JP5241269B2 - Electromagnetic wave shielding gasket and flexible polyurethane foam used therefor - Google Patents

Description

The present invention relates to an electromagnetic shielding gasket and a flexible polyurethane foam used therefor (hereinafter sometimes referred to as an electromagnetic shielding foam). More specifically, the present invention relates to an electromagnetic wave shielding gasket and an electromagnetic wave shielding gasket which is used in the electromagnetic wave shielding gasket, exhibits excellent flame retardancy without using a halogen-based flame retardant, has sufficient hardness, and has a small compressive residual strain. The present invention relates to a flexible polyurethane foam that can be easily brought into close contact with a conductive cloth when used in the above-mentioned applications and maintains stable electromagnetic wave shielding performance over a long period of time.

  In recent years, in many fields such as home use, office use, industrial use, and medical use, electronic devices have been downsized and highly functionalized. Intrusion into the equipment may cause the electronic equipment to malfunction. Electromagnetic compatibility that prevents malfunction of electronic devices due to the intrusion of electromagnetic waves from the outside, that is, so-called malfunction due to electromagnetic interference waves, has become a problem, and in particular, power supply voltages used for electronic devices tend to decrease year by year. As such, the need for this electromagnetic compatibility is higher.

  In order to improve electromagnetic compatibility as described above, electromagnetic shielding gaskets are used in many electronic devices. Since this electromagnetic wave shielding gasket is disposed in a gap such as between electronic device members and used in a compressed state, the electromagnetic shielding gasket has sufficient conductivity and has good compression recovery characteristics as a mechanical property. The compression residual strain is required to be small. From such a viewpoint, conventionally, an electromagnetic shielding gasket formed by hollow extrusion molding of conductive rubber and an electromagnetic shielding gasket in which the outer peripheral surface of a flexible resin foam is covered with a conductive cloth have been used.

  However, the electromagnetic shielding gasket formed by hollow extrusion molding of conductive rubber has a problem that the electrical conductivity in the high frequency region is low and the electromagnetic shielding performance is not sufficient. Therefore, an electromagnetic wave shielding gasket in which the outer peripheral surface of the resin foam is coated with a conductive cloth having high conductivity is often used. Moreover, as a resin foam used for such an electromagnetic shielding gasket, a flexible polyurethane foam having a good compression recovery property is usually used. However, in recent years, an electromagnetic shielding gasket as an electronic device component has an excellent electromagnetic wave. Along with shielding performance, high flame retardancy has been strongly demanded.

  Therefore, in order to make flame retardant flexible polyurethane foams flame retardant, halogen flame retardants having excellent performance as flame retardants have been widely used in the past, but halogen flame retardants are environmental problems such as generation of dioxins. The use is being restricted from the aspect of. Therefore, in order to make a flexible polyurethane foam that does not use a halogen-based flame retardant and that has high flame retardancy and good compression recovery properties, expansive graphite and melamine are used in combination as a substitute for the halogen-based flame retardant. The flame retardant prescription which was made is proposed (for example, refer patent document 1).

JP 2002-198679 A

  In recent years, electronic devices have been downsized and improved in performance, and electromagnetic shielding gaskets are required to have sufficient compressibility even when compressed for a long time under high temperature and high humidity conditions. Has been. However, like the electromagnetic wave shielding gasket described in Patent Document 1, the flexible polyurethane foam containing expansive graphite and melamine is inferior in compression recovery when compressed over a long period of time under high temperature and high humidity conditions. Even when used as an electromagnetic shielding gasket, there is a problem that stable electromagnetic shielding performance cannot be maintained for a long time. In addition, not only expansive graphite and melamine, but also anti-trimonium trioxide, zinc oxide, and other conventional polyurethane foam highly flame-retardant formulations, compressed for a long time under high temperature and high humidity conditions. There is a tendency to be inferior to the compression decompression property.

The present invention has been made in view of the above-described conventional situation, and is an electromagnetic wave shielding gasket using the foam for electromagnetic wave shielding of the present invention, which can be easily brought into close contact with a conductive cloth, and is stable over a long period of time. An object of the present invention is to provide an electromagnetic shielding gasket in which electromagnetic shielding performance is maintained. Another object of the present invention is to provide a flexible polyurethane foam that exhibits excellent flame retardancy without using a halogen-based flame retardant, has sufficient hardness, has a small compressive residual strain, and is useful in electromagnetic wave shielding gasket applications. And

The present invention is as follows.
1. An electromagnetic shielding gasket comprising a gasket foam made of a flexible polyurethane foam for an electromagnetic shielding gasket and a conductive cloth covering an outer peripheral surface of the gasket foam, wherein the gasket foam comprises a polyol, a polyisocyanate, and a phosphorus-based difficulty. A foam raw material containing a flame retardant and water is foamed and cured. When the polyol contains a polymer polyol and the polyol is 100% by mass, the polymer polyol is 25 to 75% by mass, When the said polyol is 100 mass%, the said phosphorus flame retardant is 4-23 mass%, and when this phosphorus flame retardant is 100 mass%, phosphorus contained in this phosphorus flame retardant is 12 to 20 wt%, and 100 parts by mass of the polyol of the foam in the raw material When the above water is 0.9 to 3.5 parts by weight, density measured by JIS K 7222 is 30~100kg / ^{m 3,} the hardness was measured by JIS K 6400-2 6.7 D Method The test piece having a thickness of 150 to 400 N and a thickness of 5 mm was compressed by 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, the residue measured by the JIS K 6400-4 4.5.2 A method An electromagnetic wave shielding gasket having a strain of 15% or less.
2. The above 1. wherein the phosphorus flame retardant is a phosphate ester flame retardant. An electromagnetic shielding gasket according to 1.
3. A flexible polyurethane foam for electromagnetic shielding gaskets, used in electromagnetic shielding gaskets together with a conductive cloth covering its outer peripheral surface. Foam raw material containing polyol, polyisocyanate, phosphorus flame retardant, and water is foamed. Cured,
The polyol contains a polymer polyol. When the polyol is 100% by mass, the polymer polyol is 25 to 75% by mass. When the polyol is 100% by mass, the phosphorus flame retardant is 4%. When the phosphorus flame retardant is 100% by mass, the phosphorus contained in the phosphorus flame retardant is 12 to 20% by mass, and the polyol in the foam raw material is 100% by mass. In the case of parts by mass, the water is 0.9 to 3.5 parts by mass, the density measured according to JIS K 7222 is 30 to 100 kg / m ³ , and according to JIS K 6400-2 6.7 D method. The measured hardness is 150 to 400 N, and a test piece having a thickness of 5 mm is compressed by 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, JIS K 6400-4 4.5. 2 A flexible polyurethane foam characterized by having a residual strain measured by the A method of 15% or less.

The electromagnetic wave shielding gasket of the present invention comprises a gasket foam made of the electromagnetic wave shielding foam of the present invention, which exhibits excellent flame retardancy and has sufficient hardness and low compression residual strain. In this case, the gasket foam and the conductive cloth are not peeled off, the excellent conductivity of the conductive cloth is maintained, and the stable electromagnetic shielding performance is maintained for a long time.
Moreover, when a phosphorus flame retardant is a phosphate ester flame retardant, it can be set as the electromagnetic wave shielding gasket which has the more outstanding flame retardance by mixing | blending a predetermined amount.
In the flexible polyurethane foam of the present invention, since a predetermined amount of a phosphorus-based flame retardant containing a required amount of phosphorus is blended, excellent flame retardancy is exhibited, and it has sufficient hardness and has a compressive residual strain. When used for an electromagnetic wave shielding gasket, it is excellent in adhesion to a conductive cloth and maintains a stable electromagnetic wave shielding performance over a long period of time. Further, in this electromagnetic wave shielding foam, the phosphorus-based flame retardant does not contain halogen, which is preferable from the viewpoint of the environment. Furthermore, since it is not necessary to add a large amount of phosphorus-based flame retardant, the compression residual strain does not increase, and stable electromagnetic shielding performance is maintained for a long period.
Further, since hardness measured by JIS K 6400-2 6.7 D method is 150～400N, can be easily adhered to the conductive cloth, and electromagnetic shielding gasket is pressed, conductive cloth when deformed It is also excellent in adhesiveness, particularly in the initial stage, and more stable electromagnetic shielding performance is maintained over a long period of time.
Furthermore, a test piece having a thickness of 5 mm was compressed 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, the residual strain measured by the JIS K 6400-4 4.5.2 A method was 15% or less. some reason, can be easily adhered to the conductive cloth, is and pressed electromagnetic shielding gasket, excellent initial and long term adhesion to the conductive fabric when deformed, particularly stable electromagnetic wave shielding performance over a long term Maintained.

The present invention will be described in detail below.
[1] Soft polyurethane foam for electromagnetic shielding gasket The electromagnetic shielding foam of the present invention is obtained by foaming and curing a foam raw material containing a polyol, a polyisocyanate, and a phosphorus-based flame retardant. In the case where the polymer polyol is contained in an amount of 25 to 75% by mass and the polyol is 100% by mass, the phosphorus flame retardant is 4 to 23% by mass and the phosphorus flame retardant is 100% by mass. In this case, phosphorus contained in the phosphorus-based flame retardant is 12 to 20% by mass, and the density measured according to JIS K 7222 is 30 to 100 kg / m ³ .

The above “soft polyurethane foam for electromagnetic wave shielding” has a density of 30 to 100 kg / m ³ measured according to JIS K 7222. This density is preferably 40 to 100 kg / m ³ , particularly preferably 60 to 100 kg / m ³ . When the density is from 30 to 100 kg / m ³ , the electromagnetic shielding foam having a small compressive residual strain and sufficient hardness can be obtained.

Moreover, the hardness of the foam for electromagnetic wave shields measured by JIS K 6400-2 6.7 D method is 150-400N . The hardness is more preferably 200 to 400N, particularly 300 to 400N. When the hardness of the electromagnetic shielding foam is 150 to 400 N, it can be easily adhered to the conductive cloth, and the adhesiveness to the conductive cloth when the electromagnetic shielding gasket is pressed and deformed, particularly the initial adhesion. And more stable electromagnetic shielding performance is maintained over a long period of time.

Further, a test piece having a thickness of 5 mm was compressed by 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, the compression residual of the foam for electromagnetic wave shielding measured by JIS K 6400-4 4.5.2 A method The strain is 15% or less . The compressive residual strain is more preferably 10% or less. If the compressive residual strain of the electromagnetic shielding foam is 15% or less, it can be easily brought into close contact with the conductive cloth, and the adhesiveness with the conductive cloth when the electromagnetic shielding gasket is pressed and deformed, particularly in the initial and long term. It has excellent adhesion and maintains particularly stable electromagnetic shielding performance over a long period of time.

The “polyol” contains a predetermined amount of polymer polyol. Other polyols used in combination with this polymer polyol are not particularly limited, and various polyols can be used. Examples of other polyols include polyether polyols, polyester polyols, and polyether ester polyols, and polyether polyols are particularly preferable.
Other polyols may be used alone or in combination of two or more. Different types of polyols such as polyether polyols, polyester polyols, polyether ester polyols and the like can also be used in combination.

  The above-mentioned “polymer polyol” is contained in the polyol. As the polymer polyol, a polyol obtained by graft polymerization of a vinyl compound such as acrylonitrile, styrene, or methyl (meth) acrylate on a polyether polyol can be used. The content of the polymer polyol is 25 to 75% by mass, preferably 30 to 50% by mass, when the total amount of polyol is 100% by mass. As the content of the polymer polyol increases, the hardness of the foam for electromagnetic wave shielding increases. On the other hand, the compression residual strain also tends to increase, so it is possible to set the hardness and the compression residual strain in consideration. preferable.

The amount of the vinyl compound used for producing the polymer polyol is not particularly limited, but when the polymer polyol is 100% by weight, 10 to 50% by weight of the vinyl compound is often used. In order to improve the hardness of the foam for electromagnetic wave shielding, a polymer polyol in which the amount of vinyl compound used is 20% by weight or more is preferable.
Only one type of polymer polyol may be used, or two or more types may be used in combination.

Polyisocyanate is not particularly limited, and polyisocyanate generally used in the production of flexible polyurethane foam can be used. As this polyisocyanate, toluene diisocyanate (TDI), crude TDI, 4,4′-diphenylmethane diisocyanate (MDI), crude MDI, and aromatic polyisocyanates such as 1,5-naphthalene diisocyanate and paraphenylene diisocyanate should be used. Can do. In addition, aliphatic polyisocyanates such as hexamethylene diisocyanate, hydrogenated MDI, and isophorone diisocyanate can also be used. In addition to these, a prepolymer type polyisocyanate can also be used.
Only one type of polyisocyanate may be used, or two or more types may be used in combination, but only one type is often used.
Moreover, a polyol and polyisocyanate can be used in the mass ratio from which an isocyanate index becomes 100-120.

  The combination of the polyol and the polyisocyanate is not particularly limited, but a bifunctional polyol such as ethylene glycol and a trifunctional or higher functional polyol such as trimethylolpropane may be used in combination as a polyol starting material, and TDI may be used as the polyisocyanate. preferable. When a tri- or higher functional polyol such as trimethylolpropane is used as a starting material, more cross-linked structure can be introduced into the foam for electromagnetic wave shielding, in addition to a predetermined density, compression residual strain, etc., sufficient elongation and It can be set as the electromagnetic shielding foam which has tensile strength etc.

  Phosphorus flame retardants include halogen-containing types containing halogens such as chlorine and bromine, and halogen-free types that do not contain halogens. However, since halogens have environmental problems, the electromagnetic wave shield of the present invention Halogen-free type is used for the foam for use. As the “phosphorous flame retardant”, organic phosphorous compounds such as phosphoric acid esters and polyphosphoric acids are used, and among these, phosphoric acid ester flame retardants are preferable. When this phosphate ester flame retardant is used, the viscosity of the foam stock solution can be kept low, the stirring efficiency can be improved, and a homogeneous electromagnetic shielding foam can be obtained. The phosphorus-based flame retardant is preferably an unreactive additive-type phosphorus-based flame retardant than the reactive type, and more preferably an additive-type phosphate-based flame retardant.

Examples of phosphate ester flame retardants include trimethyl phosphate, triethyl phosphate, tributyl phosphate, triisobutyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, cresyl di-2,6-xylate. Nyl phosphate and the like can be mentioned.
Only one type of phosphorus-based flame retardant may be used, or two or more types may be used in combination.

  Furthermore, the compounding quantity of a phosphorus flame retardant is 4-23 mass% when a polyol is 100 mass%, and it is preferable that it is 5-20 mass%, especially 7-15 mass%. When the blending amount of the phosphorus-based flame retardant is less than 4% by mass, the foam for electromagnetic wave shield having sufficient flame retardancy cannot be obtained. On the other hand, if the blending amount of the phosphorus flame retardant exceeds 23% by mass, the compressive residual strain becomes large, and the electromagnetic shielding performance deteriorates when used over a long period of time.

Moreover, the phosphorus contained in a phosphorus flame retardant is 12-20 mass% when a phosphorus flame retardant is 100 mass%, and it is preferable that it is 14-18 mass%. If the phosphorous content in the phosphorous flame retardant is less than 12% by mass, it is necessary to add a large amount of phosphorous flame retardant in order to obtain an electromagnetic shielding foam having excellent flame retardancy. In addition, the compressive residual strain increases and the hardness decreases, and the electromagnetic shielding performance decreases when used over a long period of time.
In addition, if the phosphorus contained in the phosphorus-based flame retardant is 12 to 20% by mass, the foam for electromagnetic wave shielding has excellent flame retardancy, small compression residual strain, and sufficient hardness. be able to.

  Other flame retardants can be blended and used in combination with the phosphorus-based flame retardant as long as the excellent flame retardancy, compression residual strain, hardness, electromagnetic wave shielding performance and the like of the foam for electromagnetic wave shielding are maintained. As other flame retardants, for example, various non-halogen flame retardants can be used. Examples of the non-halogen flame retardant include aluminum hydroxide, aluminum oxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, hydrotalcite, antimony trioxide, ammonium polyphosphate, calcium carbonate, activated carbon and the like. Of these, aluminum hydroxide, antimony trioxide, ammonium polyphosphate and calcium carbonate are preferred. These flame retardants can be easily mixed with other raw materials for producing the electromagnetic shielding foam, and can sufficiently improve the flame retardancy even if the blending amount is small. Further, the influence on other physical properties such as elongation and tensile strength is small, which is advantageous from this viewpoint.

  In addition to polyols, polyisocyanates, and phosphorus-based flame retardants, the above-mentioned “foam raw material” contains a foaming agent, a catalyst, a foam stabilizer, a crosslinking agent, and the like. In addition, an ultraviolet absorber, an antioxidant, an organic filler Inorganic fillers, colorants, plasticizers and the like can also be blended. These other components are usually blended in advance with a polyol, and then the polyol component and polyisocyanate are mixed, foamed and cured to produce an electromagnetic shielding foam.

Water is used as the foaming agent. This water is not particularly limited, and various waters such as ion exchange water, tap water, and distilled water can be used. The amount of water used in the production of the electromagnetic shielding foam is 0.9 to 3.5 parts by mass, particularly 1.5 to 3 parts by mass, when the polyol is 100 parts by mass. Part. If water from 0.9 to 3.5 mass parts, given density, the foam for electromagnetic shielding having a compressive residual strain and hardness, etc. can be easily produced.

As the catalyst, amine-based catalysts such as tertiary amine compounds such as triethylamine, triethylenediamine, N-methylmorpholine dimethylaminomethylphenol, imidazole, and 1,8-diazabicyclo [5,4,0] undecene can be used. Further, organic tin compounds such as stannous octoate, dibutyltin diacetate, dibutyltin dilaurate, organic nickel compounds such as nickel acetylacetonate and nickel diacetylacetonate, alkali metal or alkaline earth metal alkoxides such as sodium acetate, phenoxide In addition, metal catalysts such as octyl zinc can also be used.
Only one type of catalyst may be used, or two or more types may be used in combination. An amine catalyst and a metal catalyst may be used in combination. The usage-amount of a catalyst can be 0.5-1.5 mass parts when a polyol is 100 mass parts.

As the foam stabilizer, generally, a block copolymer of dimethylpolysiloxane and polyether can be used. A special foam stabilizer in which an organic functional group is added to polysiloxane can also be used. Thus, a silicone type foam stabilizer is often used as the foam stabilizer.
Only one type of foam stabilizer may be used, or two or more types may be used in combination. The amount of the foam stabilizer used can be 0.5 to 1.5 parts by mass when the polyol is 100 parts by mass.

  A crosslinking agent can also be mix | blended with a foam raw material. As this crosslinking agent, short-chain diols such as ethylene glycol, propylene glycol, and 1,4-butanediol can be used. Furthermore, short-chain diamines such as ethylenediamine, tetramethylenediamine, and hexamethylenediamine, and amine compounds such as triethanolamine, triisopropanolamine, and diisopropanolamine can also be used.

  As UV absorbers, antioxidants, organic fillers, inorganic fillers, colorants, plasticizers and the like, those generally used by blending with foam raw materials for producing flexible polyurethane foams can be appropriately used.

  The method for producing the electromagnetic shielding foam is not particularly limited, and can be produced by stirring, mixing, reacting and curing the polyisocyanate and the polyol component. Moreover, a slab foam may be sufficient and a mold foam may be sufficient. The foam raw material contains the above-described various components, but TDI is particularly frequently used in slab foam, and in some cases, a mixture of TDI and MDI, or a modified product such as MDI or TDI can be used.

[2] Electromagnetic shielding gasket The electromagnetic shielding gasket of the present invention includes a gasket foam made of the electromagnetic shielding foam of the present invention, and a conductive cloth covering the outer peripheral surface of the gasket foam.
In addition to the gasket foam and the conductive cloth, this electromagnetic shielding gasket is provided with, for example, an acrylic adhesive for bonding the ends of the conductive cloth or for bonding the conductive cloth and the gasket foam. You may provide the joining layer and acrylic adhesive tape which are used.

  The method of making the electromagnetic shielding foam into the above-mentioned “gasket foam” is not particularly limited, and examples thereof include a method of cutting out a foam having a predetermined shape and size from the electromagnetic shielding foam by scratching and tapping. Moreover, the method etc. which process the foam raw material which carried out the said skid and the tapping process to predetermined thickness by hot press processing, etc. are mentioned.

  As the “conductive cloth”, a conductive cloth usually used for an electromagnetic shielding gasket can be used without any particular limitation. As the conductive cloth, a conductive cloth obtained by performing metal plating on a woven cloth made of organic fibers is preferable from the viewpoint that it has excellent compressibility and is inexpensive. More specifically, it is more preferable to use a conductive cloth obtained by performing copper plating on a woven cloth made of synthetic fibers such as polyester and further performing nickel plating or silver plating on the surface of the copper plating. Thus, when nickel plating or silver plating is applied to the surface, durability in an atmosphere such as heating and humidification is improved, and a decrease in conductivity of the electromagnetic shielding gasket is suppressed.

  The method for coating the outer peripheral surface of the gasket foam with a conductive cloth is not particularly limited. For example, an adhesive is applied to the outer peripheral surface of the gasket foam and / or the inner surface of the conductive cloth, and the conductive cloth is wound around the gasket foam. Then, it heats as needed, a conductive cloth can be joined to the outer peripheral surface of the foam for gaskets, and it can coat | cover. Furthermore, if the conductive cloth is relatively elastic, the conductive cloth can be folded in a U-shaped cross section and covered with a gasket foam. In addition, the overlapping part of both ends of the conductive cloth is fixed by sticking one side such as a double-sided adhesive tape, and by sticking the other side such as this double-sided adhesive tape to a place where an electromagnetic shielding gasket is used An electromagnetic shielding gasket can be provided. Further, a flame-retardant backing sheet can be disposed between the gasket foam and the conductive cloth. By disposing the backing sheet in this manner, an electromagnetic wave shielding gasket having higher flame retardancy and excellent adhesion between the gasket foam and the conductive cloth can be obtained.

  The shape and size of the electromagnetic shielding gasket are preferably set as appropriate depending on the shape and size of the portion to be used. For example, as shown in FIG. 1, a long body having a substantially rectangular cross section in which corners of four corners are arcuate. Further, when a pressing force is applied to such an electromagnetic shielding gasket, when the electromagnetic shielding foam has sufficient hardness and the compression residual strain is small, the gasket foam is not deformed, and the gasket foam It does not peel off while keeping in close contact with the conductive cloth. On the other hand, when the hardness of the electromagnetic shielding foam is small, the initial adhesion between the gasket foam and the conductive cloth when a pressing force is applied to the gasket foam decreases. Moreover, when the hardness of the electromagnetic shielding foam is small, especially when the hardness is small and the compression residual strain is large, the gasket foam is bent and deformed in the direction in which the pressing force is applied, as shown in FIG. The foam for gasket and the conductive cloth are peeled off, and the conductivity of the electromagnetic shielding gasket is lowered.

Hereinafter, the present invention will be described specifically by way of examples.
Examples 1-9 and Comparative Examples 1-8
The foam raw materials described in Table 1 (Examples 1 to 9) and Table 2 (Comparative Examples 1 to 8) were put into a rectangular container having a length of 270 mm, a width of 270 mm, and a height of 200 mm, and naturally foamed. Then, it accommodated in the drying furnace and left still at 80 degreeC for 15 minutes, and reaction was completed. Subsequently, it was left to stand at room temperature (25 ° C.) for 24 hours, and then a test piece having a predetermined size for evaluating the following physical properties and the like was cut out from the generated electromagnetic shielding foam.

[1] Raw material (1) Polyol Polyol 1; Polyether polyol (manufactured by Mitsui Takeda, trade name “L-50”, number of functional groups 3, hydroxyl value 56.1 mgKOH / mg)
Polyol 2; Polymer polyol (Asahi Glass Co., Ltd., trade name “EXCENOL 941 WB”, functional group number 3, hydroxyl value 32 mgKOH / mg)
(2) Polyisocyanate TDI-65 (made by Nippon Polyurethane Industry Co., Ltd., trade name “T-65”)
(3) Catalyst Amine-based catalyst; cyclic diamine (manufactured by Air Products Japan, trade name “DABCO 33-LV”)
Tin-based catalyst; Stanas octoate (Johoku Chemical Co., Ltd., trade name “MRH-110”)
(4) Foam stabilizer: Silicone foam stabilizer (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “F-650A”)
(5) Flame retardant Liquid flame retardant 1; condensed phosphate ester flame retardant (manufactured by Akzo Nobel, trade name “Phyrol PNX-S”, phosphorus content 16.8% by mass)
Liquid flame retardant 2; condensed phosphate ester flame retardant (manufactured by Daihachi Chemical Co., Ltd., trade name “DAIGUARD-880”, phosphorus content 15.1% by mass)
Liquid flame retardant 3; condensed phosphate ester flame retardant (manufactured by Daihachi Chemical Co., Ltd., trade name “CDP”, phosphorus content 9.1 mass%)
Powdered flame retardant 1; Melamine powder (manufactured by Nissan Chemical Co., Ltd., trade name “melamine”)
Powdered flame retardant 1; expanded graphite (manufactured by Sumikin Kako, trade name “80LTE-UN”)

[2] Evaluation method (1) Density (kg / m ³ ); measured according to JIS K 7222 (2) Hardness (N); measured according to JIS K 6400-2 6.7 D method (3 ) Flame retardancy; measured in accordance with UL-94 HF-2 test method and UL-94 HBF test method with test piece thickness of 6 mm. (4) 50% compression residual strain after wet heat; 70 mm test piece with thickness of 70 mm Compressed by 50% in an atmosphere of 50 ° C. and 50% RH, and measured the residual strain according to JIS K 6400-4 4.5.2 A after 24 hours. (5) Adhesiveness with conductive cloth Initial stage after compression Conductive cloth adhesiveness: The gasket foam was covered with a conductive cloth, and this structure was repeatedly compressed to a thickness of about 1/4 of the original thickness. After this compression is repeated 50 times, the structure is visually observed to confirm whether there is a gap between the gasket foam and the conductive cloth. After compression, long-term conductive cloth adhesion; Cover, compress 50% in an atmosphere of 70 ° C. and 50% RH, and measure the residual strain according to JIS K 6400-4 4.5.2 A after 24 hours. Evaluation results for each item Are as shown in Tables 1 and 2. In addition, the evaluation standard of the initial conductive cloth adhesion after compression in Table 1 and Table 2 is X when the gap is observed remarkably, and is otherwise ◯, and the evaluation standard of the long-term conductive cloth adhesion after compression is When the residual strain is less than 20%, ◯, and when it exceeds 20%, it is ×.
In addition, this adhesiveness also becomes evaluation of the recoverability from the deformation | transformation by compression of a conductive cloth with comparatively high rigidity. Therefore, in addition to the distortion characteristics of the foam for gaskets, the influence of hardness is also great, and even if the distortion characteristics are good, if the hardness is small, it may not necessarily be an electromagnetic shielding gasket with excellent adhesion. is there.

According to the results of Table 1, Examples 1 to 9 using foam raw materials containing a predetermined amount of a polymer polyol as a polyol and a required amount of a condensed phosphate ester flame retardant containing a predetermined amount of phosphorus. In the above, an electromagnetic shielding foam having a predetermined density, a small compressive residual strain, and a sufficient hardness has been produced, and the evaluation result of flame retardancy is acceptable, and the gasket foam after compression It can be seen that the adhesion between the film and the conductive cloth is excellent both in the initial and long term. In particular, in Examples 1, 2, 6, and 8 in which the blending amount of the liquid flame retardant 1 is 7.5 parts by mass or 5 parts by mass and the density is 73.6 to 96.3 kg / m ³ , the compression residual An electromagnetic wave shielding foam having a smaller strain of 3.4 to 6.7% and a larger hardness of 325.1 to 376.1 N can be obtained.
In addition, since the compounding quantity of a flame retardant is smaller than Example 8 in Example 8, the tendency for a flame retardance to fall is seen.

  On the other hand, according to the results in Table 2, in Comparative Example 1 in which the density is too small, the compressive residual strain is large and the hardness is small, and the adhesion between the gasket foam and the conductive cloth is lowered. Further, in Comparative Example 2 in which the density is excessive, although the compression residual strain is small, the hardness is large, and the adhesiveness is excellent, the same flame retardant as in Comparative Example 1 is blended in the same amount, Flame retardance is unacceptable. Furthermore, in Comparative Example 3 in which the polymer polyol is not used, the hardness is small and the adhesion is lowered.

  Moreover, in the comparative example 4 with which the compounding quantity of the liquid flame retardant 1 is too small, flame retardance is unacceptable, and in the comparative example 5 which is excessive, adhesiveness falls. Furthermore, in Comparative Example 6 using the powdered flame retardants 1 and 2, since the flame retardant is excessive, the compression residual strain is large and the adhesion is lowered. Moreover, in Comparative Example 7 using the liquid flame retardant 3 having a low phosphorus content, although there is no problem in adhesion, the flame retardant is unacceptable, and in Comparative Example 8 in which the liquid flame retardant 3 is increased, it is difficult. Although there is no problem with flammability, adhesion is reduced. Thus, it can be seen that the gasket foam of the comparative example cannot achieve both flame retardancy and adhesion.

It is a schematic diagram of the cross section of an electromagnetic wave shielding gasket. It is a schematic diagram for demonstrating a mode that the outer peripheral surface of the foam for gaskets and the inner surface of the electrically conductive cloth were separated when the pressing force was applied, and a gap was generated.

Explanation of symbols

  1; foam for gasket; 2; conductive cloth; 3; double-sided adhesive tape;

Claims (3)

In an electromagnetic shielding gasket comprising a foam for a gasket made of a flexible polyurethane foam for an electromagnetic shielding gasket, and a conductive cloth covering an outer peripheral surface of the gasket foam,
The above foam for a gasket is obtained by foaming and curing a foam raw material containing a polyol, a polyisocyanate, a phosphorus flame retardant, and water,
The polyol contains a polymer polyol, and when the polyol is 100% by mass, the polymer polyol is 25 to 75% by mass,
When the said polyol is 100 mass%, the said phosphorus flame retardant is 4-23 mass%, and when this phosphorus flame retardant is 100 mass%, phosphorus contained in this phosphorus flame retardant Is 12-20% by weight,
When the polyol in the foam raw material is 100 parts by mass, the water is 0.9 to 3.5 parts by mass,
The density measured according to JIS K 7222 is 30 to 100 kg / m ³ ,
The hardness measured by JIS K 6400-2 6.7 D method is 150-400N,
A test piece having a thickness of 5 mm is compressed by 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, the residual strain measured by the JIS K 6400-4 4.5.2 A method is 15% or less. An electromagnetic shielding gasket characterized by   The electromagnetic wave shielding gasket according to claim 1, wherein the phosphorus flame retardant is a phosphate ester flame retardant. A flexible polyurethane foam for electromagnetic shielding gaskets,
Used for electromagnetic shielding gasket together with conductive cloth covering its outer peripheral surface,
Foam raw material containing polyol, polyisocyanate, phosphorus flame retardant and water is foamed and cured,
The polyol contains a polymer polyol, and when the polyol is 100% by mass, the polymer polyol is 25 to 75% by mass,
When the said polyol is 100 mass%, the said phosphorus flame retardant is 4-23 mass%, and when this phosphorus flame retardant is 100 mass%, phosphorus contained in this phosphorus flame retardant Is 12-20% by weight,
When the polyol in the foam raw material is 100 parts by mass, the water is 0.9 to 3.5 parts by mass,
The density measured according to JIS K 7222 is 30 to 100 kg / m ³ ,
The hardness measured by JIS K 6400-2 6.7 D method is 150-400N,
A test piece having a thickness of 5 mm is compressed by 50% in an atmosphere of 70 ° C. and 50% RH, and after 24 hours, the residual strain measured by the JIS K 6400-4 4.5.2 A method is 15% or less. Flexible polyurethane foam characterized by

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