JPH0270404A - Conductive resin composition for molding and electromagnetic shield structure - Google Patents

Abstract

PURPOSE:To manufacture a structure of superior electromagnetic function by coating a conductive fiber composition for giving electromagnetic shield function with thermoplastic resin or a filling material composite plastic resin of given heat deformation temperature range in one direction and using a conductive fiber composite resin composition of two kinds or more of pellet-shaped compositions of given length. CONSTITUTION:A conductive fiber is a metallic fiber or metal coated fiber and constituted at least of two kinds of thermoplastic resin of 80-210 deg.C heat deformation temperature are used. A continuous conductive material line constituted of metallic bundle fibers is manufactured by using said conductive fiber and thermoplastic resin or thermoplastic resin including the filler and setting a crosshead in an extruder and being constituted of said thermoplastic resin is cut into the given length of 3-10mm to manufacture column-shaped pellets. A casing for an electronic instrument can be molded by using said pellets of given length and an ordinary injection molding material.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a columnar pellet in which a conductive fiber bundle is coated in one direction with a thermoplastic a resin having a specific heat distortion temperature range and cut into lengths. The present invention relates to a conductive fiber composite resin composition containing at least two types of t-mix and an electromagnetic shielding structure molded using the same.

[Conventional technology]

For the purpose of shielding electromagnetic waves, various methods have been used to impart a shielding function to plastic molded products, including plating with a metal coating, metal spraying, and conductive coating with a conductive coating. Painting method and metal fabric? 7
A method of molding a resin mixed with a lake-like conductive material is known.

As related to these, Japanese Patent Application Laid-Open No. 59-22710
, JP 59-49918, JP 6 2-4 5
6 5 9 and Japanese Patent Publication No. 62-56069.

[Problem to be solved by the invention]

The above-mentioned conventional techniques are broadly classified into the following two types. One is a method of attaching a conductive film to a plastic molded casing, and the second is a method of molding a resin containing a conductive material to form the casing.

The problems with the former method of attaching a conductive film are that it involves many processing steps and is labor-intensive, and that it requires equipment costs and labor for preparing the working environment.f. In addition, there are concerns regarding reliability, such as the lack of reliability data regarding long-term maintenance of coating adhesion and deterioration of conductive performance, and concerns about changes in shielding function. Can be mentioned.

Regarding the latter molded casing made of sensitive material composite resin, there is a particular problem in that the casting ability is reduced. One problem is that in a repeated thermal shock test (heat cycle test) for evaluating durability performance, conductive performance deteriorates as the number of repetitions increases, resulting in a reduction in shielding effectiveness. Another major problem is that when mixing conductive fibers with resin to make pellets for molding, the fibers are cut due to the shear force when they are mixed with the molten resin, and the shielding effect decreases in proportion to the degree of breakage. The problem is waiting.

Therefore, in anticipation of the cutting of the fiber, it is necessary to fill it in advance for 24 hours.
It is necessary to increase the amount of injection molding, which causes secondary problems such as decreased productivity and increased weight of the original product.

The object of the invention is to solve all the problems of the above-mentioned prior art as well as new problems related to shielding technology. In other words, in order to achieve high productivity and economy, and to maintain the shielding function stably over a long period of time, we developed a new manufacturing method for a conductive fiber composite resin composition suitable for the magnetic wave shielding function and the use of the same. It is an object of the present invention to provide an electromagnetic shielding structure formed by molding. In addition, by newly imparting heat dissipation properties to the conductive resin composition, maintenance of stable operating functions of electronic devices is strengthened.

[Means to solve the problem]

The present invention is a pellet-like composition in which a conductive fiber is coated in one direction with a thermoplastic resin having a specific heat deformation temperature range or a filler composite plastic resin to provide an electromagnetic wave shielding function, and is made into a fixed length. Using two or more types of conductive fiber composite resin compositions, injection molding, transfer molding, pressure m5X, shape,
This is achieved by forming methods such as vacuum/pressure forming and extrusion corrugation, and it is possible to realize a structure with excellent electromagnetic shielding function at a high level in terms of productivity, economy, and reliability.

To improve the electromagnetic shielding performance, the aspect ratio of the conductive fiber should be made thicker (the contact effect of the filled children's picture should be thickened). 2000) ' is an essential component, and by using conductive fibers made of other materials that are not only conductive but also have excellent heat dissipation and economic efficiency, or metal-plated fibers, it is possible to maintain shielding performance and its stability. In addition, it can add industrial value with excellent productivity and economy.

In addition, we have made improvements to the components of the conductive fiber composite resin that have never been seen before.

Conductive fibers are easy to break when mixed with resin using the normal cross-wire method, leading to a decline in shielding performance.Therefore, there is a method to prevent this: conductive fibers are continuously heated in one direction at a specific heat deformation temperature. A novel method for coating with a range of thermoplastics or filled thermoplastics has been developed.

Since the resin coating composition of the conductive fiber is used as a molding material, it is important that it is easy to mold.

Therefore, we set an appropriate length range that maintains formability at a level that does not impede the contact effect.

Furthermore, since the molded product is used as an electromagnetic shielding structure, it is necessary to maintain its shielding function over a long period of time.

In other words, it is necessary to withstand temperature changes in the usage environment and vibration loads during transportation to prevent deterioration of the shielding function strength.

Therefore, in order to achieve this purpose, we devised the use of a thermoplastic resin or filler resin having a specific heat distortion temperature range. By using a resin with a high heat distortion temperature or a filled resin as the base resin, stress relaxation due to thermal stress is reduced (and strength is maintained at a high level and dimensional stability is improved).

Considering the effects of thermoplastic resins and filling resins that have a high heat distortion temperature in a specific range, the former has difficulty relaxing stress due to thermal stress such as so-called cooling/heating cycles, and the conductive resin that exists in the resin It not only prevents misalignment of the contact points between the fibers, but also has the effect of minimizing dimensional changes.

In addition to the above-mentioned effects, the latter filling resin not only reduces the difference in thermal expansion between the conductive fiber and the resin, so it not only has a further effect in preventing displacement of the contact point of the conductive fiber, but also improves heat dissipation. Because of its excellent properties, it can actively dissipate the heat generated when electronic devices are driven, which has a great effect on the stable operation of electronic devices.

[Effect]

The combination of a certain length of conductive wire and a thermoplastic resin or filler material with a specific thermal deformation temperature range, which solves the problem of conventional wires breaking when cross-wired, functions as a long-term electromagnetic wave seal. A significant improvement in the retention effect was achieved.

The use of ultra-fine iron-based metal wire (stainless steel) as an essential component makes it possible to utilize many contact shapes and IEL capabilities, and to increase the ability to conduct injecting by combining it with other conductive injectors. In addition to the improvement effect, when used in combination with copper-based steel, the excellent conductivity of copper can be used to improve conductivity with a small blending ratio. Its low specific gravity had the effect of making the final product's casing lighter.

In addition, by using other conductive fibers such as metal-coated carbon fibers, the specific gravity is originally low.

This produced unprecedented effects in terms of formability and lightweight structure.

In addition, the base resin of the present invention has a high MK type temperature (low stress relaxation), so the degree of change in response to thermal shock tests can be suppressed to a small level, and the electromagnetic shielding performance of the final product housing can be maintained for a long time. It has a sustainable effect.

In addition, the filler increases the dimensional stability of the angle-shaped product and tends to promote heat dissipation, so it has the effect of increasing the operational stability and reliability of electronic equipment.

[Example] The structure of the present invention includes a conductive fiber material, a thermoplastic resin having a specific heat deformation temperature range, or a light-loading resin, and a method for manufacturing a pellet in which these are combined, and a method for manufacturing a pellet using the pellet. and a molded electromagnetic shielding function structure.

These materials, processes, and structures will be described in detail.

The conductive area wire used in the present invention is a metal wire or a metal coated wire. That is, to explain in more detail,
It is made up of at least two types selected from the following groups 1, 3, C'#, and D, and is characterized by consisting of 2 to 5 types of fibers when An is an essential component.

Group 7: Iron-based metal fibers (stainless steel fibers) cross-sectional diameter 5~
15βm Group 3: Copper-based metal fiber (brass, nickel silver) Cross-sectional diameter 15-60z+g Group 0 Nialuminum-based metal fiber (As2S3. Cross-sectional diameter 15-60/Class 1 D group: Metal-coated steel, nickel-plated carbon fiber, Nickel-copper plated glass fiber, nickel-copper plated polymer fiber.

Next, the thermoplastic resin which is the structural modification element of the present invention will be described. A characteristic feature is that a thermoplastic resin having a heat distortion temperature of 80 to 210°C is used. The reason for this is that in order to develop and maintain the electromagnetic wave shielding function of the electronic device housing, which is the ultimate goal, it is necessary to create a so-called network structure by intertwining the conductive fibers three-dimensionally with each other and having contact points. This is because a conductive circuit is formed and the resin needs to have at least a certain level of stress relief in order to maintain the contact pressure of the contacts.

From this point of view, it is desirable that the heat distortion temperature be as high as 210
If it exceeds ℃, the moldability deteriorates, so it is restricted as an upper limit temperature. Therefore, the more preferable heat distortion temperature range is 100~
The temperature is 150°C, particularly preferably 110 to 130°C.

As the thermoplastic resin used in the present invention, any one selected from the following may be used.

These materials can be selected according to the strength level required for the various electronic devices that will ultimately be used.

Thermoplastic resins: polyphenylene ether, polyether sulfone, polybutylene terephthalate.

AES resin, high impact polystyrene, polycarbonate, polyphenylene ether/polystyrene of nylon, polypropylene and polymer alloys, polybutylene terephthalate/polycarbonate, AES resin/polycarbonate, high impact polystyrene/polycarbonate.

The filler is used by blending at least one type selected from the following with the above thermoplastic resin. This is aimed at heat dissipation and dimensional stability.

Group 1: Quartz powder (average particle size 20-50jwm) Group 1: Metal flakes CMy, At) 1-2F + 1ffi angle 10-I
Section 0 group with QQJm thickness: Meriki mica, 1-2 myh square, 10-10
Group 1 of sections with C1xyx thickness: carbon fiber, diameter 7-25 μm, length 1-5 nm
In the above thermoplastic resin, color pigments,
Additives such as flame retardants, internal mold release agents, and antioxidants to α5~5
It is desirable to include wt%.

Using the above-mentioned conductive fibers and a thermoplastic resin with a specific thermal deformation temperature range or a filled thermoplastic resin, a metal bundle fiber is manufactured by setting the crosshead shown in Fig. 1 in an extruder. 5 to 10 coated continuous conductor wires
The cross section of the columnar pellet cut to a certain length of rxm is
As shown in the figure.

In this case, the blending ratio of the conductive material in the thermoplastic resin is determined by the level of shielding ability of unnecessary electromagnetic waves, but it is determined by the regulations of the Federal Communications Commission (FCC) and the voluntary regulations of the Japanese electrical industry. VCCI) etc., and as a result of various studies, the appropriate range of the blending ratio of the conductive resin to the thermoplastic resin excluding the filler is as follows.

Group A: 1 to 10 wt% of iron-based metal wire, Group B: 20 to 5 Qwt of copper-based metal wire, and 2-15 wt% of aluminum-based metal wire, group C: 5 to 15 wt% of metal-coated fiber. One of its characteristics is that fiber is an essential ingredient. Although it is possible to obtain a sufficient shielding effect with iron alone, it has the drawbacks that its conductivity is lower than that of other materials, and its economic efficiency is significantly lower than that of other materials. However, since it has the advantage of being extremely superior in terms of thermal shock %-, it has been found that the disadvantages are small (and that it is optimal to combine it with other materials to make the most of its advantages. Combinations of various types of lead-poured fibers) is selected to meet the required level of the final product, but a total weight fraction of 7 to 40 wtt4 is preferred.

In order to mold a housing for an electronic device using the fixed length of the mold obtained in the present invention, it can be easily molded using an ordinary injection molding material. This is because the volume fraction of the fiber according to the present invention is as small as about 7 uo 1% at most. Although it cannot be said that there is a possibility that the conductive fibers will be cut when injection molding the housing, it is much smaller than the possibility of cutting when the conductive fibers are melted and mixed with the resin when making pellets. O The present invention has a major feature in that it is designed to solve this problem and to obtain pellets of a constant length in order to solve the problem of cutting during melting and cross-wiring.

The present invention will be explained in more detail below using examples.

In describing Examples, typical materials, pellet manufacturing methods, and characteristics evaluation methods will be described.

[Conductive Fiber J Iron-based metal fiber (stainless steel, abbreviated as SUS =
8μm Copper-based metal fiber (abbreviated as Cu): 50μ nickel-plated carbon fiber (abbreviated as Ni-carbon): 12μm Nickel-copper-plated acrylic fiber (abbreviated as Ni-acrylic): 15am [Thermoplastic resin (typical example)] Polycarbonate Resin, heat distortion temperature 150℃ Polyphenylene ether resin, heat distortion temperature 120℃ [filler]
Quartz powder (average particle size 25μm11, 7V-ri (ixlx
o, type 1 section) The method for producing core pellets using the conductive fibers and thermoplastic resin described above uses a twin-screw extrusion method (mixed spacing extrusion screw Diameter 32 cod φ, 3 thread thread, L/D-28
), a conductive fiber bundle was completely continuously supplied, and the single-core continuous body coated with aE with the molten resin was cut to an appropriate length (7-'') after a cooling process.

The single-core pellets obtained here were molded into test pieces (200
M opening x 5 t) and Naruko equipment housing t-i type. The latter case is shown in Figures II, 5, 4 and 5. Note that, if necessary, it is also possible to mix and dilute the base thermoplastic resin, which is usually used for controlling the entire conductive fiber concentration.

Regarding the electromagnetic shielding function of electronic device carcasses.

Shielding ability fir against unnecessary electromagnetic waves generated under the harshest operating conditions of electronic equipment: industry voluntary regulation (VCCI)
)Actually measured according to the contents9.

The thermal shock test was conducted as one of the evaluation measures of the durability of conductive fiber composite resin.The test piece and the electronic device housing were left in a constant temperature bath at 20℃ for 2 hours, and then immediately placed in the next constant temperature bath at 70℃. Thirty cycles were repeated, with one cycle being 2 hours of standing.

Table 1 of Examples shows the volume resistivity of a corrugated test piece used in a columnar pellet of a conductive fiber composite thermoplastic resin manufactured according to the present invention and the radiated electric field strength of an electronic device housing. All values are at a satisfactory level ((). The custom-made values of the conventional method used for comparison are as described in Table 2. Equivalent effects were shown at different blending ratios, which supports the effectiveness of the present invention.Here, regarding the comparative example, the initial characteristic values in Table 2 and the thermal shock test results in Figure 6 will be explained in detail. ..

Figure 2 shows conventional conductive fiber single systems such as copper fiber,
0! 15 pieces with a diameter of 50srm and a length of 7m are produced using an extruder.
Polyphenylene ether resin 50 (comparative example 1) obtained by melt-kneading wt% with resin, copper fiber obtained in the same manner (4
0wt%) Composite Polyphenylene Ether Resin 51 (Comparative Example 2) and Iron-based Metal Fiber L Te5US504, Diameter 8μm, Length 7mm) 1 shows the change in volume resistivity of a flat plate (200a x 50-) injection-molded using No. 1 according to the number of thermal shock test cycles.

When the blending ratio of the conductive fiber is constant (15 wt%), the iron-based metal fiber <5Us504) composite has a smaller volume resistivity and superior electrical conductivity than the copper-based fiber composite. This is thought to be due to the fact that iron-based metal fibers have a smaller diameter and form a much larger number of contacts than copper-based metal fibers, and that copper fibers are more likely to break during kneading.

In order to lower the volume resistivity using copper-based materials, it is necessary to increase the blending ratio, as shown in FIG. 6, 51 and Table 2. X(-1) This is not a good idea as it will increase the specific gravity and decrease the formability and strength of the composite material.

In addition, a molded flat plate of the above composite material was subjected to a thermal shock test (-20'C
The rate of change in volume resistivity after heating (x2A + 70°C x 2L) is much larger for copper-based fibers than for iron-based fibers. Therefore, copper-based fiber composite materials cannot be used practically in terms of durability.

The reason for the large rate of change in volume resistivity of copper-based fiber composites is that their thermal conductivity is large, which promotes stress relaxation in the base resin.
This is thought to be based on the effect of promoting a reduction in the contact pressure at the contact point.

Therefore, it is desirable that the base resin be one that is difficult to relax stress, that is, has a high heat deformation temperature.

Iron-based metal fiber composites have a small rate of change in thermal shock tests, and are very advantageous in this respect, but they require many steps to obtain ultra-fine fibers and are considerably more expensive than copper-based fibers. It is twice as expensive, and it is problematic to use it alone in terms of properties and economy.

From this point of view, we have found that a combined composite metal fiber is effective, taking advantage of the excellent initial conductivity of copper-based metal composite resin, and taking advantage of the small change in thermal shock of iron-based metal fiber. Iron-based fibers have a small wire diameter, so
This takes advantage of the effect of increasing the number of points of contact. Nickel-coated carbon fibers can be used as a substitute for iron-based fibers, but they have some problems in terms of lining construction, volume resistivity, and price, and cannot outperform iron-based fibers. In addition, instead of copper-based metal fiber, aluminum-based metal fiber, nickel-steel plated/polymer fiber, nickel-copper-plated glass fiber can be used, and overall, other metals that have iron-based metal fiber as an essential component can be used. Combination with fiber or metal coated fiber is effective.

Regarding the conductive fiber combination material 72 (Example 5 listed in Table 1) K manufactured according to the present invention, the volume resistivity is also shown in FIG.

Changes in volume resistivity due to thermal shock tests are relatively small.

Note that Example 5 uses a resin with a heat distortion temperature of 120°C for PPE, as in the other Examples, but for reference, when PPE with a heat distortion temperature of 70°C is used (as shown in 71). ), the rate of change in volume resistivity becomes significantly large.

This is due to the large effect of promoting stress relaxation.

Next, the examples in Table 1 and l! Table 3 and FIG. 7 show the results of a thermal shock test for representative examples of conductive fiber compositions shown in Comparative Examples in Table 2. Part of the volume resistivity is also shown in FIG.

As shown in Table 5, in Comparative Example 1 and Comparative Example 2 according to the prior art, the change in volume resistivity was suddenly large, and the magnetic wave shielding function after 60 thermal shock tests of the electronic device housing was decreases significantly to the point where it cannot be put to practical use at all.

Initial value of Example 1 (indicated by 73) and thermal shock test 30
As shown in FIG. 7, it can be seen that the radiation electric field strength of the electronic device housing after rotation (indicated by 73') is extremely stable and excellent. Example 5 is also at an excellent level.

Book 1: Quartz powder: 2Qwt% light-loaded PPE, *2: At7: 1Qwt% light-loaded pc unnecessary electromagnetic waves ta
It embodies the most effective method of providing a shielding function, and its unique effects will be described in terms of elemental technology.

In the method of manufacturing conductive fiber composite pellets, single-core wire pellets of a certain length are obtained without any fiber cutting, and in addition to fully exhibiting the conductive function, the contact effect is achieved by using iron-based ultrafine fibers as an essential component. It is possible to improve the conductivity, that is, the shielding function, with a small blending ratio when used in combination with other conductive fibers, and therefore has good formability (and suppresses the increase in specific gravity). In addition, the use of fillers maintains the dimensional stability of the molded product as a whole and improves heat dissipation, which has the effect of improving the operational stability of electronic devices.Also, the molded product has a high heat distortion temperature. The base resin greatly improves thermal shock resistance.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing a crosshead for manufacturing a single core wire used in the present invention, Fig. 2 is a perspective view showing a pellet cut to a certain length, and Fig. 3 is a cross-head for manufacturing a single-core wire used in the present invention. C
RT unit, Fig. 4 is a sectional view taken along line A-A in Fig. 3, Fig. 5
The figure is an exploded perspective view of a CRT unit, FIG. 6 is a relationship diagram between volume resistivity and thermal shock cycle, and FIG. 7 is a characteristic diagram showing frequency characteristics of radiated electric field strength of electronic equipment. 1... Conductive fiber introduction hole, 6... Filler filled thermoplastic resin. //---E) Mulinis/3-...cy;7UniV) 20th Akira 7 7θ /θθ Intermediate teaching, (, MHx) 3117θ

Claims (1)

[Scope of Claims] 1. Iron-based metal fibers are an essential component, and at least one kind of conductive fibers of different materials and diameters are formed into independent bundles, continuously in length and direction, and subjected to specific thermal deformation. A molding resin composition having electrical conductivity and consisting of a mixed system of columnar pellets of a certain length coated with a thermoplastic resin filler composite thermoplastic resin having a temperature range. 2. Continuously feed a bundle of ferrous metal fibers as conductive fibers to the crosshead of the extruder, and use thermoplastic resin or filler composite thermoplastic resin in a specific heat deformation temperature range that is plasticized and melted in the main body. After coating and cooling process, 6-1
Using a monocore columnar pellet cut into lengths of 0 mm as an essential component, and a bundle of conductive fibers of different materials and diameters, the same method was used to continuously identify the properties in the length direction. coated with thermoplastic resin with a heat deformation temperature range of 3 to 9 m.
An electrically conductive molding resin composition composed of at least one selected from columnar pellets cut into a certain length within a range of m. 3. As a conductive fiber, iron-based metal fiber is an essential component, and at least one conductive fiber of different material and diameter.
A multi-core product in which seeds are arranged in parallel as bundle-shaped independent cores, simultaneously coated continuously in the length direction with filler composite thermoplastic resin, and cut into constant lengths within the range of 6 to 10 mm. A conductive molding resin composition in the form of columnar pellets. 4. Iron-based metal fibers have an aspect ratio of 400 to 200.
0 and a diameter of 5 to 15 μm, and conductive fibers of different materials and diameters include copper-based metal fibers, aluminum-based metal fibers, and metal film-coated fibers with an aspect ratio of 50 to 600 and a diameter of 15 to 60 μm. 6. The conductive molding resin composition according to claim 1, wherein the resin composition is selected from at least one of inorganic fibers and metal film-coated organic fibers. 5. The conductive molding resin composition according to claim 4, wherein the blending ratio of the conductive fiber to the thermoplastic resin is as follows. Iron-based metal fiber: 1-10 wt% Copper-based metal fiber: 20-30 wt% Aluminum-based metal fiber: 2-15 wt% Metal film-coated inorganic fiber: 5-15 wt% Metal film-coated organic fiber: 5-15 wt% 6. Iron The copper-based metal fiber is at least one of copper, brass, or nickel silver fiber, the aluminum-based metal fiber is aluminum fiber, and the metal film-coated inorganic fiber is 5. The conductive conductive material according to claim 4, wherein the at least one kind of nickel-plated carbon fiber or copper/nickel-plated glass fiber is used, and the metal film-coated organic fiber is at least one kind of steel or nickel-plated organic polymer fiber. Resin composition for molding. 7. The conductive resin composition according to claim 1, 2 or 3, wherein the thermoplastic resin has a heat deformation temperature range of 80 to 210°C. 8. A where the thermoplastic resin is ABS resin, high impact polystyrene, polycarbonate, polyphenylene ether, polyether sulfone, polybutylene terephthalate, nylon, polypropylene and polymer alloys.
BS resin/polycarbonate, impact-resistant polystyrene/
Claim 1, characterized in that it is one of polycarbonate, polyphenylene ether/polycarbonate, and polybutylene terephthalate/polycarbonate.
6. The conductive resin composition according to 2 or 5. 9 For thermoplastic resin, filler is 5% for thermoplastic resin.
Claim 1, characterized in that it contains ~20% by weight,
3. The conductive resin composition according to 2 or 3. 10. The filler is quartz powder with an average particle size of 20 to 30 μm, 2 m
The conductive resin composition according to claim 9, characterized in that the conductive resin composition is at least one of metal flakes of m square or less, plated mica pieces of 2 mm or less square, and carbon fibers of 7 to 25 μm in diameter and 2 to 5 mm in length. thing. 11. An electromagnetic shielding structure molded using the conductive resin composition according to claim 1, 2 or 3. 12. The electromagnetic shielding structure according to claim 11, wherein the electromagnetic shielding structure is an electronic device housing or an antistatic electronic component container, and is molded by injection molding, transfer molding, or vacuum/pressure molding. 13. The electromagnetic shielding structure according to claim 11, wherein the electromagnetic shielding structure is an electromagnetic shielding wall, an electronic blackboard protection branch, and a sign protection branch, and is formed by extrusion sheet molding.