JP4355870B2 - Highly flame retardant electromagnetic shielding gasket and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic wave shielding gasket that achieves both high flame retardancy and electrical conductivity, and a method for producing the same.
[0002]
[Prior art]
2. Description of the Related Art Electronic devices such as computers and word processors, and other various electronic devices incorporating a microcomputer as a control element are likely to malfunction due to disturbances such as electromagnetic waves entering the device from the outside. In addition, these electronic devices often generate harmful electromagnetic sources by generating electromagnetic waves outside the device casing during operation. In order to protect the electronic device from interference of this kind of electromagnetic waves (EMI) and interference from lower frequency radio waves (RFI), and to prevent leakage to the outside, a shield (shield) is provided in the device housing. Generally applied to the body.
[0003]
This electromagnetic wave shielding is performed, for example, by applying a conductive paint to the inside of the housing that forms the casing of the computer, or covering the central processing unit (CPU) with a metal plate or a metal mesh. By the way, since the case of the computer generally has a divided structure of a plurality of parts, it is not suitable for a slight gap generated when these covers are fitted, or for an installation location such as a connector terminal for connecting various modules. It is known that electromagnetic waves intrude or leak from gaps that occur in an evasive manner, causing the device to malfunction as well. For this reason, by adhering a soft conductive member in the form of a sheet, for example, to a location along the parting line of the housing or an installation site such as a connector terminal, electromagnetic waves can enter the housing or externally. Technology is being implemented to prevent leakage. Since this conductive member fills a division gap or the like when a plurality of parts are combined by the casing, it is generally called a gasket, paying attention to its function. Therefore, this term will be used hereinafter in the specification of the present application.
[0004]
As this type of technology, a foamed material having elasticity such as polyurethane foam is formed into a core material to form a core material, and the core material is covered with a woven fabric of conductive fibers, or a conductive fabric. A gasket (US Pat. No. 4,857,668) is known in which wet or dry metal plating is applied to a material and the periphery of the core material is covered with a conductive cloth material. Japanese Patent Laid-Open No. 2-296396 discloses an electromagnetic wave shielding gasket in which an elastomer core is surrounded by a conductive wire mesh instead of using conductive fibers or conductive cloth.
[0005]
The electromagnetic shielding gasket described above is extremely effective in that it can prevent electromagnetic intrusion and external leakage by being provided along the dividing line of the housing or provided in the mounting opening of a connector terminal or the like. However, the conductive fibers, conductive cloths and other conductive wire meshes that make up part of these gaskets are not flexible in material, and are considerably more rigid than polyurethane foam, which is the core material. It has become. For this reason, there is no problem if the dividing line in the case (conducting treatment by applying conductive paint, resin molding of conductive powder, etc.) is straight, but the dividing line has small irregularities depending on the location. If they are formed or curved with a relatively small curvature, the conductive fibers and wire mesh are difficult to follow due to their rigidity when the gasket is disposed, and wrinkles are difficult. As a result, the gap cannot be completely filled, and there is a serious difficulty in allowing the electromagnetic wave to enter from outside.
[0006]
[Problems to be solved by the invention]
  In order to avoid such problems, the core material and the core material are coated.LeadIt is proposed to use a flexible elastic body such as urethane for both of the electrically conductive coating layers. However, since these elastic bodies are generally high molecular organic substances and easily burnt, there is a problem of ignition or melting when they are incorporated in an electronic device casing such as a computer or a word processor that generates a lot of heat. In particular, regarding these electronic devices, the United States has a high flame retardant property in the UL standard, so it is absolutely necessary to clear the standard for export to the United States, and a higher standard. It is desirable to receive certification at the standard. Therefore, as a method of increasing the flame retardancy in the gasket, a method of putting a large amount of flame retardant into the raw material of the elastic body can be considered, but in this case, the hardness of the elastic body becomes high and the shape followability is inferior. Is pointed out. That is, it has been very difficult to produce an elastic body for electromagnetic wave shielding that has both flexibility and high flame retardancy.
[0007]
OBJECT OF THE INVENTION
SUMMARY OF THE INVENTION The present invention has been proposed in view of the problems associated with the prior art, and has been proposed to solve this problem. The gasket for electromagnetic wave shielding has high flame retardancy and also has flexibility, and a method for producing the same. The purpose is to provide.
[0008]
[Means for Solving the Problems]
  In order to overcome the above-mentioned problems and achieve the intended purpose, the highly flame-retardant electromagnetic shielding gasket of the present invention comprises a core material made of a porous elastic body obtained by foaming melamine resin,
  It is composed of a flame-retardant and flexible conductive coating layer that covers the outer surface of the core material.,
  The conductive coating layer is composed of a catalytic metal layer having catalytic activity for a predetermined plating metal and a metal plating layer applied to the surface of the catalytic metal layer, through a resin layer containing a flame retardant. Bonded to the coreIt is characterized by that.
[0009]
In order to overcome the above-mentioned problems and achieve the intended purpose, another method of manufacturing a highly flame-retardant electromagnetic shielding gasket according to the present invention is to produce a core material of a porous elastic body by foaming melamine resin. ,
Forming a resin layer of a moisture curable resin containing a flame retardant on the outer surface of the core material;
This resin layer is provided with a catalytic metal layer having catalytic activity for the required plating metal,
Next, the plating metal is deposited on the catalytic metal layer to form a metal plating layer.
[0010]
In order to overcome the above-mentioned problems and achieve the intended purpose, another method of manufacturing a highly flame-retardant electromagnetic shielding gasket according to the present invention is to provide a porous elastic core material by foaming melamine resin. Made,
Forming a resin layer of a synthetic resin capable of being plated containing a flame retardant on the outer surface of the core material;
After a predetermined roughening treatment on the outer surface of the resin layer, a catalytic metal layer having catalytic activity is applied to the required plating metal,
Next, the plating metal is deposited on the catalytic metal layer to form a metal plating layer.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, a highly flame-retardant gasket for electromagnetic wave shielding and a method for producing the same according to the present invention will be described below with reference to the accompanying drawings.
[0012]
As shown in FIG. 1, an electromagnetic wave shielding gasket according to a preferred embodiment of the present invention includes a core material 10 made of a porous elastic body of melamine resin, and a conductive coating that covers the entire core material 10 or a required portion. It is basically composed of the layer 12. The conductive coating layer 12 includes: (1) a resin layer 14 formed from a resin 20 and having a characteristic of adsorbing a catalyst metal 22 described later; and (2) a catalyst metal layer 16 adsorbed on the resin layer 14. And (3) a metal plating layer 18 formed with fine particles of the catalyst metal 22 forming the catalyst metal layer 16 as nuclei.
[0013]
As the core material 10, a porous elastic body (hereinafter referred to as “melamine elastic body”) obtained by foaming a melamine resin having extremely high flame retardancy as a raw material is used. The melamine elastic body is prepared by adding a foaming aid and a catalyst to a melamine resin aqueous solution or water dispersion and heating, and has an extremely fine cell diameter (about 10 to 50 μm) and a high porosity (density 5 to 20 kg / m^ThreeA continuous breathable non-combustible porous body. The core material 10 is used by being formed into a sheet shape or a string shape according to the structure inside the electronic device casing to be arranged. In the case of a sheet shape, a thickness of about 20 to 1 mm is preferable, and in the case of a string shape, a width of about 20 to 2 mm is preferable.
[0014]
The resin 20 forming the resin layer 14 is roughly classified into the following two types.
1: Synthetic resin that can be plated by conventional plastic plating method
Examples of the resin 20 that can be used in the present invention include a synthetic resin capable of plastic plating. Examples of such resins include ABS (acrylonitrile butadiene styrene resin), PC (polycarbonate resin), PC / ABS (alloy of PC and ABS), PA (polyamide resin), PPS (polyphenylene sulfide resin), PES (polyethylene resin). Ether sulfone resin), PEI (polyetherimide resin), PPO (modified polyphenylene oxide resin), POM (polyoxymethylene resin), PP (polypropylene resin), PBT (polybutylene terephthalate resin) and the like. A flame retardant mixed with a predetermined amount of flame retardant is used. In addition, since the pre-processing method including the mechanical or chemical roughening process according to each material is established in the resin layer 14 formed from this synthetic resin which can be plated, this process is given beforehand. Thus, the catalyst metal 22 can be applied.
2: Moisture curable resin
A typical example is a moisture curable modified silicone resin. This is a resin having a certain degree of flame retardancy and a characteristic of being cured by atmospheric moisture. In order to develop the high flame retardancy comparable to that of the melamine resin, a flame retardant is added and suitably employed. A thickness of about 0.05 to 0.5 mm is used to form an impermeable continuous layer that completely blocks invasion of various chemicals for electroless plating or electrolytic plating on the core material of the melamine elastic body. Desired. The moisture-curing modified silicone resin generally has a high viscosity and can be applied by a roll coater or the like, and the concentration can be adjusted with a solvent such as xylene, so that a uniform and thin resin layer 14 can be easily formed. . Moreover, since it hardens | cures with atmospheric humidity, a cure rate can also be easily controlled by controlling the moisture at the time of providing to the core material 10. FIG. The modified silicone resin has a high physical adhesion ability to various substances and has a large number of functional groups newly generated by reaction with functional groups remaining in the structure in an unreacted state after curing or with moisture. However, it is presumed that a strong adhesion to the metal plating layer 18 is indirectly developed by capturing and adsorbing a large number of the catalyst metals 22.
[0015]
As the flame retardant mixed with each of the resins 20 described above, a known flame retardant may be adopted. However, from the viewpoint of environmental protection, it is difficult to contain a halogen compound and to be mixed in a small amount. Those exhibiting flammability are suitably employed. Also, it should be considered that the flame retardant mixed in the resin 20 does not bleed on the surface of the resin 20 and does not affect the electronic component. As what satisfy | fills these various conditions, a red phosphorus flame retardant is mentioned, for example. As other flame retardants, it is desirable to use a hydrated metal compound or a nitrogen compound in combination. In this case, the flammability is suppressed and the shielding effect from oxygen is improved, so that the flame retardancy is further improved.
[0016]
As the catalytic metal 22, a noble metal having catalytic activity for electroless plating reaction such as palladium is preferably used, and gold, silver, ruthenium, rhodium, palladium, iridium, osmium, or platinum can be used. The method of forming the catalyst metal layer 16 by applying the catalyst metal 22 to the resin layer 14 differs depending on whether a synthetic resin that can be plated by a conventional plastic plating method or a moisture curable resin is used. A specific method will be described later. The catalytic metal layer 16 does not need to be formed as a continuous layer, and may be adsorbed on the resin layer 14.
[0017]
The plating metal 24 includes a first plating metal 24a for forming the first metal plating layer 18a and a second plating metal 24b for forming the second metal plating layer 18b, which are high with respect to incident electromagnetic waves. A metal having reflectivity, that is, a metal having high conductivity and a metal having high corrosion resistance is employed. In general, copper, nickel / phosphorus alloy, nickel / boron alloy, silver, gold, palladium, tin, solder, cobalt or the like can be used. In particular, the first plating metal 24a is gold, silver or copper. However, as the second plating metal 24b, nickel-phosphorus, nickel-boron, gold, palladium, chromium, or the like is preferable.
[0018]
【Production method】
The manufacturing method of the highly flame-retardant electromagnetic shielding gasket according to the present invention is largely divided into a pretreatment step S1, a conducting step S2, and a finishing step S3 as shown in FIG. The pretreatment step S1 includes a core material production stage S11 for producing a melamine elastic body to be the core material 10 and processing it into a predetermined shape, and a resin indispensable for performing metal plating on the core material 10 which is an electrical non-conductor. It consists of resin layer application | coating step S12 which forms the layer 14. FIG.
[0019]
The conducting step S2 performed subsequent to the pretreatment step S1 is: (1) a catalyst containing desired catalytic metal fine particles that express catalytic activity against electroless plating in the resin layer 14 formed on the core material 10; A catalyst adsorption step S21 in which the metal 22 is adsorbed to form the catalyst metal layer 16, and (2) a predetermined thickness on the catalyst metal layer 16 by being immersed in a first plating bath 30 that is appropriately and selectively employed. A first plating step S22 for applying the first metal plating layer 18a, and (3) a second metal plating layer 18b for applying the second metal plating layer 18b on the first metal plating layer 18a by being immersed in the second plating bath 32. It consists of plating step S23. After passing through the above steps, the processing and inspection in the inspection step S3 are performed to complete the application of metal plating to the electrical non-conductor. In some cases, subsequent to the first plating step S22 and the second plating step S23, an electrolytic plating step S24 may be performed to make the metal plating layer 18 thicker. This electrolytic plating step S24 is appropriately and selectively performed according to various physical properties (for example, conductivity) required for the gasket.
[0020]
In the core material production step S11, as described above, the melamine elastic body is produced from the melamine resin raw material, and the production method is as follows. ： Melamine / formaldehyde initial condensate, water, anionic surfactant as foaming agent, acid (catalyst) and foaming aid (low boiling point liquid not mixed with water) are mixed in predetermined amounts and stirred at high speed. After that, it is rapidly foamed and cured by irradiating microwaves promptly. After the production, secondary curing is performed in order to remove free formalin and residual water. Even in combination with the melamine / formaldehyde initial condensate, a highly flame retardant foam is used even when a copolymer using an amino resin raw material such as urea / formaldehyde initial condensate or an initial condensate of guanamine compound and formaldehyde is used. It is possible to obtain an elastic body.
[0021]
Since the resin application step S12 and the catalyst adsorption step S21 differ in the following manufacturing processes due to the difference in the resin applied in the resin application step S12 (resin that can be plated by the conventional plastic plating method or moisture curable resin). Each will be described individually.
[0022]
1: When the resin layer 14 is formed from a synthetic resin that can be plated by a conventional plastic plating method
Resin application step S12: The surface of the core material 10 is thinly coated with a synthetic resin that can be plated. For this coating, the resin is dissolved and applied by means of spraying or brushing, etc., and the resin is applied to the surface of the core material 10 while being extruded into a film or tube in a molten state by an extruder. The so-called extrusion coating method can be used. In the case of the coating method, attention is paid to the porous property of the core material 10 and the viscosity is adjusted to be high so that the resin layer 14 is formed only near the surface.
Catalyst adsorption step S21: First, washing with an alkaline aqueous solution is carried out in order to remove oily grease and the like during molding of the surface of the core material 10. This alkaline aqueous solution usually contains sodium phosphate or a nonionic surfactant that facilitates catalyst adsorption. Next, a chemical roughening method corresponding to the type of the resin is applied. For example, in the case of an ABS resin, a fine concavo-convex structure is formed on the surface and roughened by immersing it in a high-concentration solution of chromic anhydride and sulfuric acid at a high temperature to dissolve the butadiene rubber phase. This is done by adding a group. In the case of PC, prior to the etching with the chromic acid / sulfuric acid mixed solution, a method of immersing in an organic solvent to swell the resin surface and roughening by crack formation due to the generation of stress is suitably employed. For PA, a filler is contained and etching with concentrated hydrochloric acid is generally used. When the etching is completed, complex colloid consisting of tin and palladium chloride is finally adsorbed on the roughened surface, and then immersed in an accelerator bath containing sulfuric acid to adsorb only palladium metal nuclei on the surface. Thus, the catalytic metal layer 16 is formed.
[0023]
2: When forming the resin layer 14 from moisture curable resin
Resin provision step S12: A red phosphorus flame retardant, a hydrated metal compound, a nitrogen-containing compound, or the like is blended and kneaded with the moisture curable resin. The compounding ratio in this case is 5 to 20 parts of red phosphorus flame retardant with respect to 100 parts by weight of the curable resin resin. However, depending on the required degree and content of flame retardancy, the hydrated metal compound or nitrogen-containing compound May be added up to about 100 parts or 25 parts, respectively. Since the blend produced in this way has a high viscosity, it is preferable to use a roll coater or the like for application to the core material 10, and it is rapidly cured by moisture in the air at room temperature or under heating.
Catalyst adsorption step S21: A colloid of catalytic metal 22 having catalytic properties for electroless reaction is applied and adsorbed on the surface of the resin layer 14 by a method such as dipping, spray coating or brush coating. The colloid of the catalytic metal 22 can be obtained by dissolving a water-soluble salt of the catalytic metal compound, adding a surfactant and adding a reducing agent while stirring vigorously. There are various types of surfactants, and anionic or cationic surfactants are preferable, such as soap, sodium higher alcohol sulfate, sodium alkylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, and lauryl. Trimethylammonium chloride or alkylbenzyldimethylammonium chloride is used.
[0024]
In the plating steps S22 and S23 in the conductive step S2, the first plating metal 24a having conductivity and the second plating metal 24b having corrosion resistance are applied on the catalytic metal layer 16 by electroless or electrolytic plating. To do. The plating employed in the first plating step S22 and the second plating step S23 is preferably electroless plating that does not require power supply in any case. Specifically, the management of the plating bath is relatively easy and industrial. Therefore, electroless copper is used for the first metal plating layer 18a, and electroless nickel-phosphorous alloy is used for the second metal plating layer 18b. In addition, the thicknesses of the first plating layer 18a and the second plating layer 18b at this time are preferably about 0.2 to 2 μm and 0.1 to 1 μm, respectively. This is because if it is too thick, the production time and production cost increase, and if it is too thin, the desired function cannot be achieved.
[0025]
In the first plating step S22, a first plating metal 24a ion stabilized by a chelating agent or the like and a reducing agent capable of reducing the ion coexist at an appropriate pH and temperature. This is performed by immersing the core material 10 on which the catalytic metal layer 16 is adsorbed in the plating bath 30. The first metal plating layer 18a is formed by a precipitation reaction using the catalyst metal 22 adsorbed in the previous step S21 as a nucleus. The subsequent second plating step S23 is performed by using the second plating bath 32 in which ions of the second plating metal 24b are stabilized by a chelating agent or the like, and the pH and temperature conditions are appropriate. As described above, the first plating layer 18a formed from the first plating metal 24a mainly exhibits a shielding property for reflecting incident electromagnetic waves with high conductivity, and the first plating layer 24a is formed from the second plating metal 24b. The second plating layer 18b formed in a stacked manner on the one plating layer 18a exhibits high corrosion resistance and protects the first plating layer 18a.
[0026]
The metal plating layer 18 composed of the first metal plating layer 18a and the second metal plating layer 18b can improve the electromagnetic wave shielding ability in proportion to the thickness thereof. However, since the physical properties that cause large compressive deformation with low stress are essential for the gasket, the first metal plating layer 18a and the second metal plating layer 18b are the minimum that can ensure predetermined shield (conductivity) and corrosion resistance, respectively. The thickness is preferred.
[0027]
By the pretreatment step S1 and the conductive step S2 performed so far, the gasket 28 on which the conductive coating layer 12 having a desired electromagnetic wave shielding property is formed can be obtained from the core material 10. In the final finishing step S3, the gasket 28 is subjected to molding and inspection such as washing and drying, cutting into a predetermined shape or punching.
[0028]
Although the preferable experimental example of this invention is shown below, it is not limited to these Examples.
[0029]
[Example 1]
▲ 1 ▼ Core production stage
A raw material of the following formulation was weighed into a cup, and stirred for 45 seconds with a stirrer set at a rotational speed of 3000 rpm. After stirring, 330 g was put into a prepared PP test piece mold having an inner size of 400 × 400 × 70 mm, the piece mold was clamped, and the microwave was irradiated with a microwave generator with an output of 1 kW for 140 seconds. After irradiation, the foam was removed from the piece mold, and put into a curing furnace set at 150 ° C. for 4 hours to dry and cure to obtain a melamine elastic body.
(Combination prescription)
100 parts by weight of trimethylolmelamine
Water 35
Sodium dodecylbenzenesulfonate 20
Formic acid 2
Pentane 20
[0030]
The cured foam is cut with a Tachi machine (cutting machine) to cut the skin layer of the melamine elastic body to a thickness of 10 mm, and further cut to a width of 10 mm to form a 10 × 10 × 400 mm string core A material was used. The mechanical properties of this core material were as follows.
Foam density [kg / m^Three] 8
Tensile strength [Mpa] 0.018
Elongation [%] 20
Tearing strength [N / cm] 0.45
50% compression set [%] 26.8
Repeated compression strain [%] 7.0
(Test method conforms to JIS K 6401)
[0031]
(2) Resin application stage
Moisture curable modified silicone resin (product name Super X: manufactured by Cemedine) 100 parts by weight of red phosphorus flame retardant (product name Nova Excel F5: manufactured by Rin Chemical Industry Co., Ltd .: average particle size 6 μm, phosphorus content 93% ) Was added and mixed in a dry nitrogen with a twin-screw kneader to obtain a heat-resistant moisture-curable resin. Next, the core materials were arranged, and the resin was applied to a thickness of about 0.1 mm by a bar coater one by one, and dried in air for 1 hour. This coating operation was performed a total of four times, and the entire periphery was covered with a resin layer formed from a flame retardant resin.
[0032]
(3) Catalyst adsorption stage
Palladium chloride (PdCl₂) To a main solution obtained by adding 0.1 g / L of stearyltrimethylammonium chloride (product name: Cotamine 86P Conch) to a pure aqueous solution of 0.089 g / L and 0.146 g / L of sodium chloride (NaCl), 0.076 g sodium borohydride (NaBH) in a small amount of pure water_FourThe solution was dissolved vigorously while adding a solution in which a black-brown transparent palladium colloid catalyst solution was prepared. This palladium colloid catalyst solution was sufficiently applied by spray coating to the core material produced in the pretreatment step, and then dried at a temperature of 100 ° C. for 30 minutes in a high-temperature oven capable of setting the temperature.
[0033]
(4) First plating stage
After washing with water, an electroless copper plating bath (product name Omnishield 1598: Shipley Far East Co., Ltd .: standard composition) is plated for 30 minutes at a temperature of 30 ° C. to form a first metal plating layer of about 1 μm. Formed.
(5) Second plating stage
Then, an activation bath containing palladium chloride (Omnishield 1501: manufactured by Shipley Far East Co., Ltd .: standard formulation) was treated for 1 minute at a temperature of 25 ° C. to obtain surface activity. After sufficiently removing the activation bath solution by washing with water, an electroless nickel plating bath (product name: Omnishield 1580: manufactured by Shipley Far East Co., Ltd .: standard composition) is used as the second plating stage under the condition of a temperature of 30 ° C. Plating was performed for 5 minutes to form a second metal plating layer of about 0.25 μm.
(6) Finishing process
Washing and drying were sufficiently performed to obtain a gasket.
[0034]
(result):
When the resistance between the opposing sides was measured while compressing the gasket thus obtained by cutting it to a length of 50 mm, the conductivity was good at a resistance value of 0.05Ω or less between 10% and 80% compression rate. Results were obtained. Further, when a combustion test was performed according to the UL94 flame retardant evaluation criteria, the flame did not ignite at all, or the flame disappeared immediately after ignition, and the evaluation was rating = V0. From these results, it is determined that the gasket obtained in this experimental example has both sufficient EMI shielding properties and flame retardancy.
[0035]
[Example 2]
A melamine elastic body was obtained through the same formulation as in the first experimental example and (1) the core production stage. The cured foam was cut with a Tachi machine (cutting machine) from the skin layer of the melamine elastic body and sliced to a thickness of 3 mm to obtain a sheet-like core material of 400 × 400 × 3 mm. The mechanical properties of the core material are the same as those in the first experimental example, and will not be described.
[0036]
(2) Resin application stage
Moisture curable modified silicone resin (product name Super X: manufactured by Cemedine) 100 parts by weight of red phosphorus flame retardant (product name Nova Excel F5: manufactured by Rin Chemical Industry Co., Ltd .: average particle size 6 μm, phosphorus content 93% ) 10 parts and 50 parts of aluminum hydroxide (product name: Heidilite H42M: Showa Denko Co., Ltd .: average particle size: 1.0 μm) are added and mixed in a dry-screwed biaxial kneader in a flame retardant moisture curable A resin was obtained. Next, the core materials were arranged, and the resin was applied to a thickness of about 0.1 mm by a bar coater one by one and dried in air for 1 hour. This coating operation was performed on both surfaces of the sheet-like core material. Next, (3) catalyst adsorption step, (4) first plating step, (5) second plating step, and (6) finishing steps similar to those in the first experimental example 1 were sequentially performed to obtain a finished product.
[0037]
(result):
Using the completed gasket thus obtained, the shielding effect of the electric field wave and the magnetic field wave was measured according to the KEC method for the EMI shielding effect. The electric field wave was 70 dB or more and the magnetic field wave was 40 dB or more under the condition of the frequency between 100 MHz and 1000 MHz. Moreover, when a combustion test was conducted according to UL94 flame retardancy evaluation criteria, it was V0 evaluation.
[0038]
[Example 3]
▲ 1 ▼ Core production stage
A string-like core material having a size of 10 × 10 × 400 mm was obtained through the same blending prescription as in the first experimental example and {circle around (1)} core material production stage and processing. The mechanical properties of the core material are the same as those in the first experimental example, and will not be described.
[0039]
(2) Resin application stage
Using a crosshead having an opening with an outer peripheral dimension of 12 × 12 × 0.1 mm and a hollow part through which the core material to be coated passes, a flame-retardant ABS resin (Psycolac) melted from the outer periphery of the opening VW22: manufactured by Ube Saikon Co., Ltd .: Flame Retardant UL94-V0), and from the hollow portion of the die, each of the string-like core materials is extruded or sent out to form an ABS resin resin layer on the surface of the core material. Formed.
[0040]
(3) Catalyst adsorption stage
First, processing was performed so that the core material was not exposed on the end face, and the position was fixed by hanging on the rack. Next, the core material is a cleaning solution containing an aqueous solution of sodium hydroxide (25 g / L), sodium carbonate (25 g / L) and sodium phosphate (25 g / L) and a nonionic surfactant (1 g / L). The inside was degreased. Subsequently, an etching solution obtained by mixing an aqueous chromic anhydride solution (420 g / L) and 98% sulfuric acid (380 g) is immersed for 5 minutes at a temperature of 68 ° C. to roughen the surface. Washed with water. Finally, after neutralizing with 35% hydrochloric acid (100 ml / L) and sufficiently removing the chromic acid used as the etching solution, Catalyst C (Okuno Pharmaceutical Co., Ltd .: tin palladium chloride complex) 30 ml / 3 and 35% 200ml / L mixed catalytic metal solution was immersed for 3 minutes under the condition of 30 ℃, and tin content was removed using 98 ℃ sulfuric acid (100ml / L) solution at 40 ℃. Further, palladium metal fine particles as a catalyst metal were adhered to the resin layer by washing with water. The same as in the first experimental example described above, (4) first plating stage, (5) second plating stage, and (6) finishing steps were sequentially performed to obtain a gasket.
[0041]
(result):
When the resistance between the opposing sides was measured while compressing the gasket thus obtained by cutting it to a length of 50 mm, the conductivity was good at a resistance value of 0.05Ω or less between 10% and 80% compression rate. Results were obtained. Further, when a combustion test was performed according to the UL94 flame retardant evaluation criteria, the flame did not ignite at all, or the flame disappeared immediately after ignition, and the evaluation was rating = V0. From these results, it is determined that the completed gasket obtained in this example has both sufficient EMI shielding properties and flame retardancy.
[0042]
【The invention's effect】
As described above, according to the present invention, a foamed elastic body made from a highly flame-retardant melamine resin is used as a core material, and a metal plating layer that imparts conductivity to the surface thereof is formed. Since the elastic body and the plating layer can be made firmly bonded by interposing the resin layer, it is possible to obtain a gasket having far higher flame retardancy than before and sufficient elasticity and electromagnetic wave shielding for use in an electronic device casing. It has the beneficial effect of being
[Brief description of the drawings]
FIG. 1 is a schematic view illustrating a highly flame-retardant electromagnetic shielding gasket according to an embodiment of the present invention with a part cut away.
FIG. 2 is a flowchart showing a method for producing a highly flame-retardant electromagnetic shielding gasket according to the present invention.
[Explanation of symbols]
10 Core material
12 Conductive coating layer
14 Resin layer
16 catalytic metal layer
18 Metal plating layer
18a First metal plating layer
18b Second metal plating layer
20 resin
24 Metal for plating

Claims (9)

A core material (10) made of a porous elastic body obtained by foaming melamine resin;
It is composed of a flame retardant and flexible conductive coating layer (12) covering the outer surface of the core material (10) ,
The conductive coating layer (12) includes a catalytic metal layer (16) having catalytic activity for a predetermined plating metal (24), and a metal plating layer (18) applied to the surface of the catalytic metal layer (16). A highly flame retardant gasket for electromagnetic wave shielding, which is bonded to the core material (10) through a resin layer (14) containing a flame retardant. The highly flame-retardant electromagnetic shielding gasket according to claim 1 , wherein the resin layer (14) is formed of a moisture curable resin . The tree layer fat (14), according to claim 1 highly flame-retardant electromagnetic shielding gasket according formed from platable synthetic resin. The metal plating layer (18) is a laminate of a first metal plating layer (18a) formed on the core material (10) side and a second metal plating layer (18b) formed on the surface side. Item 4. The highly flame-retardant electromagnetic shielding gasket according to any one of Items 1 to 3 . Create a core material (10) of a porous elastic body by foaming melamine resin,
  Forming a resin layer (14) of a moisture curable resin containing a flame retardant on the outer surface of the core (10);
  A catalytic metal layer (16) having catalytic activity for the required plating metal (24) is applied to the resin layer (14),
  Next, the metal for plating (24) is deposited on the catalyst metal layer (16) to form a metal plating layer (18).
A method for producing a highly flame-retardant electromagnetic shielding gasket. 6. The method for producing a highly flame retardant electromagnetic shielding gasket according to claim 5, wherein the moisture curable resin is a moisture curable modified silicone resin . Create a core material (10) of a porous elastic body by foaming melamine resin,
Forming a resin layer (14) of a synthetic resin capable of plating containing a flame retardant on the outer surface of the core (10),
After roughening the outer surface of the resin layer (14), a catalyst metal layer (16) having catalytic activity is applied to the required plating metal (24),
Next, the metal for plating (24) is deposited on the catalyst metal layer (16) to form a metal plating layer (18).
A method for producing a highly flame-retardant electromagnetic shielding gasket. The method for producing a highly flame-retardant electromagnetic shielding gasket according to claim 7 , wherein the plateable synthetic resin is an ABS resin . The method for producing a highly flame-retardant electromagnetic shielding gasket according to any one of claims 5 to 8, wherein the plating metal (24) forms a metal plating layer (18) by electroless plating .

Images