnetic wave shielding effect of 60 dB of electric field wave and 54 dB of magnetic field wave was obtained. Also, the Izod impact value (per IIIφ) is 7.7 to 9.4 KgcJcm
.

Improved physical properties were also obtained, with a tensile strength of 2.3 to 2.7 Kg/m2, and the electromagnetic wave shielding effect and good physical properties could be satisfied at the same time.

Example 2 To 100 parts by weight of ABS resin, 22% by volume (72% by volume) of At fibers that were incompletely annealed at 330°C with 1.2 parts by weight of ethylene bisstearamide, a diameter of 30 μm, a length of 2 mm, and an aspect ratio of 67. (parts by weight) and titanium oxide as an oxide of the Na group in the periodic table was added in varying amounts, and the electromagnetic wave shielding effect was measured. Is the measurement made by Takeda Riken TI? -17301 and TI? -4172 was used in combination with electric field waves and magnetic field waves [electromagnetic wave shielding effect is 100 MI (average of z ~ 600 M + 1 z] in both cases).

The results are shown in Figure 2. In the figure, ◯ indicates magnetic field waves, and △ indicates electromagnetic wave shielding effect on electric field waves.

As is clear from FIG. 2, by adding titanium oxide, the electric field wave can reach 75 dB or more and the magnetic field wave can reach 64 dl1 or more, which is even better than Example 1. It was found that the effectiveness was significantly improved.

Next, 20℃150%RH-50℃/85%R) l-
20℃150%RH-20℃-20℃150%RH→
The rate of decrease in the electromagnetic shielding effect was measured when a moist heat cycle of 50°C/30% R) I-20°C, 150% RH-20°C was performed for 10 cycles, 2 hours per step and a total of 16 hours.

The results are shown in Figure 3. In Figure 0, ○ indicates that titanium oxide is 100% resin.
This is the electromagnetic wave shielding composition of Example 2 according to the present invention in which 1 part of 17.2fIIff was added to 4 parts of ff, and × indicates the result of the electromagnetic wave shielding composition of Example 1 in which titanium oxide was not added. . The amount of the acid fibers added in both groups was 72 parts by weight, the same as described above.

As is clear from FIG. 3, the electromagnetic wave shielding effect of Example 1 on magnetic field waves ranged from 54 dB to 3 dB after the wet heat cycle.
However, in the electromagnetic wave shielding composition of Example 2 according to the present invention, it decreased to 64 dB (reduced to 70%).
It was found that the rate of decrease was small, 59 dB (92% decrease) from B.

Example 3 To 100 parts by weight of ABS resin, 22% by volume (72 parts by weight) of ^l fibers which had been incompletely annealed at 330°C with a diameter of 30μ steel, a length of 2 mm, and an aspect ratio of 67, and titanium oxide were added. An electromagnetic wave shielding composition was prepared by adding 17.2 parts ffi of ethylene bisstearamide as a lubricant. At this time, the kneading speed of the 41 fiber into the ABS resin required 30 minutes per 1 kg, and the dispersibility was not good (Sample 1).

When 1.2 parts by weight of ethylene bisstearic acid amide was added as a lubricant, it was possible to knead well in 12 to 13 minutes per I kg, so when no lubricant was added, A
It was found that the addition time for one fiber was more than twice as long (Sample 2).

A test piece was produced from such an electromagnetic shielding composition, and the electromagnetic shielding effect was measured. The results are shown in Table 1 below.
and shown as sample 2.

Table 1 Example N 4 The electromagnetic wave shielding composition according to the present invention shown in Table 2 below was manufactured, and the electromagnetic wave shielding effect and the rate of decrease in the magnetic wave shielding effect after a wet heat cycle were measured. 1llJ determination was carried out by the method shown in Example 1 and Example 2.

Table 2 That's not true.

Table 2 ()*ki) Table 2 (continued) shows.

The results of the measurements are summarized in Table 3 below.

Table 3 [Effects of the Invention] As explained above, the electromagnetic wave shielding composition according to the present invention can produce an electromagnetic wave shielding product having a good electromagnetic wave shielding effect, and can also be used in conjunction with a lubricant to improve workability. This method has the advantage that it is also possible to produce an electromagnetic shielding composition with good properties and dispersibility.

[Brief explanation of drawings]

Figure 1 is a graph of the electromagnetic shielding effect of the electromagnetic shielding composition containing Aim fibers that has been incompletely annealed at 330°C according to the present invention. FIG. 3 is a graph showing a measurement of the electromagnetic wave shielding effect of the composition. FIG. 3 is a graph showing the decrease in the electromagnetic wave shielding effect due to moist heat cycling.

Claims (8)

[Claims] (1) An electromagnetic wave shielding composition characterized in that incompletely annealed metal fibers are added to a thermoplastic resin. (2) The electromagnetic wave shielding composition according to claim 1, wherein the metal fiber is annealed at an annealing temperature of 85 to 95% of the complete annealing temperature. (3) In addition to adding incompletely annealed metal fibers to the thermoplastic resin, an oxide of group IVa of the periodic table, NaxAlxSi_(_1_2_
-_x_)0_2_4NaySz 0.1 to 52 1. An electromagnetic wave shielding composition, characterized in that part by weight is added to the electromagnetic wave shielding composition. (4) The electromagnetic wave shielding composition according to claim 3, wherein the metal fiber is annealed at an annealing temperature of 85 to 95% of the complete annealing temperature. (5) Electromagnetic waves characterized by adding incompletely annealed metal fibers to a thermoplastic resin and adding 0.1 to 2 parts by weight of one or more lubricants selected from the group consisting of fatty acid amides and metal soaps. Composition for shielding. (6) The electromagnetic wave shielding composition according to claim 5, wherein the metal fiber is annealed at an annealing temperature of 85 to 95% of the complete annealing temperature. (7) In addition to adding incompletely annealed metal fibers to the thermoplastic resin, an oxide of group IVa of the periodic table, NaxAlxSi_(_1_2_
-_x_)0_2_4NaySz 0.1 to 52 1. An electromagnetic wave shielding composition characterized in that 0.1 to 2 parts by weight of one or more lubricants selected from the group consisting of fatty acid amides and metal soaps are added. (8) The electromagnetic wave shielding composition according to claim 7, wherein the metal fiber is annealed at an annealing temperature of 85 to 95% of the complete annealing temperature.