Seal material

Abstract

To provide a novel seal material exhibiting excellent adhesion (sealability) at a low surface pressure.SOLUTION: A seal material includes: an elastic layer including a foamed rubber layer; and adhesive layers respectively laminated and disposed on both main surfaces of the elastic layer, where the foamed rubber layer comprises a foamed product of an unfoamed rubber layer including a rubber constituent of an ethylene propylene diene ternary copolymer (EPDM), a cross-linking agent, a cross-linking accelerator, and a gas generating agent, the cross-linking agent is a phenol resin cross-linking agent, and the cross-linking accelerator is an organic sulfonic acid compound.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing material.

Background Art

[0002] Conventionally, rubber foams have been used as sealing materials for various industrial products such as automobiles, vehicles, ships, and various electrical and electronic devices for the purposes of dust prevention, heat insulation, sound insulation, vibration prevention, buffering, waterproofing, and confidentiality. For example, in the automotive field, the demand for sealing materials used in electrical and electronic component protection cases and the like has been rapidly increasing at the accommodation sites of various electrical and electronic devices that make up hybrid vehicles and electric vehicles. As an example of a sealing material used in a part configured by fastening a pair of flanges with low rigidity with small bolts like the above-mentioned electrical component protection case, those made of rubber foam having a foamed rubber layer on one or both sides of a base material made of a metal plate or the like can be mentioned (see Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a part configured by fastening a pair of flanges with low rigidity with small bolts like the above-mentioned electrical component protection case, it is required to exhibit sufficient sealing performance due to the low tightening surface pressure generated between the bolts due to the undulation of the flanges.

[0005] However, when using, as a sealing material made of a rubber foam, one having a foamed rubber layer on a base material made of the above-described metal plate or the like, for example, when the fluid to be sealed penetrates between the base material made of a metal plate and the foamed rubber layer, the adhesion between the two may decrease, and the sealing performance may decrease.

[0006] On the other hand, when increasing the tightening load of the flange to increase the tightening surface pressure, the components may be damaged when vibration or impact is applied during tightening or during operation after tightening.

[0007] For this reason, as a sealing material used for an electrical component protection case or the like, one that exhibits excellent sealing performance at a low surface pressure has been demanded.

[0008] In addition, as a sealing material, a sealing material for water stop provided inside an automobile door is known. The above-described sealing material for water stop is disposed in a compressed state inside the automobile door, and is in a state where it is easily subjected to intermittent impacts due to vibration during opening and closing of the door or during operation. For this reason, as a sealing material for water stop provided inside an automobile door, one that exhibits excellent sealing performance at a low surface pressure has also been demanded.

[0009] Furthermore, as a sealing material, a sealing material for water stop provided in various electronic devices such as portable terminals such as mobile phones and tablets and in-vehicle electronic devices is known. The above-described sealing material is disposed in a compressed state inside the electronic device, and is in a state where it is easily subjected to intermittent impacts due to vibration during use or operation. For this reason, as a sealing material for water stop provided inside an electronic device, one that exhibits excellent sealing performance at a low surface pressure has also been demanded.

[0010] Under such circumstances, an object of the present invention is to provide a novel sealing material that exhibits high adhesion (sealing performance) at a low surface pressure.

Means for Solving the Problems

[0011] In order to achieve the above object, as a result of intensive studies by the present inventors, it has been found that the above technical problem can be solved by a sealing material having an elastic layer composed of a specific foamed rubber layer and adhesive layers laminated and disposed on both main surfaces of the elastic layer, and the present invention has been completed based on this finding.

[0012] That is, the present invention is (1) having an elastic layer including a foamed rubber layer and adhesive layers laminated and disposed on both main surfaces of the elastic layer, wherein the foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent, and the crosslinking accelerator is an organic sulfonic acid compound characterized sealing material, (2) The sealing material according to (1) above, wherein the content ratio of the phenolic resin crosslinking agent in the unfoamed rubber layer is 2.0 to 20.0% by mass in terms of solid content, (3) The sealing material according to (1) or (2) above, wherein the elastic layer is composed of only the foamed rubber layer or a laminated integrated product in which the foamed rubber layer is laminated and disposed on both main surfaces of a base material layer made of a metal plate or a resin plate, (4) The sealing material according to any one of (1) to (3) above, wherein the amount of diene constituting the ethylene-propylene-diene terpolymer (EPDM) is 1 to 20% by mass, (5) The sealing material according to any one of (1) to (4) above, wherein the foamed rubber layer is a foam having a foaming ratio of 1.5 times or more of the unfoamed rubber layer, (6) The sealing material according to any one of (1) to (5) above, wherein the adhesive layer contains at least one selected from urethane resin, natural rubber, butadiene rubber, isoprene rubber, styrene butadiene, nitrile rubber, ethylene-propylene-diene terpolymer, butyl rubber, chloroprene rubber, thermoplastic elastomer, and any water addition product thereof as an adhesive, (7) The sealant according to (6) above, wherein the thermoplastic elastomer is at least one selected from styrenic elastomers, olefinic thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers which provides the same.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a novel sealant that exhibits high adhesion (sealing property) at low surface pressure.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] The sealant according to the present invention has an elastic layer including a foamed rubber layer, and adhesive layers laminated on both main surfaces of the elastic layer, respectively. The foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent. The crosslinking accelerator is an organic sulfonic acid compound and is characterized by this.

[0016] The sealant according to the present invention has a laminated structure including an elastic layer and adhesive layers laminated on both main surfaces of the elastic layer, respectively.

[0017] In the sealant according to the present invention, the elastic layer includes a foamed rubber layer.

[0018] In the sealing material according to the present invention, as the form of the elastic layer, in addition to the form consisting only of a foamed rubber layer (hereinafter referred to as the first form), a form consisting of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a metal plate or a resin plate (hereinafter referred to as the second form) can be mentioned.

[0019] Figure 1 is a schematic diagram of a vertical cross-section in an example form of the sealing material according to the present invention, showing an example form when the elastic layer adopts the first form. In the example form shown in Figure 1, the sealing material 1 includes an elastic layer i consisting only of a foamed rubber layer r, and adhesive layers s, s laminated and arranged on both main surfaces of the elastic layer i, respectively.

[0020] Further, Figure 2 is a schematic diagram of a vertical cross-section in another example form of the sealing material according to the present invention, showing an example form when the elastic layer adopts the second form. In Figure 2, the sealing material 1 includes an elastic layer i composed of a laminated integrated body of a base material layer b made of a metal plate or a resin plate and foamed rubber layers r, r laminated and arranged on both main surfaces of the base material layer, and adhesive layers s, s laminated and arranged on both main surfaces of the elastic layer i, respectively.

[0021] In the sealing material according to the present invention, the elastic layer preferably has a thickness of 300 to 800 μm, and more preferably 400 to 700 μm.

[0022] The thickness of the elastic layer means the arithmetic average value when the thicknesses at 10 locations are measured using a dial gauge.

[0023] In the sealing material according to the present invention, when the elastic layer adopts the first form, that is, the form consisting only of a foamed rubber layer, the thickness of the elastic layer corresponds to the thickness of the foamed rubber layer.

[0024] In the sealing material according to the present invention, when the elastic layer adopts the first form, that is, the form consisting only of a foamed rubber layer, the thickness of the elastic layer corresponds to the thickness of the foamed rubber layer. In the sealing material according to the present invention, when the elastic layer adopts the second form, that is, a form composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a metal plate or a resin plate, the thickness of the elastic layer corresponds to the total thickness of the base material layer made of a metal plate or a resin plate and the thickness of the foamed rubber layer.

[0025] In the sealing material according to the present invention, the foamed rubber layer constituting the elastic layer is composed of a foam of an unfoamed rubber layer.

[0026] In the sealing material according to the present invention, the foamed rubber layer is preferably a foam with a foaming ratio of 1.5 times or more of the unfoamed rubber layer, more preferably a foam with a foaming ratio of 2.0 times or more of the unfoamed rubber layer, and even more preferably a foam with a foaming ratio of 2.5 times or more of the unfoamed rubber layer. The upper limit of the foaming ratio of the unfoamed rubber layer is not particularly limited, but the foaming ratio of the unfoamed rubber is usually 6.0 times or less.

[0027] In the sealing material according to the present invention, when the foaming ratio of the unfoamed rubber layer is 1.5 times or more, excellent adhesion (sealing property) can be easily exhibited even when the surface pressure is low.

[0028] In this application document, the above foaming ratio means a value calculated by the following formula. Foaming ratio = Thickness of the foamed rubber layer / Thickness of the unfoamed rubber layer (However, the thickness of the foamed rubber layer means the arithmetic mean value when the thicknesses at 10 locations are measured using a dial gauge, and the thickness of the unfoamed rubber layer also means the arithmetic mean value when the thicknesses at 10 locations are measured using a dial gauge.)

[0029] In the sealing material according to the present invention, the foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent.

[0030] As the above ethylene-propylene-diene terpolymer (EPDM), those having a diene content of 1 to 20% by mass in the EPDM are preferred, and those having a diene content of 5 to 15% by mass are more preferred.

[0031] When the diene content in the EPDM is within the above range, it is possible to easily impart the desired resistance to sagging to the foamed rubber layer.

[0032] By containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component in the unfoamed rubber layer, a foamed rubber layer having desired properties can be easily obtained.

[0033] The unfoamed rubber layer preferably contains 10 to 90% by mass, more preferably 30 to 70% by mass, of the ethylene-propylene-diene terpolymer (EPDM) in terms of solid content.

[0034] When the unfoamed rubber layer contains the above ethylene-propylene-diene terpolymer (EPDM) in the above ratio, it is possible to easily provide a sealing material excellent in adhesion (sealing property) and resilience.

[0035] Further, in the sealing material according to the present invention, the above unfoamed rubber layer contains a phenolic resin crosslinking agent as a crosslinking agent.

[0036] The unfoamed rubber layer preferably contains 2.0 to 20.0% by mass, more preferably 2.6 to 17.5% by mass, of the phenolic resin crosslinking agent in terms of solid content.

[0037] When the unfoamed rubber layer contains the above phenolic resin crosslinking agent in the above ratio, it is possible to easily control the flexibility of the foamed rubber layer and easily provide a sealing material excellent in adhesion (sealing property) and resilience.

[0038] In the sealing material according to the present invention, the above unfoamed rubber layer contains an organic sulfonic acid compound as a crosslinking accelerator. Examples of the organic sulfonic acid compound include one or more selected from methanesulfonic acid (MSA), benzenesulfonic acid (BSA), trifluoromethanesulfonic acid (TFMSA), p-toluenesulfonic acid (PTSA), heptafluoropropanesulfonic acid, heptadecafluorooctanesulfonic acid, naphthalenesulfonic acid (NSA), naphthalenedisulfonic acid (NDSA), methanedisulfonic acid (MDSA), ethanedisulfonic acid (EDSA), nonafluorobutanesulfonic acid (FBSA), bis(nonafluorobutanesulfonyl)imide (BFBSI), dinonylnaphthalenesulfonic acid (DNNSA), dinonylnaphthalenedisulfonic acid (DNNDSA), dodecylbenzenesulfonic acid (DDBSA), ethanesulfonic acid (ESA), propanesulfonic acid (PSA), butanesulfonic acid (BSA), dodecanesulfonic acid (DDSA), cumenesulfonic acid (IPBSA), camphorsulfonic acid (CSA), hydroxyethanesulfonic acid (HESA), hydroxyethanedisulfonic acid (HEDSA), etc.

[0039] By containing the above crosslinking accelerator in the unfoamed rubber layer, the flexibility of the foamed rubber layer can be easily controlled, and a sealing material excellent in adhesion (sealing property) and resilience can be easily provided.

[0040] The foaming agent constituting the unfoamed rubber layer is not particularly limited, but is preferably a microcapsule in which a volatile liquid foaming agent is encapsulated with a thermoplastic shell polymer having gas barrier properties. When the above microcapsule is heated, the outer shell of the capsule softens, and the liquid foaming agent encapsulated in the capsule vaporizes, increasing the internal pressure. Due to such an action, the capsule expands to generate hollow spherical particles, and pores are formed in the foamed rubber layer by the hollow spherical particles.

[0041] Examples of the volatile liquid foaming agent constituting the microcapsule include low-boiling hydrocarbons such as isopentane, isobutane, and isopropane.

[0042] Examples of the thermoplastic shell polymer constituting the microcapsules include one or more selected from polyacrylonitrile, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-methyl methacrylate copolymer, vinylidene chloride-ethyl methacrylate, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-ethyl methacrylate, and the like.

[0043] When the unfoamed rubber layer contains the above microcapsules as a foaming agent, the foamability of the unfoamed rubber layer can be easily controlled, a foamed rubber layer having suitable flexibility can be easily formed, and a sealing material showing excellent adhesion (sealing property) even when the surface pressure is low can be easily provided.

[0044] The unfoamed rubber layer preferably contains the foaming agent in an amount of 1.0 to 10.0% by mass in terms of solid content, more preferably 2.0 to 8.0% by mass.

[0045] When the unfoamed rubber layer contains the foaming agent in the above ratio, the flexibility of the foamed rubber layer can be easily controlled, and a sealing material excellent in adhesion (sealing property) can be easily provided.

[0046] In the sealing material according to the present invention, when the elastic layer takes the second form, the elastic layer is composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a metal plate or a resin plate.

[0047] In the present application documents, the laminated integrated body means a state in which adjacent layers are chemically or physically fixed.

[0048] In the sealing material according to the present invention, the metal plate or resin plate constituting the base material layer is not particularly limited.

[0049] The metal plate constituting the base material layer is not particularly limited, and examples thereof include plate materials made of stainless steel (ferritic, martensitic, austenitic, etc.), iron, plated materials, aluminum, etc., and plate-like objects made of one or more metals selected from stainless steel or iron, etc. The metal plate constituting the base material layer may be one joined by laminating a plurality of metal plates, etc., and as such a metal plate, a bonded product of a stainless steel plate and an iron plate is preferable.

[0050] Examples of the resin plate constituting the base material layer include plate-like objects made of one or more resins selected from polyethylene (PE)-based resins, polypropylene (PP)-based resins, polyethylene terephthalate (PET)-based resins, polyethylene naphthalate (PEN)-based resins, polyvinyl chloride (PVC)-based resins, polystyrene (PS)-based resins, acrylic resins (PMMA), polycarbonate (PC)-based resins, polyphenylene sulfide (PPS)-based resins, polytetrafluoroethylene (PTFE)-based resins, polyether ether ketone (PEEK)-based resins, polyether sulfone (PES)-based resins, polyamide (PA)-based resins, polyimide (PI)-based resins, etc. Among the above-mentioned plate-like objects, as the resin plate constituting the base material layer, plate-like objects made of one or more resins selected from polyethylene terephthalate (PET)-based resins, polyethylene naphthalate (PEN)-based resins, polystyrene (PS)-based resins, polyphenylene sulfide (PPS)-based resins, polyether sulfone (PES)-based resins, etc. are preferable.

[0051] In the sealing material according to the present invention, the thickness of the metal plate or resin plate constituting the base material layer is not particularly limited, but is usually 1 to 500 μm.

[0052] In the present application documents, the thickness of the above-mentioned metal plate or resin plate means the arithmetic average value when the thicknesses at 10 locations are measured using a dial gauge.

[0053] In the sealing material according to the present invention, when the elastic layer adopts the second form, by having a base material layer made of a metal plate or a resin plate, the handleability of the sealing material can be easily improved.

[0054] In the sealing material according to the present invention, the elastic layer made of a foamed rubber layer is formed by dissolving a rubber compound containing a desired amount of ethylene-propylene-diene terpolymer (EPDM), a phenolic resin crosslinking agent, a crosslinking accelerator, a foaming agent, etc. in an organic solvent to form a coating solution, applying the coating solution onto the main surface of a suitable base material, fixing it to form an unfoamed rubber layer, and then heating this at a predetermined temperature for a predetermined time to cause foaming.

[0055] The foaming ratio can be easily controlled by adjusting the types and blending ratios of the rubber component constituting the rubber compound, the phenolic resin crosslinking agent, the crosslinking accelerator, and the foaming agent. In particular, it can be easily controlled by adjusting the crosslinking rate of EPDM which is the rubber component.

[0056] When the crosslinking rate is increased, crosslinking proceeds before the rubber component expands and deforms due to the foaming gas, so it becomes easier to suppress the foaming ratio. Conversely, when the crosslinking rate is decreased, the deformation of the rubber component due to the foaming gas takes precedence over the curing rate of the rubber due to crosslinking, so the foaming ratio tends to increase.

[0057] In the sealing material according to the present invention, when the elastic layer made of a foamed rubber layer adopts the first form, that is, the form consisting only of the foamed rubber layer, the above coating solution is applied onto the main surface of a suitable base material such as a metal plate or a resin plate, fixed to form an unfoamed rubber layer, then this is foamed to form a foamed rubber layer, and then this is peeled off from the base material layer to obtain the target elastic layer (the elastic layer consisting only of the foamed rubber layer).

[0058] In the sealing material according to the present invention, when the elastic layer made of a foamed rubber layer takes the second form, that is, a form composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a metal plate or a resin plate, the coating liquid is applied and fixed on both main surfaces of the base material layer made of a metal plate or a resin plate to form an unfoamed rubber layer, and then this is foamed to form a foamed rubber layer, whereby the target elastic layer (an elastic layer composed of a laminated integrated body in which foamed rubber layers are laminated and arranged on both main surfaces of a base material layer made of a metal plate or a resin plate) can be obtained.

[0059] The sealing material according to the present invention is one in which adhesive layers are further laminated and arranged on both main surfaces of the elastic layer. In the sealing material according to the present invention, the adhesive layer is formed by the adhesive constituting the adhesive layer adhering to the main surface of the elastic layer by its adhesive force.

[0060] The thickness of each of the above adhesive layers is preferably 1 to 100 μm, more preferably 5 to 70 μm, and even more preferably 10 to 60 μm. The thicknesses of the adhesive layers formed on both main surfaces of the elastic layer may be the same or different.

[0061] In the sealing material according to the present invention, when the thickness of the adhesive layer is within the above range, the desired adhesion (sealing property) can be easily exhibited.

[0062] The above thickness of the adhesive layer means the arithmetic average value when the thicknesses at 10 locations are measured using a dial gauge. In the sealing material according to the present invention, when the thickness of the adhesive layer is within the above range, the desired adhesion (sealing property) can be easily imparted to the sealing material.

[0063] In the sealing material according to the present invention, the adhesive layer preferably contains at least one selected from urethane resins, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene (SBR), nitrile rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), butyl rubber (IIR), chloroprene rubber (CR), thermoplastic elastomers, and water additives of any of the above.

[0064] In the sealing material according to the present invention, the thermoplastic elastomer is preferably at least one selected from styrenic thermoplastic elastomers, olefinic thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, ester-based thermoplastic elastomers, and amide-based thermoplastic elastomers.

[0065] In the sealing material according to the present invention, examples of the styrenic thermoplastic elastomer include copolymers of α-methylstyrene-ethylene-butylene-α-methylstyrene, triblock copolymers of styrene-butadiene-styrene, random copolymers of styrene-butadiene, block copolymers of styrene-isobutylene-styrene, hydrogenated products in which part or all of the carbon-carbon double bond portions of these copolymers such as styrene-butadiene-styrene (SBS) are hydrogenated, maleic anhydride-modified styrene-isoprene-styrene block copolymers, maleic anhydride-modified styrene-butadiene-styrene block copolymers (MAH-SBS), and the like. Examples of the hydrogenated product in which some or all of the carbon-carbon double bond portions of copolymers such as the above-mentioned styrene-butadiene-styrene (SBS) are hydrogenated include styrene-(ethylene / propylene)-styrene block copolymer (SEPS; hydrogenated product of SIS), styrene-(ethylene / butylene)-styrene block copolymer (SEBS; hydrogenated product of SBS), styrene-ethylene-(ethylene / propylene)-styrene block copolymer (SEEPS; hydrogenated product of styrene-butadiene / isoprene-styrene block copolymer), styrene-isobutylene-styrene block copolymer (SIBS), hydrogenated styrene butadiene (hydrogenated SBR), maleic anhydride-modified styrene-(ethylene / butylene)-styrene block copolymer (MAH-SEBS), maleic anhydride-modified styrene-(ethylene / propylene)-styrene block copolymer (MAH-SEPS), and the like. One or more selected therefrom may be mentioned.

[0066] In the sealing material according to the present invention, since the pressure-sensitive adhesive layer contains a thermoplastic elastomer as the pressure-sensitive adhesive, good sealing performance can be easily exhibited as compared with the case where there is no pressure-sensitive adhesive layer.

[0067] In the sealing material according to the present invention, the pressure-sensitive adhesive layer preferably contains 50 to 100% by mass, more preferably 60 to 90% by mass of the thermoplastic elastomer in terms of solid content.

[0068] In the sealing material according to the present invention, the pressure-sensitive adhesive layer can easily exhibit good sealing performance by containing the thermoplastic elastomer in the above ratio.

[0069] In the sealing material according to the present invention, the pressure-sensitive adhesive layer can be formed, for example, by applying a pressure-sensitive adhesive-containing liquid containing a thermoplastic elastomer on the main surface of the elastic layer obtained by the method described above.

[0070] According to the present invention, it is possible to provide a sealing material that exhibits high adhesion (sealing performance) at a low surface pressure.

[0071] Next, the present invention will be described in more detail with reference to examples, which are illustrative and do not limit the present invention.

[0072] (Example 1) (1) Preparation of elastic material As shown in Table 1, a hydrocarbon solvent was dissolved in a rubber compound kneaded with an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a filler, a phenolic resin crosslinking agent, a foaming agent, and an organic sulfonic acid as a crosslinking accelerator so that the content ratio of the phenolic resin crosslinking agent was 2.6% by mass to obtain a liquid of an unfoamed rubber composition. The obtained liquid of the unfoamed rubber composition was coated with a coater to a predetermined thickness and then dried at 60°C in a drying furnace to obtain an unfoamed rubber molded body with a thickness of 0.3 mm. The unfoamed rubber molded body obtained by the above drying treatment was heat-treated in an oven at 180°C to be crosslinked and foamed, thereby producing an elastic material foamed to a foaming ratio of 2.7 times. The manufacturing conditions are shown in Table 1. In addition, a rubber compound not containing a foaming agent was prepared in the above rubber compound, and the torque change of an uncrosslinked rubber molded body with a thickness of 3 mm molded using the obtained rubber compound was measured by a moving die rheometer (MDR) in the following manner. The results are shown in Table 1.

[0073] ><Measurement of torque change by moving die rheometer (MDR)> In the above uncrosslinked rubber molded body, based on the provisions of JIS K6300-2, the torque change over time was measured using a moving die rheometer (MDR). The results are shown in Table 1. M shown in Table 1 is the torque value 15 minutes after the start of vulcanization measured by the above method. Since the torque increases as the crosslinking of the above uncrosslinked rubber molded body progresses, the value of M becomes an index of the degree of crosslinking. The higher the value of M, the more it means that a crosslinked rubber molded body with a higher crosslink density is obtained. From this, it means that even in an elastic material obtained by crosslinking and foaming an unfoamed rubber molded body having the same composition except for containing an uncrosslinked rubber molded body and a foaming agent, the crosslink density of the foamed rubber constituting the elastic material increases, making it easier to reduce stress relaxation when used as a sealing material and showing excellent sealing performance.

[0074] (2) Application of Adhesive A thermoplastic elastomer adhesive liquid, which is an adhesive, was applied in a predetermined amount to both main surfaces of the elastic material made of the foamed rubber obtained in (1) using a coater, and dried in a drying furnace, thereby forming adhesive layers on both main surfaces of the elastic material to obtain the target sealing material. The stress relaxation rate and gas leakage property of the obtained sealing material were measured by the following methods. The results are shown in Table 1.

[0075] <Measurement of Stress Relaxation Rate> A sample obtained by punching out the obtained sealing material into a donut shape with an inner diameter of 10 mm and an outer diameter of 20 mm was sandwiched between upper and lower flanges by a commercially available compression-tension testing machine (Autograph AG50kGN, manufactured by Shimadzu Corporation), compressed at an initial surface pressure of 1.0 MPa, and maintained at 25°C for 3.5 hours. Then, the surface pressure at the time when 3.5 hours had elapsed since the start of compression was measured. Then, the stress relaxation rate was determined by the following formula. Stress relaxation rate = (Initial surface pressure - Surface pressure at the time of 3.5 hours after the start of compression) ÷ Initial surface pressure × 100 (%) The stress relaxation rate is an index of the sealing performance of the sealing material. When the sealing material is tightened at a predetermined tightening surface pressure, it indicates the reduction ratio of the tightening surface pressure at the time when a predetermined time has elapsed since the start of tightening. The smaller the stress relaxation rate of the sealing material, the less the sealing performance of the sealing material deteriorates over time, meaning that the sealing performance is excellent.

[0076] <Evaluation of Gas Leakage Property> Next, air gas was injected into the donut-shaped sample sandwiched and crimped between the upper and lower flanges described above so that a predetermined gas pressure (0.3 to 0.5 MPa) was applied, and a seal test was carried out. The sealing performance was evaluated by checking the pressure (MPa) applied to the sealing material with a pressure meter and confirming the presence or absence of gas leakage. The results are shown in Table 1.

[0077] (Examples 2 to 7, Comparative Examples 1 to 4) (1) Preparation of elastic material In the “(1) Preparation of elastic material” of Example 1, except that the compounding ratio in terms of solid content of the phenolic resin crosslinking agent in the rubber compound and the type of crosslinking accelerator to be compounded were changed as shown in Table 1, after obtaining an unfoamed rubber molded body in the same manner as in Example 1, crosslinking and foaming were carried out so as to obtain the foaming ratio shown in Table 1 to produce an elastic material. The manufacturing conditions are shown in Table 1. Also, the torque value (dN·m) of the uncrosslinked rubber molded body prepared in the same manner as in Example 1 was measured by a moving die rheometer (MDR) in the same manner as in Example 1. The results are shown in Table 1.

[0078] On both main surfaces of each elastic material made of foamed rubber obtained in Examples 2 to 7 and Comparative Examples 1 to 4, a thermoplastic elastomer adhesive liquid, which is an adhesive, was applied in a predetermined amount using a coater in the same manner as in Example 1(2), and dried in a drying furnace, whereby adhesive layers were formed on both main surfaces of the elastic material, respectively, to obtain the target sealing material. Also, in Comparative Example 1, the elastic material prepared in (1) above was used as the sealing material as it was without applying an adhesive layer. The stress relaxation rate and gas leakage property of the obtained sealing material were measured by the same method as in Example 1. The results are shown in Table 1. In addition, the crosslinking accelerators described in Table 1 by abbreviations mean the following compounds, respectively. PTSA: p-toluenesulfonic acid DNNDSA: dinonylnaphthalenedisulfonic acid DDBSA: dodecylbenzenesulfonic acid DNNSA: Dinonylnaphthalenesulfonic acid

[0079]

Table 1

[0080] The sealing materials according to the present invention obtained in Examples 1 to 7 have an elastic material made of a foamed rubber and adhesive layers laminated on both main surfaces of the elastic material, and the foamed rubber is composed of a crosslinked and foamed body of an unfoamed rubber molded body containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator composed of an organic sulfonic acid compound, and a foaming agent. Therefore, as shown in Table 1, the uncrosslinked rubber molded bodies prepared in Examples 1 to 7 have a high torque value M and a high crosslinking density when measuring the torque change by MDR, so it is considered that when the obtained elastic material is used as a sealing material, it exhibits excellent sealing performance capable of reducing stress relaxation. Actually, as shown in Table 1, the sealing materials according to the present invention obtained in Examples 1 to 7 have a low stress relaxation rate even when the surface pressure is low, and it can be seen that they can exhibit excellent adhesion (sealing performance) without gas leakage when evaluating the gas leakage property.

[0081] On the other hand, the sealing material obtained in Comparative Example 1 does not contain an adhesive layer (consists only of an elastic material). Therefore, as shown in Table 1, it can be seen that the sealing material obtained in Comparative Example 1 has a higher stress relaxation rate compared to the sealing material having the adhesive layer obtained in Example 1, and it can be seen that it is inferior in adhesion (sealing performance) causing gas leakage when evaluating the gas leakage property.

[0082] In addition, the sealing materials obtained in Comparative Examples 2 to 4 are composed of a crosslinked and foamed body of an unfoamed rubber molded body in which the foamed rubber constituting the elastic material does not contain a crosslinking accelerator composed of an organic sulfonic acid compound. Therefore, it can be seen that the stress relaxation rate is higher compared to the sealing materials having an adhesive layer obtained in Example 3 and Examples 5 to 7, and it can be seen that the adhesion (sealing property) is inferior and gas leakage occurs when evaluating the gas leakage property.

Industrial Applicability

[0083] According to the present invention, it is possible to provide a sealing material that exhibits high adhesion (sealing property) at a low surface pressure.

Explanation of Symbols

[0084] 1 Sealing material i Elastic layer r Foamed rubber layer s Adhesive layer b Base material layer

Claims

1. An elastic layer including a foamed rubber layer, and adhesive layers laminated on both main surfaces of the elastic layer respectively, wherein the foamed rubber layer is composed of a foam of an unfoamed rubber layer containing an ethylene-propylene-diene terpolymer (EPDM) as a rubber component, a phenolic resin crosslinking agent, a crosslinking accelerator, and a foaming agent, and the crosslinking accelerator is an organic sulfonic acid compound characterizing the sealing material.

2. The sealing material according to Claim 1, wherein the content ratio of the phenolic resin crosslinking agent in the unfoamed rubber layer is 2.0 to 20.0% by mass in terms of solid content.

3. The sealing material according to Claim 1, wherein the elastic layer consists only of the foamed rubber layer or is a laminated integrated product in which the foamed rubber layer is laminated on both main surfaces of a base material layer made of a metal plate or a resin plate respectively.

4. The sealing material according to Claim 1, wherein the diene amount constituting the ethylene-propylene-diene terpolymer (EPDM) is 1 to 20% by mass.

5. The sealing material according to Claim 1, wherein the foamed rubber layer is a foam with a foaming ratio of 1.5 times or more of the unfoamed rubber layer.

6. The sealing material according to Claim 1, wherein the adhesive layer contains at least one selected from urethane resin, natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene, nitrile rubber, ethylene-propylene-diene terpolymer, butyl rubber, chloroprene rubber, thermoplastic elastomer, and any water addition products thereof as the adhesive.

7. The sealing material according to Claim 6, wherein the thermoplastic elastomer is at least one selected from styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, ester-based thermoplastic elastomer, and amide-based thermoplastic elastomer.

Images