JPH0361706B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of the Invention] The present invention relates to a conductive resin composition used for shielding electromagnetic waves, and particularly to an electromagnetic wave shielding composition that has a better electromagnetic wave shielding effect than conventional electromagnetic wave shielding compositions. [Background of the Invention] In Western countries, electronic devices such as computers, word processors, etc. It is mandatory to use a housing such as a setter that has been treated to shield electromagnetic waves emitted by the electronic equipment. Electromagnetic wave shielding in electronic equipment as mentioned above is
There is a tendency for this to become mandatory sooner or later in Japan, and various methods of shielding electromagnetic waves are being considered. Shielding of electromagnetic waves as mentioned above can basically be achieved by imparting appropriate conductivity to the housing that encloses the electronic device. Conventionally, zinc was sprayed onto the inner wall of the housing to form a zinc coating. ,
There are well known methods for imparting conductivity to the housing, and methods for imparting conductivity to the housing by applying conductive paint to the inside of the housing. 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, the manufacturing time is reduced because zinc is sprayed or 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, if a housing made by mixing conductive material with thermoplastic resin is intended to maintain a volume resistivity of 10 ^-1 to ^{10 -3} Ωcm, which has an electromagnetic shielding effect, the amount of conductive material mixed must be increased. On the other hand, if a housing with sufficient strength was to be manufactured, the electrical conductivity would not reach the above-mentioned value. 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. [Summary of the invention] The present invention has been made in view of the above points, and
An object of the present invention is to provide an electromagnetic shielding composition that can be used to manufacture electromagnetic shielding products having sufficient strength and conductivity. Therefore, in the electromagnetic wave shielding composition according to the present invention, metal fibers are added to a thermoplastic resin, and a titanium pigment of a multi-component composite oxide having TiO ₂ as a main component is added to 100 parts by weight of the thermoplastic resin. It is characterized by adding 0.1 to 52 parts by weight. Furthermore, the second electromagnetic wave shielding composition according to the present invention includes adding metal fibers to a thermoplastic resin, and adding a titanium pigment of a multi-component composite oxide having TiO ₂ as a main component to 100 parts by weight of the thermoplastic resin. It is characterized in that 0.1 to 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 amides and metal soaps are added. According to the present invention, since an appropriate amount of a composite oxide of a titanium-based pigment containing TiO ₂ is added together with metal fibers, the electromagnetic wave shielding effect can be improved without reducing the strength of the electromagnetic wave shielding molded product. It has the advantage of being able to Further, according to the second composition for shielding electromagnetic waves according to the present invention, an appropriate amount of lubricant is added together with the TiO ₂ titanium-based pigment composite oxide, and an even better electromagnetic wave shielding effect can be achieved. Since the formation of fiber balls in the fibers can be prevented, the metal fibers and the composite oxide of TiO ₂ can be uniformly dispersed, and a large amount of metal fibers can be added at one time.
Therefore, there are advantages in that workability is significantly improved and reproducibility is improved. [Specific Description of the Invention] The present invention will be described in more detail. The electromagnetic wave shielding composition according to the present invention is basically a mixture of metal fibers in a thermoplastic resin, but such a thermoplastic resin is not fundamentally limited, and conventionally Resins used for housings of various types of electronic equipment can be effectively used. For example, polypropylene resin,
It can be one or more of ABS resin, modified PPO resin, polyamide resin, polycarbonate resin, PPS resin, etc. The conductive substance used in the present invention is a metal fiber as described above, but the metal fiber used in the present invention is not fundamentally limited. For example, aluminum fibers, stainless steel fibers, copper fibers, lead fibers, tungsten fibers, molybdenum fibers manufactured by chatter vibration cutting method, pultrusion method, melt spinning method, etc., or Al alloys such as Al-Mg or Al-Ca. One or more types of fibers, copper alloy fibers such as brass, etc. can be effectively used. Furthermore, metal fibers that have been incompletely annealed at an annealing temperature of 85 to 95% of the complete annealing temperature (patent application 1983-
183314) can be used. The amount of metal fibers added to the thermoplastic resin according to the present invention is preferably 5 to 25% by volume, and the number of metal fibers per unit volume is preferably
500 lines/ ^cm3 or more. This is because if the amount of metal fiber added is less than 5% by volume, there is a risk that sufficient conductivity cannot be imparted, and if it exceeds 25% by volume, there is a risk that it will be difficult to mold the electromagnetic wave shielding composition. . In addition, the number of existing pieces per unit volume is 500/
This is because if it is less than cm ³ , sufficient conductivity may not be exhibited. In such a composition, a composite oxide of titanium pigment containing TiO ₂ is added to 100 parts by weight of the thermoplastic resin.
Add 0.1 to 52 parts by weight. Although it is not necessarily clear why the addition of such a complex oxide improves the electromagnetic shielding effect, it is possible that the addition of a complex oxide suppresses the formation of an oxide film on metal fibers. Due to the conductive effect of the composite oxide itself due to its properties as It can be expected that the electromagnetic wave shielding effect will be improved. Titanium-based pigments, which are multi-component composite oxides containing TiO ₂ as the main component, mainly refer to oxides that are a composite of TiO ₂ with a rutile crystal structure and one or more other oxides, and are used as pigments. This is what has been done. Specific examples include TiO ₂ −Cr ₂ O ₃ and TiO ₂ −CoO−, which are well-known as titanium pigments.
NiO−ZnO, _{TiO2 − Sb2O3} − _Cr2O3 , _TiO2 − _NiO
−Sb ₂ O ₃ (titanium yellow), TiO ₂ −BaO−NiO
One or more of the following can be mentioned. Such a composite oxide is added in an amount of 0.1 to 52 parts by weight per 100 parts by weight of the thermoplastic resin. If the amount of the composite oxide added is less than 0.1 part by weight, the effect of adding the composite oxide will not be apparent, while if it is added in excess of 52 parts by weight, no further improvement in the electromagnetic wave shielding effect can be expected, and the fluidity This is because the sex deteriorates. Most preferably it is 0.5 to 15 parts by weight. The particle size of such composite oxide is preferably 0.1
~10 μm, most preferably 0.2-5 μm. If it is smaller than 0.1 μm, it will increase the melt viscosity when added to the resin, promoting cutting of metal fibers, making it difficult to recognize the effect of addition, and
If the diameter is larger than 10 μm, even a small amount of addition may reduce the resin strength, resulting in a drawback that impairs practicality. In the second composition for shielding electromagnetic waves according to the present invention, such composition for shielding electromagnetic waves further includes:
One or more lubricants selected from the group consisting of fatty acid amides and metal soaps are added. Such a lubricant is added so that the metal fibers and composite oxide are uniformly dispersed in the resin by preventing the metal fibers from becoming fiber balls, that is, from curling up into a ball shape. . Therefore, a molded article manufactured using the electromagnetic wave shielding composition according to the present invention exhibits a stable electromagnetic wave shielding effect, and the electromagnetic wave shielding composition can be manufactured with good reproducibility. In addition, by adding this lubricant, it is possible to add a large amount of metal fiber at one time, and it also prevents clogging of the extruder nozzle and cutting of the metal fiber, which improves the electromagnetic wave shielding effect. can. Examples of such fatty acid amides include ethylene bisstearamide, oxystearamide, stearamide, and palmitic acid amide, and examples of metal soaps include cadmium stearate and lauric acid amide. Cadmium acid, cadmium ricinoleate, cadmium naphthenate, cadmium 2-ethylhexoate, barium stearate, barium laurate, barium ricinoleate, barium naphthenate, barium 2-ethylhexoate, calcium stearate, calcium laurate, calcium ricinoleate, stearin Strontium acid, zinc stearate, zinc laurate, zinc ricinoleate, zinc 2-ethylhexoate, lead stearate, dibasic lead stearate, lead naphthenate, tin stearate, aluminum stearate, magnesium stearate, etc. The above can be mentioned. One or more lubricants selected from the group consisting of fatty acid amides and metal soaps are added in an amount of 0.1 to 2 parts by weight, preferably 0.5 to 1.5 parts by weight, per 100 parts by weight of the thermoplastic resin. The amount of lubricant added is 0.1
If the amount is less than 2 parts 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. Next, examples of the present invention will be described. Example 1 100 parts by weight of ABS resin, diameter 30μm, length 2
22% by volume (72 parts by weight) of Al fibers with an aspect ratio of 67 mm and 1.2 parts by weight of ethylene bisstearamide as a lubricant, and yellow as a composite oxide in varying amounts;
The electromagnetic wave shielding effect was measured. The measurement was carried out using Takeda Riken's near-field electromagnetic wave shielding material evaluator (TR-
17301) and spectrum analyzer (TR-4172)
The magnetic field wave (SEH) [shown as the average value of 100MHz to 600MHz] was conducted using The results are shown in Figure 1. The data in which the amount of titanium yellow added is 0 indicates the electromagnetic wave shielding effect of the conventional electromagnetic wave shielding composition. As is clear from Figure 1, when titanium yellow is not added, the electromagnetic wave shielding effect is due to magnetic field waves.
It was 42dB. On the other hand, the electromagnetic wave shielding composition according to the present invention can reach 65 dB or more, and for electric field waves that are relatively easy to shield, values exceeding 75 bB, which is the measurement range of this measuring device, can be obtained. It became clear that the electromagnetic wave shielding effect was significantly improved. Next, 20℃/50%RH→50℃/85%RH→20
℃/50%RH→-20℃→20℃/50%RH→50℃/
The rate of decrease in the electromagnetic shielding effect was measured when a moist heat cycle of 30% RH → 20°C/50% RH → −20°C was performed for 10 cycles, each step having 2 hours and a total of 16 hours. The results are shown in Figure 2. In the figure, ○ indicates the electromagnetic wave shielding composition according to the present invention in which 8.6 parts by weight of titanium yellow is added to 100 parts by weight of resin, and × indicates the results of the conventional electromagnetic wave shielding composition to which titanium yellow is not added. It is. In addition, both compositions
The amount of Al fiber added was the same as above, 72 parts by weight. As is clear from this figure, the electromagnetic wave shielding effect of the conventional electromagnetic wave shielding composition in magnetic field waves decreased from 42 dB to 13 dB (reduced to 31%) after the moist heat cycle, but the electromagnetic wave shielding effect of the electromagnetic wave shielding composition of the present invention decreased from 42 dB to 13 dB (reduced to 31%). It was found that the reduction rate was small, from 65 dB to 58 dB (79% decrease). Example 2 100 parts by weight of ABS resin, diameter 30μm, length 2
In addition to adding 22% by volume (72 parts by weight) of Al fibers with an aspect ratio of 67 mm and an aspect ratio of 67, titanium yellow was added.
An electromagnetic wave shielding composition containing 8.6 parts by weight was produced. The kneading speed of the ABS resin and Al fiber at this time required 25 minutes per 1 kg. When 1.2 parts by weight of ethylene bisstearamide was added as a lubricant as in Example 1, it was possible to knead well in 12 to 13 minutes per 1 kg, so the kneading time could be reduced to about half by adding the lubricant. has become clear. A test piece was manufactured from such an electromagnetic wave shielding composition, and the electromagnetic wave shielding effect was measured. The results are shown in Table 1 below along with Example 1.

〔Effect 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
The combined use of a lubricant has the advantage of making it possible to manufacture electromagnetic shielding compositions with good workability.

[Brief explanation of drawings]

FIG. 1 is a graph showing the electromagnetic shielding effect of the electromagnetic shielding composition according to the present invention, FIG. 2 is a graph showing the decrease in the electromagnetic shielding effect due to moist heat cycles, and FIG. 3 is a graph showing the electromagnetic shielding effect of the electromagnetic shielding composition according to the present invention. A graph showing the electromagnetic wave shielding effect of the electromagnetic wave shielding composition of the example and the decrease in the electromagnetic wave shielding effect due to moist heat cycles. Figure 4 is a graph showing the relationship between the amount of brass fiber filling and the electromagnetic wave shielding effect. Figure 5 is It is a graph when measuring the electromagnetic wave shielding effect of the electromagnetic wave shielding composition of the Example according to this invention.

Claims (1)

[Claims] 1. Adding metal fibers to a thermoplastic resin, and adding 0.1 to 52 parts by weight of a titanium pigment of a multi-component composite oxide having TiO ₂ as a main component per 100 parts by weight of the thermoplastic resin. An electromagnetic wave shielding composition characterized by: 2. Metal fibers are added to a thermoplastic resin, and a titanium pigment of a multi-component composite oxide containing TiO ₂ as a main component is added from 0.1 to 52 parts by weight, a fatty acid amide, and a metal soap to 100 parts by weight of the thermoplastic resin. 1. An electromagnetic wave shielding composition comprising 0.1 to 2 parts by weight of one or more lubricants selected from the group consisting of: